Previous Article | Next Article 
Antimicrobial Agents and Chemotherapy, June 2000, p. 1549-1555, Vol. 44, No. 6
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
A New Class of Genetic Element, Staphylococcus
Cassette Chromosome mec, Encodes Methicillin Resistance
in Staphylococcus aureus
Y.
Katayama,
T.
Ito, and
K.
Hiramatsu*
Department of Bacteriology, Juntendo
University, Tokyo, Japan
Received 10 December 1999/Returned for modification 30 January
2000/Accepted 10 March 2000
 |
ABSTRACT |
We have previously shown that the methicillin-resistance gene
mecA of Staphylococcus aureus strain N315 is
localized within a large (52-kb) DNA cassette (designated the
staphylococcal cassette chromosome mec
[SCCmec]) inserted in the chromosome. By
sequence determination of the entire DNA, we identified two novel genes (designated cassette chromosome recombinase genes [ccrA
and ccrB]) encoding polypeptides having a partial homology
to recombinases of the invertase/resolvase family. The open reading
frames were found to catalyze precise excision of the
SCCmec from the methicillin-resistant S. aureus
chromosome and site-specific as well as orientation-specific integration of the SCCmec into the S. aureus
chromosome when introduced into the cells as a recombinant multicopy
plasmid. We propose that SCCmec driven by a novel set of
recombinases represents a new family of staphylococcal genomic elements.
 |
INTRODUCTION |
Methicillin-resistant
Staphylococcus aureus (MRSA) was first isolated in England
in 1961 shortly after the development of methicillin, the first
penicillinase-resistant semisynthetic penicillin (15). Since
then, MRSA has become the most prevalent pathogen causing hospital
infection throughout the world, and MRSA incidence is still increasing
in many countries (1). MRSA is resistant to practically all
-lactam antibiotics, a class of antibiotics represented by
penicillins and cephalosporins (3).
The
-lactam resistance of MRSA is caused by the production of a
novel penicillin-binding protein (PBP) designated PBP 2' (or PBP 2a),
which, unlike the intrinsic set of PBPs (PBP 1 to 4) of S. aureus, has remarkably reduced binding affinities to
-lactam
antibiotics (9, 24, 30). Despite the presence of otherwise
inhibitory concentrations of
-lactam antibiotics, MRSA can
continue cell wall synthesis solely depending upon the uninhibited
activity of PBP 2' (21). PBP 2' is encoded by a mecA gene located on the chromosome of MRSA. In 1987, the
mecA gene was cloned from a Japanese MRSA strain, and
its sequence was determined (20, 26). The
mecA gene is widely distributed among S. aureus as well as coagulase-negative staphylococci (13, 28). Therefore, it has been speculated that the methicillin resistance determinant (mec determinant) is freely
transmissible among staphylococcal species. However, with a detailed
molecular epidemiological study, Kreiswirth et al. have proposed that
MRSA originated from a single or two ancestral clones (16).
This led to the view that the frequency of inter- or intraspecies
transmission of mecA is a rather limited process and that
mec transmission may not be due to specialized transmission
machinery, such as a transposon.
We have recently cloned and sequenced the entire chromosomal region
surrounding the mecA gene, which is additionally present in
the MRSA chromosome and is absent from the chromosome of
methicillin-susceptible S. aureus (MSSA) (referred to
herein as mecDNA), from a Japanese pre-MRSA strain,
N315 (10). We identified the mecDNA-S.
aureus chromosome junction points and the overall
structure of mecDNA, and revealed that
mecDNA constitutes a genomic island or
antibiotic resistance island of S. aureus (14).
In this study, based on the structure of mecDNA, we
report that mecDNA is a new class of genomic element
designated SCCmec (for staphylococcal cassette chromosome mec [12]) driven by two
site-specific recombinase genes designated ccrA and
ccrB (for cassette chromosome recombinases A and B).
 |
MATERIALS AND METHODS |
Bacteria and growth condition.
Pre-MRSA strain N315 and its
SCCmec excising strain N315ex used in this study
have been described previously (14). All the strains and
their transformants were cultivated in brain heart infusion (BHI) broth
(Becton Dickinson Microbiology Systems, Sparks, Md.). The antibiotics
tetracycline (Sigma Chemical Co., St. Louis, Mo.) and tobramycin
(Shionogi Co., Osaka, Japan) were used at the concentration of 10 µg/ml.
Construction of recombinant plasmids.
Recombinant plasmid
pSR harboring intact ccrA and ccrB genes was
constructed by cloning the BamHI-digested DNA fragment
containing ccr genes into the unique BamHI site
of the plasmid vector pYT3 (8). The DNA fragment containing
ccr genes was prepared by PCR using the DNA extracted from
N315 as a template. The two primers used were
5'-AAAAGGATCCATTAGCCGATTTGGTAATTGAA-3' and
5'-AAAAGGATCCTCTGCTTCTTCGAATCTGCAAAT-3' (introduced BamHI sites are underlined), which
correspond to the nucleotides from base positions 24,004 to 24,025, and
to the complementary nucleotides from positions 27,365 to 27,343 of the
SCCmec sequence (accession no. D86934),
respectively. To construct pSRA*, the BamHI fragment of pSR
was subcloned into the BamHI site of pUC119
H, a
derivative of pUC119 whose HindIII site had been
eliminated by treatment with the Klenow fragment of DNA polymerase I
and self-ligation. The resultant plasmid, pUCSR, was digested with BalI and HindIII and flush ended by Klenow
treatment, which was followed by ligation to delete the
BalI-HindIII fragment (344 bp) of the
ccrA gene. Then, the BamHI fragment was cut out
of the plasmid and was ligated into the BamHI site of pYT3
to obtain pSRA*. To construct pSRB*, pUCSR was cut with
BstXI and MluI to remove the 252-bp
BstXI-MluI fragment of the ccrB gene,
and this was followed by Klenow treatment and self-ligation. The
BamHI fragment of the resultant plasmid was cut out and
ligated into the BamHI site of pYT3 to obtain pSRB*.
To construct attSCC-containing recombinant
plasmids, the DNA fragment containing the attSCC
sequence on the putative closed circular SCCmec
cassette was amplified by PCR using the two primers mR7 and mL2 (see
below), and the DNA was extracted from N315 (pSR) and used as a
template. The amplified DNA was digested with SalI, and the
resultant 933-bp fragment was cloned into a unique SalI site
of plasmid pYT3 to obtain pYT3att. Then, the
attSCC fragment was cut out of pYT3att with
SalI and introduced into the SalI sites of
pSR, pSRA*, and pSRB* to obtain pSRatt, pSRA*att, and pSRB*att, respectively.
Nucleotide sequencing.
The DNA fragments for sequencing were
obtained by PCR amplification with genomic DNA as templates.
After purification using a QIAquick PCR purification kit (QIAGEN,
Hilden, Germany), the fragments of PCR products were directly sequenced
with a set of synthetic oligonucleotide primers (see below) using a
dye-labeled terminator-Taq DNA polymerase cycle sequencing
kit (Applied Biosystems Inc., Foster City, Calif.). The sequence was
read on a 373A automated fluorescent DNA sequencing system
(Perkin-Elmer, Foster City, Calif.). All the computer analyses of
nucleotide sequences were carried out using programs in The Wisconsin
Package (version 9.0; Genetics Computer Group [GCG], Madison, Wis.).
A homology search was performed using BLAST and TFastA programs
accessed via the EMBL (release no. 55.0) and GenBank (release no.
107.0) databases and the FastA program accessed via the SWISS-PROT
database. (release no. 35.0).
PFGE.
Pulsed-field gel electrophoresis (PFGE) was performed
with a modification as described previously (32). For
preparation of sample plugs, ca. 2 × 106 cells were
embedded in 37.5 µl (1.5 by 5 by 5 mm) of 1% (wt/vol) low-temperature-melting agarose (Agarose Low Melt Preparative Grade;
Bio-Rad Laboratories, Hercules, Calif.) containing 40 µg of
lysostaphin (Sigma Chemical Co.) per ml. The sample plugs were incubated with 1% (wt/vol) N-lauroylsarcosine (Sigma
Chemical Co.)-0.5 M EDTA, pH 7.5, at 37°C for 1 h and further
incubated with a solution containing 2 mg of proteinase K (Sigma
Chemical Co.) per ml, 1% (wt/vol) N-lauroylsarcosine (Sigma
Chemical Co.), and 0.5 M EDTA, pH 7.5, at 50°C for 24 h. The
plugs were then incubated with 1 mM phenylmethylsulfonyl fluoride
(Sigma Chemical Co.) at 50°C for 30 min, followed by washing three
times with Tris-EDTA (20 min each at 4°C). The samples were then
treated with 60 U of SmaI (Takara Shuzo Co. Ltd., Kyoto,
Japan) at 30°C for 24 h and next were treated with 200 µg of
proteinase K at 37°C for 1 h. The final concentrations of
SmaI and proteinase K were 0.4 U/µl and 100 µg/ml,
respectively. They were further washed three times with Tris-EDTA at
4°C for 20 min and subjected to PFGE with 1.2% agarose gel
(high-strength analysis-grade agarose; Bio-Rad Laboratories). The
PFGE was performed at 4°C for 20 h in 0.5× Tris-borate-EDTA
running buffer using a CHEF DRII apparatus (Bio-Rad Laboratories) with
an electric field strength of ~6 V/cm and a pulse time of 20 s.
Electroporation.
Exponentially growing cultures of strain
N315 or N315ex were harvested at an optical density at 600 nm of 0.5 and washed with prechilled 1.1 M sucrose three times. The pellet was
resuspended in 100 µl of EP buffer (1.1 M sucrose, 2 mM
MgCl2, 14 mM
KH2PO4-Na2HPO4 [pH
7.4]). To the cell suspension, 5 µg of the plasmid DNA was added,
and the mixture was kept on ice for 25 min. An electric pulse of 25 µF, 2.5 kV, and 100
was delivered by a Gene Pulser (Nippon
Bio-Rad Laboratories, Tokyo, Japan). The cells were then transferred
into 0.5 ml of 1.1 M sucrose in BHI broth and incubated for 2 h at
30°C (permissive temperature for plasmid replication) before aliquots
were plated on BHI agar plates containing tetracycline (10 µg/ml).
