Previous Article | Next Article 
Antimicrobial Agents and Chemotherapy, January 2001, p. 117-123, Vol. 45, No. 1
0066-4804/01/$04.00+0 DOI: 10.1128/AAC.45.1.117-123.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Molecular Basis of High-Level Ciprofloxacin
Resistance in Neisseria gonorrhoeae Strains Isolated in
Denmark from 1995 to 1998
Xiaohong
Su
and
Inga
Lind*
Neisseria Unit, Department of Respiratory
Infections, Meningitis and STIs, Statens Serum Institut,
Copenhagen, Denmark
Received 14 April 2000/Returned for modification 12 July
2000/Accepted 3 October 2000
 |
ABSTRACT |
In Denmark surveillance of the in vitro susceptibility to
ciprofloxacin of Neisseria gonorrhoeae was established in
1990. The proportion of N. gonorrhoeae strains with
decreased susceptibility or resistance to ciprofloxacin (MIC 
0.06 µg/ml) was low (0.3 to 2.3%) up to 1995. Between 1995 and 1998 the rate of less-susceptible and resistant strains rose from 6.9 to
13.2%. Among ciprofloxacin-resistant strains (MIC 1 µg/ml),
81% were highly resistant (MIC 4 µg/ml). Thirty-five
N. gonorrhoeae strains (40 isolates) for which
ciprofloxacin MICs were 4 to 32 µg/ml were investigated for the
frequency and patterns of mutations within the gyrA and
parC genes. The quinolone resistance-determining regions of
the gyrA and parC genes were amplified by PCR,
and the amplicons were directly sequenced. Alterations at Ser-91 and
Asp-95 in GyrA and a single or double alteration in ParC were
identified in 32 strains (91%). Ser-91-to-Phe and Asp-95-to-Gly
alterations in GyrA were detected in 28 strains (80%). The most common
ParC alteration, Asp-86 to Asn, was found in 19 strains (54%). The
strains were analyzed for genetic relationship by pulsed-field gel
electrophoresis (PFGE). The analysis showed that nine strains with the
same mutation pattern in the gyrA and parC
genes, originating from different geographical areas over 3 years, had
the same PFGE patterns after SpeI as well as
NheI digestion (only one strain with one band difference in
the NheI pattern), suggesting that a resistant clone had
spread worldwide. The results from this study strongly suggest that
double gyrA mutations plus a parC
mutation(s) play an important role in the development of
high-level fluoroquinolone resistance in N. gonorrhoeae.
| |
INTRODUCTION |
After the emergence and worldwide
spread of penicillin- and tetracycline-resistant Neisseria
gonorrhoeae strains, fluoroquinolones have been recommended as
primary therapy for uncomplicated gonorrhea in many countries
(31). Over the past 10 years, N. gonorrhoeae strains with decreased susceptibility or resistance to fluoroquinolones have been found in several countries, particularly in southeast Asia
and western Pacific areas (7, 10, 12, 13, 25, 30). An
N. gonorrhoeae strain with high-level ciprofloxacin resistance was reported for the first time in 1994 (2).
During recent years the rate of gonorrhea has fallen dramatically in Denmark. Simultaneously, the proportion of multiresistant gonococci has
risen sharply (15). Surveillance of susceptibility to
ciprofloxacin in N. gonorrhoeae was initiated in 1990. The
proportion of strains showing reduced susceptibility or resistance to
ciprofloxacin (MIC 0.06 µg/ml) was low (0.3 to 2.3%) up to
1995. Two gonococcal isolates resistant to ciprofloxacin (0.3% of the
isolates tested; MIC, 1 µg/ml) were found in 1992. Resistant strains
were not detected between 1993 and 1994. However, since 1995 the
numbers of N. gonorrhoeae strains with decreased
susceptibility or resistance to ciprofloxacin have risen markedly.
To analyze quinolone resistance mechanisms in N. gonorrhoeae
a number of studies of laboratory mutant strains (1, 4) and clinical isolates (22-24, 29) were performed. The
resistance to fluoroquinolones was shown primarily to