After a 48-h incubation at 30°C, mature colonies were picked and
subjected to rapid plasmid analysis by digestion with various
restriction enzymes to confirm the integrity of the introduced plasmid.
The plasmid preparation procedure has been described previously
(32). The transformants were further colony purified by
streaking them onto the BHI agar plate with tetracycline (10 µg/ml)
and incubating the plate overnight before establishing the transformant
strains as those used in this study.
Southern blot hybridization.
Southern transfer of DNA from
the PFGE gel to a nylon membrane was performed as described previously
(32). Hybridization took place in a hybridization solution
(50% formamide, 5× SSC [1× SSC is 0.15 M NaCl plus 0.015 M sodium
citrate], 0.3% sodium dodecyl sulfate [SDS], 2% blocking reagent
[Boehringer, Mannheim, Germany]) containing 20 ng of
digoxigenin-labeled DNA probe per ml. Incubation was carried out for
16 h at 42°C. The orfX probe was prepared by using
primers 5'-CCACGCATAATCTTAAATGCTCT-3' and 5'-AAACGACATGAAAATCACCAT-3' (primer cR2
[14]), which corresponded to the nucleotides from base
positions 56,357 to 56,379 and complementary nucleotides from base
positions 56,824 to 56,804 of the reported nucleotide sequence of
orfX (accession no. D86934), respectively. The probe for the
ermA gene was prepared using synthetic oligonucleotides 5'-TGAAACAATTTGTAACTATTGA-3' and
5'-TGAACCAGAAAAACCCTAAAGA-3' as primers, which corresponded
to the nucleotides from positions 33,804 to 33,825 and the
complementary nucleotides from position 34,530 to 34,509, respectively,
of the reported nucleotide sequence of the N315
SCCmec (accession no. D86934
[14]). The cloned DNA fragment SJ2, which contains
Tn554 of SCCmec, was used as the
template for the PCR amplification of the ermA gene
(14). These probes were labeled with digoxigenin using a DNA
labeling kit (Boehringer). The hybridized filter (Biodyne A; Pall
Biosupport Co., Glen Cove, N.Y.) was washed twice in 2× SSC with 0.1%
SDS for 5 min at room temperature and then in 1× SSC with 0.1% SDS for 15 min at 68°C. Visualization of the signal was achieved using an
alkaline phosphatase-conjugated antidigoxigenin antibody (Boehringer) and the chemiluminescent substrate CSPD (Boehringer) according to the
procedure recommended by the manufacturers.
Synthetic oligonucleotides used as primers for PCR and nucleotide
sequencing.
The primers used in this study and their nucleotide
sequences with references, if not specified above, are listed below in the order of appearance in the text: cL1,
5'-ATTTAATGTCCACCATTTAACA-3' (14); mL1,
5'-GAATCTTCAGCATGTGATTTA-3' (corresponds to the
complementary nucleotides from positions 4,977 to 4,957 of the
nucleotide sequence [accession no. D86934]); mR8,
5'-ATGAAAGACTGCGGAGGCTAACT-3' (corresponds to the
nucleotides from base position 56,636 to 56,658 [accession no.
D86934]); cR2, 5'-AAACGACATGAAAATCACCAT-3' (14); mA1, 5'-TGCTATCCACCCTCAAACAGG-3' (10); mA2,
5'-AACGTTGTAACCACCCCAAGA-3' (10); mR7,
5'-AAAAAGTCGACACTGCTTGGGTAACTTATCATGGA-3'; mL2,
5'-AAAAAGTCGACATCACAGTAGTGCAAAGCACGTCGA-3';
,
5'-TTTCACACAGGAAACAGCTATGAC-3'; and
,
5'-ATCACGATATTGCTTATAAGCA-3' (corresponds to the nucleotides
from base positions 26,673 to 26,694 of the reported sequence
[accession no. D86934]).
 |
RESULTS |
ccrA and ccrB gene-mediated excision of
SCCmec.
Two novel ORFs, ccrA and
ccrB, were located in the midst of
SCCmec (Fig.
1A). CcrA and CcrB
polypeptides of 449 and 542 amino acids were potentially encoded by the
ORFs. A Shine-Dalgarno sequence and
10 and
35 presumptive promoter
sequences were identified immediately upstream of ccrA. On
the other hand, although Shine-Dalgarno sequence was found for
ccrB, no candidates for promoter sequences were identified
in the adjacent upstream region of the gene. This suggests that the two
ORFs may be transcribed as a single mRNA.



View larger version (127317K):
[in this window]
[in a new window]
|
FIG. 1.
Identification of ccr genes. (A) Genomic
structure of SCCmec. Locations of the essential
genes are illustrated. The left and right
chromosome-SCCmec junctions, attL and
attR, were tentatively and operationally defined in this
study by PCR primer combinations of cL1 and mL1 for attL,
and mR8 and cR2 for attR. The MSSA chromosomal parts of the
attL and attR were defined as attB-L
and attB-R, delimited by primers cL1 and cR2, respectively.
The SCCmec parts of these elements were defined as
attSCC-L and attSCC-R,
delimited by the primers mL1 and mR8, respectively: i.e.,
attL is attB-L plus
attSCC-L, and attR is attB-R
plus attSCC-R. Transposon Tn554
(23), encoding resistance to erythromycin and spectinomycin,
was located in upstream of the mecI-mecR1-mecA gene complex
(14). Plasmid pUB110, encoding resistance for
kanamycin-tobramycin and bleomycin, was inserted between two insertion
sequences IS431 (or IS257) (2, 7, 14, 22,
27). Nucleotide sequences around the left and right boundaries of
SCCmec, attL and attR, are
shown at the bottom of the panel. Inverted repeats, IRscc-L and
IRscc-R, at both extremities of SCCmec are
indicated by thin arrows. Thick arrows indicate the direct repeats,
DR-B and DR-SCC. The nucleotide sequence of the N315
chromosome containing the entire SCCmec (56,939 bp) is deposited in DDBJ/EMBL/GenBank under accession number D86934.
(B) Deduced amino acid sequences of ccrA and
ccrB. CcrA and CcrB amino acid sequence were aligned with
that of TP901-1 integrase (4). The alignment was performed
using the Pile-Up program with a scoring matrix of pam 250 in the
Wisconsin Package (version 9.0; Genetics Computer Group). Amino acids
shared by the three peptides are boxed in red. CcrA and CcrB had 26.5 and 37.4% amino acid identity, respectively, with the TNP901-1
integrase. Large bullets indicate amino acid residues of CcrA or CcrB
shared by site-specific recombinases of the invertase/resolvase family.
Small bullets indicate amino acid substitution within the same class of
amino acids. Of the 64 amino acid positions well conserved among the
recombinases of the invertase/resolvase family (shown in pink)
(25), 44 and 47 amino acids, respectively, were conserved in
CcrA and CcrB. An arrowhead indicates the presumptive serine involved
in the 5' phosphoseryl linkage of the recombinase to DNA
characteristically conserved in the NH2-terminal catalytic
domain of site-specific recombinases of the invertase/resolvase family
(25). (C) Construction of plasmids carrying intact and
disrupted ccr genes. Restriction maps of pSR, pSRA* (a
derivative of pSR with a partially deleted ccrA), and pSRB*
(a derivative of pSR with a partially deleted ccrB) are
shown. Arrows indicate the direction of transcription of the structural
gene ccr and tetL. The respective set of
ccrA and ccrB genes was inserted at the
BamHI site of pYT3.
|
|
Two ORFs,
ccrA and
ccrB, were subcloned into a
shuttle vector, pYT3, which has a temperature-sensitive origin of
replication
(copy numbers: 14 at 30°C, 1 at 37°C, and 0 at 42°C).
The recombinant
plasmids obtained were pSR, pSRA* (with a deletion
introduced
in
ccrA), and pSRB* (with a deletion introduced
in
ccrB) (Fig.
1C). These recombinant plasmids were
introduced into N315 by electroporation
(
17).
After cultivation of these strains in drug-free broth for 20 h at
30°C, we evaluated the proportion of the cells which had
lost
SCC
mec in the culture by plating onto agar with
and without
tobramycin. The cultures of strains N315, N315(pYT3),
N315(pSRA*),
and N315(pSRB*) yielded essentially equal numbers of
colonies
on the BHI agar plates with or without tobramycin. On the
other
hand, the culture of strain N315(pSR), harboring
both intact
ccrA and
ccrB genes, generated
tobramycin-susceptible cells, which
constituted 51 to 62% of the
entire cell population in repeated
experiments. A representative
tobramycin-susceptible subclone,
N315ex was established from the
experiment.
Antibiotic susceptibility patterns of N315 and N315ex were compared on
the basis of MICs determined using a standard procedure
(
17). The MICs of various antibiotics (in micrograms per
milliliter)
for N315 and N315ex were, respectively, 64 and 2 (oxacillin),
64 and 4 (ceftizoxime), 256 and 0.5 (tobramycin), 256 and
2 (kanamycin),
and >512 and 16 (bleomycin). The data showed that all
the resistance
phenotypes were associated with the presence of
SCC
mec except
for erythromycin resistance.
Southern blot hybridization analysis
of
SmaI-digested DNAs
of N315 and N315ex using the
ermA gene-specific
probe
detected four restriction fragments (>436.5, 420, 320, and
110 kb in
size) in both strains in addition to the 215-kb fragment
of N315 on
which SCC
mec was localized (data not shown; see
below
for the PFGE-separated
SmaI-restriction fragment
pattern).
To confirm that the loss of resistance was caused by the excision of
SCC
mec, DNAs were extracted from transformants
N315(pYT3),
N315(pSR), N315(pSRA*), and N315(pSRB*), as
well as from control
strains N315 and N315ex. PCR using the combination
of primers
cL1 and cR2, which theoretically amplifies the 0.5-kb
DNA fragment
containing
attB when
SCC
mec is excised from the chromosome
[Fig.
2A), did not amplify any DNA
fragment with N315, N315(pYT3), N315(pSRA*),
and
N315(pSRB*) DNAs as templates but the 0.5-kb DNA fragment
was
amplified with DNAs extracted from N315(pSR) and N315ex (Fig.
2A).
The nucleotide sequencing of the amplified 0.5-kb DNA fragments
from
both N315(pSR) and N315ex DNAs showed that they contained
the
attB sequence theoretically expected to be generated by the
precise excision of SCC
mec from the chromosome
(Fig.
2B). The
SCC
mec excision was considered to
be precise since the nucleotide
sequencing using the total DNA
extracted from N315(pSR) as a template
yielded a readable
nucleotide sequence of
attB which was identical
to that
yielded when the N315ex DNA was used as a template.

View larger version (33K):
[in this window]
[in a new window]
|
FIG. 2.
Precise excision of SCCmec mediated
by ccrA and ccrB. (A) Detection of
ccr-mediated SCCmec excision and
appearance of attSCC. Template DNAs for PCR were
extracted from overnight culture of the colony purified transformant
strains in BHI broth with tetracycline (10 µg/ml). Four sets of
primers were used to detect precise excision and the closed circle form
of SCCmec. Primers cR2 and cL1 were used to detect
attB (549 bp). Primers mL1 and mR8 were used to identify
attSCC (456 bp). Primers cL1 and mL1 were used to
detect attL (371 bp). Primers mA1 and mA2 were used to
detect a part of mecA gene (286 bp). Note that precise
excision of SCCmec occurred only in N315(pSR)
and N315ex and that attSCC was detected only in
N315(pSR). The molecular weight marker was a 1-kb ladder
(Gibco-BRL, Gaithersburg, Md.) and only the relevant sizes are
indicated. (B) Generation of attSCC and
attB. The presumptive closed circular form of
SCCmec is illustrated with
attSCC, which appeared to be generated by
head-to-tail ligation of attSCC-L (stippled box) and
attSCC-R (striped box) (see Fig. 1A). Nucleotide sequences of
attB in amplified DNA fragments from N315ex and
N315(pSR) are also illustrated. The primers mR7 and mL2 were used
for the cloning of attSCC into pYT3.
|
|
Concomitant appearance of a rearranged attachment sequence,
attSCC, with SCCmec
excision.
Upon the precise excision, the excised
SCCmec was expected to form an extrachromosomal
closed circular DNA. To test this possibility, PCR was performed using
a pair of primers set divergently at both termini of
SCCmec (primers mR8 and mL1 [Fig. 1A]). Figure
2A shows that a DNA fragment of 0.5 kb was specifically amplified from N315(pSR) but not from the other test strains. Nucleotide
sequencing of the fragment showed a novel nucleotide sequence
presumably generated by a head-to-tail ligation of
attSCC-R and attSCC-L of both
termini of SCCmec, forming a novel attachment
sequence designated attSCC (Fig. 2B). The
divergently arranged 27-bp inverted repeats, IR-L and IR-R, with a core
of four nucleotides, TTCT (underlined in Fig. 2B), between them and the
presence of direct repeats, DR-SCC, were characteristic of
the structure of the attSCC. The data suggested
that a closed circular form of SCCmec was produced as a result of the precise excision of SCCmec from
the N315 chromosome.
Loss of SCCmec during passage of
N315(pSR).
To see the rate of loss of
SCCmec from the culture of N315(pSR) and
confirm the precision of excision mediated by ccr genes, PFGE analysis on the total DNAs that were consecutively extracted from
the culture was performed (Fig. 3A).
Compared to the culture of N315 and N315(pYT3) (lanes 1 and 9, respectively), N315(pSR) had an extra band of about 160-kb (Fig.
3A, lane 2). The band was indistinguishable from that of N315ex, from
which a 215-kb band of N315 was missing (lane 8). As long as the
N315(pSR) was cultured in tobramycin-containing BHI broth, the
proportions of the two bands were the same: densitometric measurement
of the 215-, and 160-kb bands yielded a ratio of about 7 to 8:1 (data not shown). When, the cells were washed and resuspended in BHI broth
without tobramycin, the intensity of the 215-kb band of N315(pSR)
started decreasing and continued to do so during the course of the
passage, while the 160-kb band continued increasing in intensity (Fig.
3A, lanes 2 to 7). Southern blot hybridization of the PFGE bands using
orfX DNA as a probe showed that both the 215- and 160-kb
bands carried orfX (Fig. 3B). Rehybridization of the
membrane using the mecA gene probe showed that the 215-kb band hybridized with the probe, but the 160-kb band did not (data not
shown). This clearly showed that the loss of mecA gene was caused by the precise excision of SCCmec. Greater
than 99% of the cells in culture became susceptible to tobramycin and
methicillin after 10 days' passage of N315(pSR) without
tobramycin.

View larger version (68K):
[in this window]
[in a new window]
|
FIG. 3.
Loss of SCCmec during the
cultivation of N315(pSR). (A) PFGE banding patterns of
SmaI-digested total DNAs extracted from N315(pSR) on
different days of passage. (B) Southern blot hybridization of the DNA
fragments of the gel in panel A after transfer to a sheet of nylon
membrane. The probe used was orfX. Lanes: 1, N315 cultivated
for 24 h with tobramycin (10 µg/ml); 2, N315(pSR) cultivated
for 24 h with tobramycin; 3 to 7, N315(pSR) after cultivation
without tobramycin for 1, 4, 5, 7, and 9 days, respectively; 8, N315ex
cultivated for 24 h without tobramycin; 9, N315(pYT3)
cultivated for 24 h with tobramycin; 10, lambda DNA marker for
PFGE (lambda ladder; Bio-Rad Laboratories). The sizes of the marker DNA
(from top to bottom) were 485.0, 436.5, 388.0, 339.5, 291.0, 242.5, 194.0, 145.5, 97.0, and 48.5 kb. The arrows at the side of each figure
indicate the DNA fragments hybridizable with the orfX
probe.
|
|
Site-specific, orientation-specific integration of experimental
plasmid mediated by ccr genes.
To investigate whether
the putative closed circular form of SCCmec serves
as a substrate for integration when introduced into a MSSA cell, we
constructed experimental plasmids pSRatt and pSRtta on which both
ccr genes and the presumptive attachment sequence, attSCC, are subcloned (14).
The plasmid pSRtta was identical with pSRatt except that the
attSCC fragment was cloned in the opposite
orientation (Fig. 4). The resultant
recombinant plasmids were introduced into strain N315ex by
electroporation, and transformants were selected by overnight
incubation on BHI agar plates containing tetracycline (10 µg/ml) at
30°C. The colony of each transformant was respread onto BHI agar
plates containing tetracycline (10 µg/ml) and incubated overnight at
30 or 43°C (nonpermissive temperature for the plasmid replication)
before enumeration of the generated colonies. Two strains,
N315ex(pSRatt) and N315ex(pSRtta), generated significant number of
colonies at 43°C, i.e., 17.7 and 21.2%, respectively, of those grown
at 30°C, whereas the other strains generated only small number of
colonies; i.e., <0.001% of those grown at 30°C. The result showed
that the chromosomal integration of the plasmids occurred only when
attSCC and an intact set of ccrA and
ccrB genes were present on the plasmids.

View larger version (44K):
[in this window]
[in a new window]
|
FIG. 4.
Site-, and orientation-specific integration
of experimental plasmids mediated by ccrA and
ccrB. PCR detection of the left and right plasmid-chromosome
junctions was performed with four crisscross combinations of primers
with DNAs extracted from the culture of N315ex(pSRatt),
N315ex(pSRtta), and N315ex(pYT3att) as templates. Four primers
L (cL1; see Fig. 1A), R (cR2; see Fig. 1A), , and were used. The
location and direction of the four primers are illustrated. Only the
regions adjacent to the introduced attSCC on the
plasmids and the attB on N315ex chromosome are illustrated.
The expected sizes of the amplified DNA fragments generated by a
site-specific integration of the plasmids were 610 bp (L- ), 1,255 bp
(L- ), 1,649 bp (R- ), 1004 bp (R- ), and 549 bp (L-R). The
results show a strict site and orientation specificity of
ccr-mediated integration. The molecular weight marker used
was a 1-kb ladder.
|
|
To learn whether the integration of the experimental plasmids was site-
and orientation-specific, i.e., whether a strand exchange
occurs
between the
attB site of the chromosome and the
attSCC
site of pSRatt in a fixed orientation, a
crisscross PCR experiment
was designed (Fig.
4). The cultures of
transformants N315ex(pSRatt)
and N315ex(pSRtta), with
N315ex(pYT3att) as a control, were analyzed
with PCR amplification
using crisscross combinations of four primers:
L (cL1) and R (cR2)
flanking the
attB region on the chromosome,
and

(RV in
pUC119) and

(in the
ccrB gene) flanking the
attSCC
region on the plasmids (Fig.
4). The
results showed that the plasmid
pSRatt generated
plasmid-chromosome junctions which were detectable
only by the
two combinations of the primers, L-

and R-

. On the
other hand,
the plasmid-chromosome junctions generated by pSRtta
were detected only
by the combinations of the primers, L-

and
R-

. Integration in the
opposite orientation could not be detected
with the sensitivity of PCR
employed in this study: the PCR sensitivity
was such that it was
able to detect the integrated template in
N315ex(pSRatt) DNA
diluted up to 10
4 times (wt/wt) with N315ex(pYT3att)
DNA (data not
shown).
The amplified DNAs from N315ex(pSRatt) and from
N315ex(pSRtta) contained sequences which were identical with
those of the
chromosome-SCC
mec junction regions
(
attL and
attR) of N315 as
presented in Fig.
1A.
PCR with any combinations of the primers did not amplify DNA fragments
on template DNAs extracted from any of the transformants
[N315ex(pYT3), N315ex(pSRA*att), N315ex(pSRB*att), or
N315ex(pSR)
(not shown)]. This showed that all of
ccrA,
ccrB, and
attSCC were
required for the
integration of the experimental
plasmids.
 |
DISCUSSION |
The size of SCCmec (52 kb) is comparable to
those of other genetic elements such as bacteriophages, conjugative
transposons, and pathogenicity islands, but SCCmec
does not have any structural similarity to those previously identified
genetic elements: it is distinguishable from conjugative transposons
since it lacks the tra gene complex (5), and from
bacteriophages because it lacks the structure genes (or their remnants)
for head or tail proteins of bacteriophages (29).
Unlike SCCmec pathogenicity islands
(18, 19), does not contain any ORFs predictably encoding virulence factors as far as we could judge from the homology search of
extant gene products (14). Besides these structural
characteristics of SCCmec, we demonstrated, in
this study, that SCCmec carries a set of unique
recombinase genes, ccrA and ccrB, that are
specifically involved in the recombination events (integration and
excision) of SCCmec with the S. aureus
chromosome. The presence of the two genes was required for both
excision and integration processes of SCCmec. In
other genetic elements, such as bacteriophage lambda and conjugative
transposons, two site-specific recombinases, designated integrase and
excisionase, are reported to be required for the excision process.
However, in these elements, the integration can be mediated by the
integrase alone (5, 29).
The Ccr recombinases are also characteristic in that their
NH2-terminal thirds had a substantial homology to the
recombinases of the invertase/resolvase family, whereas the integrases
of bacteriophage lambda and conjugative transposons belong to the
integrase family of site-specific recombinases. The characteristic
serine residue that is considered to offer the hydroxyl group that
attacks the DNA molecule in the strand exchange reaction is conserved
among the recombinases of the invertase/resolvase family and in Ccr proteins as well, but Ccr proteins also differ considerably from the
recombinases of the invertase/resolvase family in that they possess
much larger COOH-terminal domains than those possessed by the
recombinases belonging to this family. A homology search of the
COOH-terminal domains did not find any homologue in the extant
proteins. Therefore, the molecular evolutionary relationship of Ccr
proteins to other recombinases and their mode of action pose intriguing
questions to be explored.
Since the 1960s, the spontaneous loss of the mecA gene has
been observed during the storage or long-term cultivation of MRSA strains in antibiotic-free medium (11). Deletion of a large chromosomal region is identified in such mecA deletion
strains. The deletion starts precisely from the left boundary of
IS431mec and extends leftwards for various distances beyond
the mecA gene. The precise excision of
SCCmec demonstrated in this study is unrelated to
the transposase-mediated mecA deletions (14).
Curiously, spontaneous precise excision does not occur appreciably
during cultivation of N315 despite the fact that the strain carries an intact pair of ccr genes on its chromosome. The excision
does, however, seem to occur at an extremely low frequency and can be detected by nested-PCR amplification of the attB sequence
(14). Therefore, it is an intriguing question whether
the expression of the intact copy of ccr genes of
SCCmec is down regulated to stabilize the
SCCmec in the chromosome. Alternatively,
even an unrestricted expression of a single copy of the
ccr genes on the chromosome may not be enough to increase
the concentration of Ccr proteins to a level high enough to
trigger the excision of SCCmec. A study
is under way to clarify these points.
It is well known that the mecA gene is carried by many
staphylococcal species besides S. aureus (13,
28), so it has been suspected that mecA is
transmissible among staphylococcal species. In fact, methicillin
resistance can be experimentally transferred between S. aureus cells by phage transduction (6). The DNA element
with similar structural features to SCCmec is also
identified in the strains of various staphylococcal species with the
methicillin resistance phenotype (T. Ito, unpublished observation).
Thus, it seems that the methicillin resistance gene mecA is
transferred from cell to cell as a part of the
SCCmec across staphylococcal species. However, as
far as we are aware, no transducing phage capable of transferring
genetic information across the staphylococcal species barrier has been
described. Thus, it remains to be seen if SCCmec
is transmissible by phage transduction or if some other genetic
transfer system specific for the movement of
SCCmec exists.
In conclusion, we have demonstrated that the methicillin resistance
gene of MRSA is carried by a novel genetic element,
SCCmec, whose integration into and excision from
the S. aureus chromosome are mediated by a unique set of
recombinase genes, ccrA and ccrB. Further study
of the distribution of SCCmec and its related
elements among S. aureus and other staphylococcal species
will be helpful to elucidate how staphylococcal species exchange
useful genetic information. Also, future elucidation of the
mechanism of regulation of SCCmec excision may
lead to the attractive possibility of the development of a novel
therapeutic measure to aid in antibiotic chemotherapy against MRSA
infection by converting MRSA strains in vivo into MSSA strains against
which many extant antibiotics are effective.
 |
ACKNOWLEDGMENTS |
We thank K. Tsutsumimoto for her excellent technical assistance
and Yasmin Abu Hanifah for valuable suggestions concerning the
worldwide epidemiology of MRSA.
This work was supported by the Core University Program under the
auspices of the Japan Society for the Promotion of Science (JSPS),
coordinated by the Graduate School of Medicine, University of Tokyo,
and School of Medical Sciences, Universiti Sains Malaysia, and by the
Specially Designated Research Promotion of Monbusho, Japan.
 |
FOOTNOTES |
*
Corresponding author. Mailing address: Department of
Bacteriology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, Japan 113-8421. Phone: 81-3-5802-1040. Fax: 81-3-5684-7830. E-mail: hiram{at}med.juntendo.ac.jp.
 |
REFERENCES |
| 1.
|
Ayliffe, G. A.
1997.
The progressive intercontinental spread of methicillin-resistant Staphylococcus aureus.
Clin. Infect. Dis.
24(Suppl. 1):74-79.
|
| 2.
|
Barberis-Maino, L.,
B. Berger-Bachi,
H. Weber,
W. D. Beck, and F. H. Kayser.
1987.
IS431, a staphylococcal insertion sequence-like element related to IS26 from Proteus vulgaris.
Gene
59:107-113[CrossRef][Medline].
|
| 3.
|
Chambers, H. F., and H. C. Neu.
1995.
Penicillins, p. 233-246.
In
G. Mandell, J. E. Bennett, and R. Dolin (ed.), Principles and practice of infectious diseases. Churchill Livingstone, New York, N.Y.
|
| 4.
|
Christiansen, B.,
L. Brondsted,
F. K. Vogensen, and K. Hammer.
1996.
A resolvase-like protein is required for the site-specific integration of the temperate lactococcal bacteriophage TP901-1.
J. Bacteriol.
178:5164-5173[Abstract/Free Full Text].
|
| 5.
|
Clewell, D. B.
1998.
Conjugative transposons, p. 130-139.
In
F. J. de Bruijn, J. R. Lupski, and G. M. Weinstock (ed.), Bacterial genomes. Chapman and Hall, New York, N.Y.
|
| 6.
|
Cohen, S., and H. M. Sweeney.
1970.
Transduction of methicillin resistance in Staphylococcus aureus dependent on an unusual specificity of the recipient strain.
J. Bacteriol.
104:1158-1167[Abstract/Free Full Text].
|
| 7.
|
Dubin, D. T.,
P. R. Matthews,
S. G. Chikramane, and P. R. Stewart.
1991.
Physical mapping of the mec region of an American methicillin-resistant Staphylococcus aureus strain.
Antimicrob. Agents Chemother.
35:1661-1665[Abstract/Free Full Text].
|
| 8.
|
Hanaki, H.,
K. Kuwahara-Arai,
S. Boyle-Vavra,
R. S. Daum,
H. Labischinski, and K. Hiramatsu.
1998.
Activated cell-wall synthesis is associated with vancomycin resistance in methicillin-resistant Staphylococcus aureus clinical strains Mu3 and Mu50.
J. Antimicrob. Chemother.
42:199-209[Abstract/Free Full Text].
|
| 9.
|
Hartman, B. J., and A. Tomasz.
1984.
Low-affinity penicillin-binding protein associated with beta-lactam resistance in Staphylococcus aureus.
J. Bacteriol.
158:513-516[Abstract/Free Full Text].
|
| 10.
|
Hiramatsu, K.,
K. Asada,
E. Suzuki,
K. Okonogi, and T. Yokota.
1992.
Molecular cloning and nucleotide sequence determination of the regulator region of mecA gene in methicillin-resistant Staphylococcus aureus (MRSA).
FEBS Lett.
298:133-136[CrossRef][Medline].
|
| 11.
|
Hiramatsu, K.,
E. Suzuki,
H. Takayama,
Y. Katayama, and T. Yokota.
1990.
Role of penicillinase plasmids in the stability of the mecA gene in methicillin-resistant Staphylococcus aureus.
Antimicrob. Agents Chemother.
34:600-604[Abstract/Free Full Text].
|
| 12.
|
Hiramatsu, K.,
T. Ito, and H. Hanaki.
1999.
Evolution of methicillin and glycopeptide resistance in Staphylococcus aureus, p. 221-242.
In
R. G. Finch, and R. J. Williams (ed.), Bailliere's clinical infectious disease. Bailliere Tindall, London, United Kingdom.
|
| 13.
|
Hurlimann-Dalei, R. L.,
C. Ryffel,
F. H. Kayser, and B. Berger-Bachi.
1992.
Survey of the methicillin resistance-associated genes mecA, mecR1-mecI, and femA-femB in clinical isolates of methicillin-resistant Staphylococcus aureus.
Antimicrob. Agents Chemother.
36:2617-2621[Abstract/Free Full Text].
|
| 14.
|
Ito, T.,
Y. Katayama, and K. Hiramatsu.
1999.
Cloning and nucleotide sequence determination of the entire mec DNA of pre-methicillin-resistant Staphylococcus aureus N315.
Antimicrob. Agents Chemother.
43:1449-1458[Abstract/Free Full Text].
|
| 15.
|
Jevons, M. P.
1961.
"Celbenin"-resistant staphylococci.
Br. Med. J.
1:124-125.
|
| 16.
|
Kreiswirth, B.,
J. Kornblum,
R. D. Arbeit,
W. Eisner,
J. N. Maslow,
A. McGeer,
D. E. Low, and P. R. Novick.
1993.
Evidence for a clonal origin of methicillin resistance in Staphylococcus aureus.
Science
259:227-230[Abstract/Free Full Text].
|
| 17.
|
Kuwahara-Arai, K.,
N. Kondo-Hori,
E. Tateda-Suzuki, and K. Hiramatsu.
1996.
Suppression of methicillin resistance in a mecA-containing pre-methicillin-resistant Staphylococcus aureus strain is caused by the mecI-mediated repression of PBP2' production.
Antimicrob. Agents Chemother.
40:2680-2685[Abstract].
|
| 18.
|
Lee, C. A.
1996.
Pathogenicity islands and the evolution of bacterial pathogens.
Infect. Agents Dis.
5:1-7[Medline].
|
| 19.
|
Lindsay, J. A.,
A. Ruzin,
H. F. Ross,
N. Kurepina, and R. P. Novick.
1998.
The gene for toxic shock toxin is carried by a family of mobile pathogenicity islands in Staphylococcus aureus.
Mol. Microbiol.
29:527-543[CrossRef][Medline].
|
| 20.
|
Matsuhashi, M.,
M. D. Song,
F. Ishino,
M. Wachi,
M. Doi,
M. Inoue,
K. Ubukata,
N. Yamashita, and M. Konno.
1986.
Molecular cloning of the gene of a penicillin binding protein supposed to cause high resistance to beta-lactam antibiotics in Staphylococcus aureus.
J. Bacteriol.
167:975-980[Abstract/Free Full Text].
|
| 21.
|
Matthews, P., and A. Tomasz.
1990.
Insertional inactivation of the mec gene in a transposon mutant of a methicillin-resistant clinical isolate of Staphylococcus aureus.
Antimicrob. Agents Chemother.
34:1777-1779[Abstract/Free Full Text].
|
| 22.
|
McKenzie, H. T.,
T. Hoshino,
T. Tanaka, and N. Sueoka.
1986.
The nucleotide sequence of pUB110: some salient features in relation to replication and its regulation.
Plasmid
15:93-103[CrossRef][Medline].
|
| 23.
|
Murphy,
E. L. Huwyler, and M. C. Bastos.
1985.
Transposon Tn554: complete nucleotide sequence and isolation of transposition-defective and antibiotic-sensitive mutants.
EMBO J.
4:3357-3365[Medline].
|
| 24.
|
Reynolds, P. E., and D. F. J. Brown.
1985.
Penicillin-binding proteins of beta-lactam-resistant strains of Staphylococcus aureus.
FEBS Lett.
192:28-32[CrossRef][Medline].
|
| 25.
|
Sherratt, D.
1989.
Tn3 and related transposable elements: site-specific recombination and transposition, p. 163-184.
In
D. E. Berg, and M. M. Howe (ed.), Mobile DNA. American Society for Microbiology, Washington, D.C.
|
| 26.
|
Song, M. D.,
M. Wachi,
M. Doi,
F. Ishino, and M. Matsuhashi.
1987.
Evolution of an inducible penicillin-target protein in methicillin-resistant Staphylococcus aureus by gene fusion.
FEBS Lett.
221:167-171[CrossRef][Medline].
|
| 27.
|
Stewart, P. R.,
D. T. Dubin,
S. G. Chikramane,
B. Ingli,
P. R. Matthews, and S. M. Poston.
1994.
IS257 and small plasmid insertions in the mec region of the chromosome of Staphylococcus aureus.
Plasmid
31:12-20[CrossRef][Medline].
|
| 28.
|
Suzuki, E.,
K. Hiramatsu, and T. Yokota.
1992.
Survey of methicillin-resistant clinical strains of coagulase-negative staphylococci for mecA gene distribution.
Antimicrob. Agents Chemother.
36:429-434[Abstract/Free Full Text].
|
| 29.
|
Thompson, J. F., and A. Landy.
1989.
Regulation of bacteriophage lambda site-specific recombination, p. 1-22.
In
D. E. Berg, and M. M. Howe (ed.), Mobile DNA. American Society for Microbiology, Washington, D.C.
|
| 30.
|
Utsui, Y., and T. Yokota.
1985.
Role of an altered penicillin-binding protein in methicillin- and cephem-resistant Staphylococcus aureus.
Antimicrob. Agents Chemother.
28:397-403[Abstract/Free Full Text].
|
| 31.
|
Wada, A.,
Y. Katayama,
K. Hiramatsu, and T. Yokota.
1991.
Southern hybridization analysis of the mecA deletion from methicillin-resistant Staphylococcus aureus.
Biochem. Biophys. Res. Commun.
176:1319-1325[CrossRef][Medline].
|
| 32.
|
Yoshida, T.,
N. Kondo,
Y. A. Hanifah, and K. Hiramatsu.
1997.
Combined use of ribotyping, PFGE typing and IS431 typing the discrimination of nosocomical strains of methicillin-resistant Staphylococcus aureus.
Microbiol. Immunol.
41:687-695[Medline].
|
Antimicrobial Agents and Chemotherapy, June 2000, p. 1549-1555, Vol. 44, No. 6
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
-
International Working Group on the Classification,
(2009). Classification of Staphylococcal Cassette Chromosome mec (SCCmec): Guidelines for Reporting Novel SCCmec Elements. Antimicrob. Agents Chemother.
53: 4961-4967
[Full Text]
-
Pantosti, A., Venditti, M.
(2009). What is MRSA?. Eur Respir J
34: 1190-1196
[Abstract]
[Full Text]
-
Chen, L., Mediavilla, J. R., Oliveira, D. C., Willey, B. M., de Lencastre, H., Kreiswirth, B. N.
(2009). Multiplex Real-Time PCR for Rapid Staphylococcal Cassette Chromosome mec Typing. J. Clin. Microbiol.
47: 3692-3706
[Abstract]
[Full Text]
-
Llarrull, L. I., Fisher, J. F., Mobashery, S.
(2009). Molecular Basis and Phenotype of Methicillin Resistance in Staphylococcus aureus and Insights into New {beta}-Lactams That Meet the Challenge. Antimicrob. Agents Chemother.
53: 4051-4063
[Full Text]
-
Argudin, M. A., Mendoza, M. C., Mendez, F. J., Martin, M. C., Guerra, B., Rodicio, M. R.
(2009). Clonal Complexes and Diversity of Exotoxin Gene Profiles in Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus Isolates from Patients in a Spanish Hospital. J. Clin. Microbiol.
47: 2097-2105
[Abstract]
[Full Text]
-
Pi, B., Yu, M., Chen, Y., Yu, Y., Li, L.
(2009). Distribution of the ACME-arcA gene among meticillin-resistant Staphylococcus haemolyticus and identification of a novel ccr allotype in ACME-arcA-positive isolates. J Med Microbiol
58: 731-736
[Abstract]
[Full Text]
-
Mulvey, M. R. PhD, Simor, A. E. MD
(2009). Antimicrobial resistance in hospitals: How concerned should we be?. CMAJ
180: 408-415
[Full Text]
-
Ruppe, E., Barbier, F., Mesli, Y., Maiga, A., Cojocaru, R., Benkhalfat, M., Benchouk, S., Hassaine, H., Maiga, I., Diallo, A., Koumare, A. K., Ouattara, K., Soumare, S., Dufourcq, J.-B., Nareth, C., Sarthou, J.-L., Andremont, A., Ruimy, R.
(2009). Diversity of Staphylococcal Cassette Chromosome mec Structures in Methicillin-Resistant Staphylococcus epidermidis and Staphylococcus haemolyticus Strains among Outpatients from Four Countries. Antimicrob. Agents Chemother.
53: 442-449
[Abstract]
[Full Text]
-
Ibrahem, S., Salmenlinna, S., Virolainen, A., Kerttula, A.-M., Lyytikainen, O., Jagerroos, H., Broas, M., Vuopio-Varkila, J.
(2009). Carriage of Methicillin-Resistant Staphylococci and Their SCCmec Types in a Long-Term-Care Facility. J. Clin. Microbiol.
47: 32-37
[Abstract]
[Full Text]
-
Berglund, C., Ito, T., Ikeda, M., Ma, X. X., Soderquist, B., Hiramatsu, K.
(2008). Novel Type of Staphylococcal Cassette Chromosome mec in a Methicillin-Resistant Staphylococcus aureus Strain Isolated in Sweden. Antimicrob. Agents Chemother.
52: 3512-3516
[Abstract]
[Full Text]
-
Nakaminami, H., Noguchi, N., Ikeda, M., Hasui, M., Sato, M., Yamamoto, S., Yoshida, T., Asano, T., Senoue, M., Sasatsu, M.
(2008). Molecular epidemiology and antimicrobial susceptibilities of 273 exfoliative toxin-encoding-gene-positive Staphylococcus aureus isolates from patients with impetigo in Japan. J Med Microbiol
57: 1251-1258
[Abstract]
[Full Text]
-
Hu, D.-L., Omoe, K., Inoue, F., Kasai, T., Yasujima, M., Shinagawa, K., Nakane, A.
(2008). Comparative prevalence of superantigenic toxin genes in meticillin-resistant and meticillin-susceptible Staphylococcus aureus isolates. J Med Microbiol
57: 1106-1112
[Abstract]
[Full Text]
-
Noto, M. J., Fox, P. M., Archer, G. L.
(2008). Spontaneous Deletion of the Methicillin Resistance Determinant, mecA, Partially Compensates for the Fitness Cost Associated with High-Level Vancomycin Resistance in Staphylococcus aureus. Antimicrob. Agents Chemother.
52: 1221-1229
[Abstract]
[Full Text]
-
Noto, M. J., Kreiswirth, B. N., Monk, A. B., Archer, G. L.
(2008). Gene Acquisition at the Insertion Site for SCCmec, the Genomic Island Conferring Methicillin Resistance in Staphylococcus aureus. J. Bacteriol.
190: 1276-1283
[Abstract]
[Full Text]
-
Sieradzki, K., Chung, M., Tomasz, A.
(2008). Role of a Sodium-Dependent Symporter Homologue in the Thermosensitivity of {beta}-Lactam Antibiotic Resistance and Cell Wall Composition in Staphylococcus aureus. Antimicrob. Agents Chemother.
52: 505-512
[Abstract]
[Full Text]
-
Zhou, Y., Antignac, A., Wu, S. W., Tomasz, A.
(2008). Penicillin-Binding Proteins and Cell Wall Composition in -Lactam-Sensitive and -Resistant Strains of Staphylococcus sciuri. J. Bacteriol.
190: 508-514
[Abstract]
[Full Text]
-
Miragaia, M., Carrico, J. A., Thomas, J. C., Couto, I., Enright, M. C., de Lencastre, H.
(2008). Comparison of Molecular Typing Methods for Characterization of Staphylococcus epidermidis: Proposal for Clone Definition. J. Clin. Microbiol.
46: 118-129
[Abstract]
[Full Text]
-
Donnio, P.-Y., Fevrier, F., Bifani, P., Dehem, M., Kervegant, C., Wilhelm, N., Gautier-Lerestif, A.-L., Lafforgue, N., Cormier, M., the MR-MSSA Study Group of the College de Bacterio, , Le Coustumier, A.
(2007). Molecular and Epidemiological Evidence for Spread of Multiresistant Methicillin-Susceptible Staphylococcus aureus Strains in Hospitals. Antimicrob. Agents Chemother.
51: 4342-4350
[Abstract]
[Full Text]
-
Park, C., Lee, D.-G., Kim, S. W., Choi, S.-M., Park, S. H., Chun, H.-S., Choi, J.-H., Yoo, J.-H., Shin, W. S., Kang, J. H., Kim, J. H., Lee, S. Y., Kim, S. M., Pyun, B. Y.
(2007). Predominance of Community-Associated Methicillin-Resistant Staphylococcus aureus Strains Carrying Staphylococcal Chromosome Cassette mec Type IVA in South Korea. J. Clin. Microbiol.
45: 4021-4026
[Abstract]
[Full Text]
-
Mombach Pinheiro Machado, A. B., Reiter, K. C., Paiva, R. M., Barth, A. L.
(2007). Distribution of staphylococcal cassette chromosome mec (SCCmec) types I, II, III and IV in coagulase-negative staphylococci from patients attending a tertiary hospital in southern Brazil. J Med Microbiol
56: 1328-1333
[Abstract]
[Full Text]
-
Milheirico, C., Oliveira, D. C., de Lencastre, H.
(2007). Update to the Multiplex PCR Strategy for Assignment of mec Element Types in Staphylococcus aureus. Antimicrob. Agents Chemother.
51: 3374-3377
[Abstract]
[Full Text]
-
Goff, D. A., Dowzicky, M. J.
(2007). Prevalence and regional variation in meticillin-resistant Staphylococcus aureus (MRSA) in the USA and comparative in vitro activity of tigecycline, a glycylcycline antimicrobial. J Med Microbiol
56: 1189-1193
[Abstract]
[Full Text]
-
Stephens, A. J., Huygens, F., Giffard, P. M.
(2007). Systematic Derivation of Marker Sets for Staphylococcal Cassette Chromosome mec Typing. Antimicrob. Agents Chemother.
51: 2954-2964
[Abstract]
[Full Text]
-
Maiques, E., Ubeda, C., Tormo, M. A., Ferrer, M. D., Lasa, I., Novick, R. P., Penades, J. R.
(2007). Role of Staphylococcal Phage and SaPI Integrase in Intra- and Interspecies SaPI Transfer. J. Bacteriol.
189: 5608-5616
[Abstract]
[Full Text]
-
Milheirico, C., Oliveira, D. C., de Lencastre, H.
(2007). Multiplex PCR strategy for subtyping the staphylococcal cassette chromosome mec type IV in methicillin-resistant Staphylococcus aureus: 'SCCmec IV multiplex'. J Antimicrob Chemother
60: 42-48
[Abstract]
[Full Text]
-
Hanssen, A.-M., Sollid, J. U. E.
(2007). Multiple Staphylococcal Cassette Chromosomes and Allelic Variants of Cassette Chromosome Recombinases in Staphylococcus aureus and Coagulase-Negative Staphylococci from Norway. Antimicrob. Agents Chemother.
51: 1671-1677
[Abstract]
[Full Text]
-
Pereira, S. F. F., Henriques, A. O., Pinho, M. G., de Lencastre, H., Tomasz, A.
(2007). Role of PBP1 in Cell Division of Staphylococcus aureus. J. Bacteriol.
189: 3525-3531
[Abstract]
[Full Text]
-
Miragaia, M., Thomas, J. C., Couto, I., Enright, M. C., de Lencastre, H.
(2007). Inferring a Population Structure for Staphylococcus epidermidis from Multilocus Sequence Typing Data. J. Bacteriol.
189: 2540-2552
[Abstract]
[Full Text]
-
Ghebremedhin, B., Konig, W., Witte, W., Hardy, K. J., Hawkey, P. M., Konig, B.
(2007). Subtyping of ST22-MRSA-IV (Barnim epidemic MRSA strain) at a university clinic in Germany from 2002 to 2005. J Med Microbiol
56: 365-375
[Abstract]
[Full Text]
-
Kondo, Y., Ito, T., Ma, X. X., Watanabe, S., Kreiswirth, B. N., Etienne, J., Hiramatsu, K.
(2007). Combination of Multiplex PCRs for Staphylococcal Cassette Chromosome mec Type Assignment: Rapid Identification System for mec, ccr, and Major Differences in Junkyard Regions. Antimicrob. Agents Chemother.
51: 264-274
[Abstract]
[Full Text]
-
Heusser, R., Ender, M., Berger-Bachi, B., McCallum, N.
(2007). Mosaic Staphylococcal Cassette Chromosome mec Containing Two Recombinase Loci and a New mec Complex, B2. Antimicrob. Agents Chemother.
51: 390-393
[Abstract]
[Full Text]
-
Ma, X. X., Ito, T., Chongtrakool, P., Hiramatsu, K.
(2006). Predominance of Clones Carrying Panton-Valentine Leukocidin Genes among Methicillin-Resistant Staphylococcus aureus Strains Isolated in Japanese Hospitals from 1979 to 1985. J. Clin. Microbiol.
44: 4515-4527
[Abstract]
[Full Text]
-
Kilic, A., Li, H., Stratton, C. W., Tang, Y.-W.
(2006). Antimicrobial Susceptibility Patterns and Staphylococcal Cassette Chromosome mec Types of, as Well as Panton-Valentine Leukocidin Occurrence among, Methicillin-Resistant Staphylococcus aureus Isolates from Children and Adults in Middle Tennessee. J. Clin. Microbiol.
44: 4436-4440
[Abstract]
[Full Text]
-
Oliveira, D. C., Milheirico, C., de Lencastre, H.
(2006). Redefining a Structural Variant of Staphylococcal Cassette Chromosome mec, SCCmec Type VI.. Antimicrob. Agents Chemother.
50: 3457-3459
[Abstract]
[Full Text]
-
Noto, M. J., Archer, G. L.
(2006). A Subset of Staphylococcus aureus Strains Harboring Staphylococcal Cassette Chromosome mec (SCCmec) Type IV Is Deficient in CcrAB-Mediated SCCmec Excision.. Antimicrob. Agents Chemother.
50: 2782-2788
[Abstract]
[Full Text]
-
Jansen, W. T. M., Beitsma, M. M., Koeman, C. J., van Wamel, W. J. B., Verhoef, J., Fluit, A. C.
(2006). Novel Mobile Variants of Staphylococcal Cassette Chromosome mec in Staphylococcus aureus.. Antimicrob. Agents Chemother.
50: 2072-2078
[Abstract]
[Full Text]
-
Noguchi, N., Nakaminami, H., Nishijima, S., Kurokawa, I., So, H., Sasatsu, M.
(2006). Antimicrobial Agent of Susceptibilities and Antiseptic Resistance Gene Distribution among Methicillin-Resistant Staphylococcus aureus Isolates from Patients with Impetigo and Staphylococcal Scalded Skin Syndrome.. J. Clin. Microbiol.
44: 2119-2125
[Abstract]
[Full Text]
-
Layer, F., Ghebremedhin, B., Konig, W., Konig, B.
(2006). Heterogeneity of Methicillin-Susceptible Staphylococcus aureus Strains at a German University Hospital Implicates the Circulating-Strain Pool as a Potential Source of Emerging Methicillin-Resistant S. aureus Clones.. J. Clin. Microbiol.
44: 2179-2185
[Abstract]
[Full Text]
-
Tsuru, T., Kawai, M., Mizutani-Ui, Y., Uchiyama, I., Kobayashi, I.
(2006). Evolution of Paralogous Genes: Reconstruction of Genome Rearrangements Through Comparison of Multiple Genomes Within Staphylococcus aureus. Mol Biol Evol
23: 1269-1285
[Abstract]
[Full Text]
-
Vivoni, A. M., Diep, B. A., de Gouveia Magalhaes, A. C., Santos, K. R. N., Riley, L. W., Sensabaugh, G. F., Moreira, B. M.
(2006). Clonal Composition of Staphylococcus aureus Isolates at a Brazilian University Hospital: Identification of International Circulating Lineages.. J. Clin. Microbiol.
44: 1686-1691
[Abstract]
[Full Text]
-
Chongtrakool, P., Ito, T., Ma, X. X., Kondo, Y., Trakulsomboon, S., Tiensasitorn, C., Jamklang, M., Chavalit, T., Song, J.-H., Hiramatsu, K.
(2006). Staphylococcal Cassette Chromosome mec (SCCmec) Typing of Methicillin-Resistant Staphylococcus aureus Strains Isolated in 11 Asian Countries: a Proposal for a New Nomenclature for SCCmec Elements. Antimicrob. Agents Chemother.
50: 1001-1012
[Abstract]
[Full Text]
-
Malik, S., Peng, H., Barton, M. D.
(2006). Partial Nucleotide Sequencing of the mecA Genes of Staphylococcus aureus Isolates from Cats and Dogs. J. Clin. Microbiol.
44: 413-416
[Abstract]
[Full Text]
-
Yang, J. A., Park, D. W., Sohn, J. W., Kim, M. J.
(2006). Novel PCR-Restriction Fragment Length Polymorphism Analysis for Rapid Typing of Staphylococcal Cassette Chromosome mec Elements. J. Clin. Microbiol.
44: 236-238
[Abstract]
[Full Text]
-
Stephens, A. J., Huygens, F., Inman-Bamber, J., Price, E. P., Nimmo, G. R., Schooneveldt, J., Munckhof, W., Giffard, P. M.
(2006). Methicillin-resistant Staphylococcus aureus genotyping using a small set of polymorphisms. J Med Microbiol
55: 43-51
[Abstract]
[Full Text]
-
O'Brien, F. G., Coombs, G. W., Pearson, J. C., Christiansen, K. J., Grubb, W. B.
(2005). Type V Staphylococcal Cassette Chromosome mec in Community Staphylococci from Australia. Antimicrob. Agents Chemother.
49: 5129-5132
[Abstract]
[Full Text]
-
Rihn, J. A., Michaels, M. G., Harner, C. D.
(2005). Community-Acquired Methicillin-Resistant Staphylococcus aureus: An Emerging Problem in the Athletic Population. Am J Sports Med
33: 1924-1929
[Abstract]
[Full Text]
-
Kwon, N. H., Park, K. T., Moon, J. S., Jung, W. K., Kim, S. H., Kim, J. M., Hong, S. K., Koo, H. C., Joo, Y. S., Park, Y. H.
(2005). Staphylococcal cassette chromosome mec (SCCmec) characterization and molecular analysis for methicillin-resistant Staphylococcus aureus and novel SCCmec subtype IVg isolated from bovine milk in Korea. J Antimicrob Chemother
56: 624-632
[Abstract]
[Full Text]
-
Kowalski, T. J., Berbari, E. F., Osmon, D. R.
(2005). Epidemiology, Treatment, and Prevention of Community-Acquired Methicillin-Resistant Staphylococcus aureus Infections. Mayo Clin Proc.
80: 1201-1208
[Abstract]
-
Donnio, P.-Y., Oliveira, D. C., Faria, N. A., Wilhelm, N., Le Coustumier, A., de Lencastre, H.
(2005). Partial Excision of the Chromosomal Cassette Containing the Methicillin Resistance Determinant Results in Methicillin-Susceptible Staphylococcus aureus. J. Clin. Microbiol.
43: 4191-4193
[Abstract]
[Full Text]
-
Hisata, K., Kuwahara-Arai, K., Yamanoto, M., Ito, T., Nakatomi, Y., Cui, L., Baba, T., Terasawa, M., Sotozono, C., Kinoshita, S., Yamashiro, Y., Hiramatsu, K.
(2005). Dissemination of Methicillin-Resistant Staphylococci among Healthy Japanese Children. J. Clin. Microbiol.
43: 3364-3372
[Abstract]
[Full Text]
-
Trindade, P. d. A., Pacheco, R. L., Costa, S. F., Rossi, F., Barone, A. A., Mamizuka, E. M., Levin, A. S.
(2005). Prevalence of SCCmec Type IV in Nosocomial Bloodstream Isolates of Methicillin-Resistant Staphylococcus aureus. J. Clin. Microbiol.
43: 3435-3437
[Abstract]
[Full Text]
-
O'Brien, F. G., Lim, T. T., Winnett, D. C., Coombs, G. W., Pearson, J. C., Delgado, A., Langevin, M. J., Cantore, S. A., Gonzalez, L., Gustafson, J. E.
(2005). Survey of Methicillin-Resistant Staphylococcus aureus Strains from Two Hospitals in El Paso, Texas. J. Clin. Microbiol.
43: 2969-2972
[Abstract]
[Full Text]
-
Shore, A., Rossney, A. S., Keane, C. T., Enright, M. C., Coleman, D. C.
(2005). Seven Novel Variants of the Staphylococcal Chromosomal Cassette mec in Methicillin-Resistant Staphylococcus aureus Isolates from Ireland. Antimicrob. Agents Chemother.
49: 2070-2083
[Abstract]
[Full Text]
-
Hanssen, A.-M., Fossum, A., Mikalsen, J., Halvorsen, D. S., Bukholm, G., Sollid, J. U. E.
(2005). Dissemination of Community-Acquired Methicillin-Resistant Staphylococcus aureus Clones in Northern Norway: Sequence Types 8 and 80 Predominate. J. Clin. Microbiol.
43: 2118-2124
[Abstract]
[Full Text]
-
Katayama, Y., Robinson, D. A., Enright, M. C., Chambers, H. F.
(2005). Genetic Background Affects Stability of mecA in Staphylococcus aureus. J. Clin. Microbiol.
43: 2380-2383
[Abstract]
[Full Text]
-
Zhang, H., Morikawa, K., Ohta, T., Kato, Y.
(2005). In vitro resistance to the CS{alpha}{beta}-type antimicrobial peptide ASABF- is conferred by overexpression of sigma factor sigB in Staphylococcus aureus. J Antimicrob Chemother
55: 686-691
[Abstract]
[Full Text]
-
Gill, S. R., Fouts, D. E., Archer, G. L., Mongodin, E. F., DeBoy, R. T., Ravel, J., Paulsen, I. T., Kolonay, J. F., Brinkac, L., Beanan, M., Dodson, R. J., Daugherty, S. C., Madupu, R., Angiuoli, S. V., Durkin, A. S., Haft, D. H., Vamathevan, J., Khouri, H., Utterback, T., Lee, C., Dimitrov, G., Jiang, L., Qin, H., Weidman, J., Tran, K., Kang, K., Hance, I. R., Nelson, K. E., Fraser, C. M.
(2005). Insights on Evolution of Virulence and Resistance from the Complete Genome Analysis of an Early Methicillin-Resistant Staphylococcus aureus Strain and a Biofilm-Producing Methicillin-Resistant Staphylococcus epidermidis Strain. J. Bacteriol.
187: 2426-2438
[Abstract]
[Full Text]
-
Ribeiro, A., Dias, C., Silva-Carvalho, M. C., Berquo, L., Ferreira, F. A., Santos, R. N. S., Ferreira-Carvalho, B. T., Figueiredo, A. M.
(2005). First Report of Infection with Community-Acquired Methicillin-Resistant Staphylococcus aureus in South America. J. Clin. Microbiol.
43: 1985-1988
[Abstract]
[Full Text]
-
van Griethuysen, A., van Loo, I., van Belkum, A., Vandenbroucke-Grauls, C., Wannet, W., van Keulen, P., Kluytmans, J.
(2005). Loss of the mecA Gene during Storage of Methicillin-Resistant Staphylococcus aureus Strains. J. Clin. Microbiol.
43: 1361-1365
[Abstract]
[Full Text]
-
Kazakova, S. V., Hageman, J. C., Matava, M., Srinivasan, A., Phelan, L., Garfinkel, B., Boo, T., McAllister, S., Anderson, J., Jensen, B., Dodson, D., Lonsway, D., McDougal, L. K., Arduino, M., Fraser, V. J., Killgore, G., Tenover, F. C., Cody, S., Jernigan, D. B.
(2005). A Clone of Methicillin-Resistant Staphylococcus aureus among Professional Football Players. NEJM
352: 468-475
[Abstract]
[Full Text]
-
Shelburne, S. A., Musher, D. M., Hulten, K., Ceasar, H., Lu, M. Y., Bhaila, I., Hamill, R. J.
(2004). In Vitro Killing of Community-Associated Methicillin-Resistant Staphylococcus aureus with Drug Combinations. Antimicrob. Agents Chemother.
48: 4016-4019
[Abstract]
[Full Text]
-
Ito, T., Ma, X. X., Takeuchi, F., Okuma, K., Yuzawa, H., Hiramatsu, K.
(2004). Novel Type V Staphylococcal Cassette Chromosome mec Driven by a Novel Cassette Chromosome Recombinase, ccrC. Antimicrob. Agents Chemother.
48: 2637-2651
[Abstract]
[Full Text]
-
Holden, M. T. G., Feil, E. J., Lindsay, J. A., Peacock, S. J., Day, N. P. J., Enright, M. C., Foster, T. J., Moore, C. E., Hurst, L., Atkin, R., Barron, A., Bason, N., Bentley, S. D., Chillingworth, C., Chillingworth, T., Churcher, C., Clark, L., Corton, C., Cronin, A., Doggett, J., Dowd, L., Feltwell, T., Hance, Z., Harris, B., Hauser, H., Holroyd, S., Jagels, K., James, K. D., Lennard, N., Line, A., Mayes, R., Moule, S., Mungall, K., Ormond, D., Quail, M. A., Rabbinowitsch, E., Rutherford, K., Sanders, M., Sharp, S., Simmonds, M., Stevens, K., Whitehead, S., Barrell, B. G., Spratt, B. G., Parkhill, J.
(2004). Complete genomes of two clinical Staphylococcus aureus strains: Evidence for the rapid evolution of virulence and drug resistance. Proc. Natl. Acad. Sci. USA
101: 9786-9791
[Abstract]
[Full Text]
-
Ender, M., McCallum, N., Adhikari, R., Berger-Bachi, B.
(2004). Fitness Cost of SCCmec and Methicillin Resistance Levels in Staphylococcus aureus. Antimicrob. Agents Chemother.
48: 2295-2297
[Abstract]
[Full Text]
-
Oteo, J., Baquero, F., Vindel, A., Campos, J., on behalf of the Spanish members of The European A,
(2004). Antibiotic resistance in 3113 blood isolates of Staphylococcus aureus in 40 Spanish hospitals participating in the European Antimicrobial Resistance Surveillance System (2000-2002). J Antimicrob Chemother
53: 1033-1038
[Abstract]
[Full Text]
-
Mongkolrattanothai, K., Boyle, S., Murphy, T. V., Daum, R. S.
(2004). Novel Non-mecA-Containing Staphylococcal Chromosomal Cassette Composite Island Containing pbp4 and tagF Genes in a Commensal Staphylococcal Species: a Possible Reservoir for Antibiotic Resistance Islands in Staphylococcus aureus. Antimicrob. Agents Chemother.
48: 1823-1836
[Abstract]
[Full Text]
-
Huletsky, A., Giroux, R., Rossbach, V., Gagnon, M., Vaillancourt, M., Bernier, M., Gagnon, F., Truchon, K., Bastien, M., Picard, F. J., van Belkum, A., Ouellette, M., Roy, P. H., Bergeron, M. G.
(2004). New Real-Time PCR Assay for Rapid Detection of Methicillin- Resistant Staphylococcus aureus Directly from Specimens Containing a Mixture of Staphylococci. J. Clin. Microbiol.
42: 1875-1884
[Abstract]
[Full Text]
-
Huygens, F., Stephens, A. J., Nimmo, G. R., Giffard, P. M.
(2004). mecA Locus Diversity in Methicillin-Resistant Staphylococcus aureus Isolates in Brisbane, Australia, and the Development of a Novel Diagnostic Procedure for the Western Samoan Phage Pattern Clone. J. Clin. Microbiol.
42: 1947-1955
[Abstract]
[Full Text]
-
Katayama, Y., Zhang, H.-Z., Chambers, H. F.
(2004). PBP 2a Mutations Producing Very-High-Level Resistance to Beta-Lactams. Antimicrob. Agents Chemother.
48: 453-459
[Abstract]
[Full Text]
-
Schmidt, H., Hensel, M.
(2004). Pathogenicity Islands in Bacterial Pathogenesis. Clin. Microbiol. Rev.
17: 14-56
[Abstract]
[Full Text]
-
Hanssen, A.-M., Kjeldsen, G., Sollid, J. U. E.
(2004). Local Variants of Staphylococcal Cassette Chromosome mec in Sporadic Methicillin-Resistant Staphylococcus aureus and Methicillin-Resistant Coagulase-Negative Staphylococci: Evidence of Horizontal Gene Transfer?. Antimicrob. Agents Chemother.
48: 285-296
[Abstract]
[Full Text]
-
Hardy, K. J., Hawkey, P. M., Gao, F., Oppenheim, B. A.
(2004). Methicillin resistant Staphylococcus aureus in the critically ill. Br J Anaesth
92: 121-130
[Abstract]
[Full Text]
-
Robinson, D. A., Enright, M. C.
(2003). Evolutionary Models of the Emergence of Methicillin-Resistant Staphylococcus aureus. Antimicrob. Agents Chemother.
47: 3926-3934
[Abstract]
[Full Text]
-
Garcia-Castellanos, R., Marrero, A., Mallorqui-Fernandez, G., Potempa, J., Coll, M., Gomis-Ruth, F. X.
(2003). Three-dimensional Structure of MecI: MOLECULAR BASIS FOR TRANSCRIPTIONAL REGULATION OF STAPHYLOCOCCAL METHICILLIN RESISTANCE. J. Biol. Chem.
278: 39897-39905
[Abstract]
[Full Text]
-
Katayama, Y., Zhang, H.-Z., Hong, D., Chambers, H. F.
(2003). Jumping the Barrier to {beta}-Lactam Resistance in Staphylococcus aureus. J. Bacteriol.
185: 5465-5472
[Abstract]
[Full Text]
-
Katayama, Y., Takeuchi, F., Ito, T., Ma, X. X., Ui-Mizutani, Y., Kobayashi, I., Hiramatsu, K.
(2003). Identification in Methicillin-Susceptible Staphylococcus hominis of an Active Primordial Mobile Genetic Element for the Staphylococcal Cassette Chromosome mec of Methicillin-Resistant Staphylococcus aureus. J. Bacteriol.
185: 2711-2722
[Abstract]
[Full Text]
-
Rohrer, S., Berger-Bachi, B.
(2003). FemABX Peptidyl Transferases: a Link between Branched-Chain Cell Wall Peptide Formation and {beta}-Lactam Resistance in Gram-Positive Cocci. Antimicrob. Agents Chemother.
47: 837-846
[Full Text]
-
Boyle-Vavra, S., Yin, S., Challapalli, M., Daum, R. S.
(2003). Transcriptional Induction of the Penicillin-Binding Protein 2 Gene in Staphylococcus aureus by Cell Wall-Active Antibiotics Oxacillin and Vancomycin. Antimicrob. Agents Chemother.
47: 1028-1036
[Abstract]
[Full Text]
-
Reipert, A., Ehlert, K., Kast, T., Bierbaum, G.
(2003). Morphological and Genetic Differences in Two Isogenic Staphylococcus aureus Strains with Decreased Susceptibilities to Vancomycin. Antimicrob. Agents Chemother.
47: 568-576
[Abstract]
[Full Text]
-
Yoshida, R., Kuwahara-Arai, K., Baba, T., Cui, L., Richardson, J. F., Hiramatsu, K.
(2003). Physiological and molecular analysis of a mecA-negative Staphylococcus aureus clinical strain that expresses heterogeneous methicillin resistance. J Antimicrob Chemother
51: 247-255
[Abstract]
[Full Text]
-
Okuma, K., Iwakawa, K., Turnidge, J. D., Grubb, W. B., Bell, J. M., O'Brien, F. G., Coombs, G. W., Pearman, J. W., Tenover, F. C., Kapi, M., Tiensasitorn, C., Ito, T., Hiramatsu, K.
(2002). Dissemination of New Methicillin-Resistant Staphylococcus aureus Clones in the Community. J. Clin. Microbiol.
40: 4289-4294
[Abstract]
[Full Text]
-
Oliveira, D. C., Lencastre, H. d.
(2002). Multiplex PCR Strategy for Rapid Identification of Structural Types and Variants of the mec Element in Methicillin-Resistant Staphylococcus aureus. Antimicrob. Agents Chemother.
46: 2155-2161
[Abstract]
[Full Text]
-
Luong, T. T., Ouyang, S., Bush, K., Lee, C. Y.
(2002). Type 1 Capsule Genes of Staphylococcus aureus Are Carried in a Staphylococcal Cassette Chromosome Genetic Element. J. Bacteriol.
184: 3623-3629
[Abstract]
[Full Text]
-
MOORE, P.C. L., LINDSAY, J.A.
(2002). Molecular characterisation of the dominant UK methicillin-resistant Staphylococcus aureus strains, EMRSA-15 and EMRSA-16. J Med Microbiol
51: 516-521
[Abstract]
[Full Text]
-
Ma, X. X., Ito, T., Tiensasitorn, C., Jamklang, M., Chongtrakool, P., Boyle-Vavra, S., Daum, R. S., Hiramatsu, K.
(2002). Novel Type of Staphylococcal Cassette Chromosome mec Identified in Community-Acquired Methicillin-Resistant Staphylococcus aureus Strains. Antimicrob. Agents Chemother.
46: 1147-1152
[Abstract]
[Full Text]
-
Donnio, P.-Y., Louvet, L., Preney, L., Nicolas, D., Avril, J.-L., Desbordes, L.
(2002). Nine-Year Surveillance of Methicillin-Resistant Staphylococcus aureus in a Hospital Suggests Instability of mecA DNA Region in an Epidemic Strain. J. Clin. Microbiol.
40: 1048-1052
[Abstract]
[Full Text]
-
Katayama, Y., Ito, T., Hiramatsu, K.
(2001). Genetic Organization of the Chromosome Region Surrounding mecA in Clinical Staphylococcal Strains: Role of IS431-Mediated mecI Deletion in Expression of Resistance in mecA-Carrying, Low-Level Methicillin- Resistant Staphylococcus haemolyticus. Antimicrob. Agents Chemother.
45: 1955-1963
[Abstract]
[Full Text]
-
Aires de Sousa, M., Miragaia, M., Santos Sanches, I., Avila, S., Adamson, I., Casagrande, S. T., Brandileone, M. C. C., Palacio, R., Dell'Acqua, L., Hortal, M., Camou, T., Rossi, A., Velazquez-Meza, M. E., Echaniz-Aviles, G., Solorzano-Santos, F., Heitmann, I., de Lencastre, H.
(2001). Three-Year Assessment of Methicillin-Resistant Staphylococcus aureus Clones in Latin America from 1996 to 1998. J. Clin. Microbiol.
39: 2197-2205
[Abstract]
[Full Text]
-
Ito, T., Katayama, Y., Asada, K., Mori, N., Tsutsumimoto, K., Tiensasitorn, C., Hiramatsu, K.
(2001). Structural Comparison of Three Types of Staphylococcal Cassette Chromosome mec Integrated in the Chromosome in Methicillin-Resistant Staphylococcus aureus. Antimicrob. Agents Chemother.
45: 1323-1336
[Abstract]
[Full Text]
-
Kondo, N., Kuwahara-Arai, K., Kuroda-Murakami, H., Tateda-Suzuki, E., Hiramatsu, K.
(2001). Eagle-Type Methicillin Resistance: New Phenotype of High Methicillin Resistance under mec Regulator Gene Control. Antimicrob. Agents Chemother.
45: 815-824
[Abstract]
[Full Text]
-
Mundy, L. M., Sahm, D. F., Gilmore, M.
(2000). Relationships between Enterococcal Virulence and Antimicrobial Resistance. Clin. Microbiol. Rev.
13: 513-522
[Abstract]
[Full Text]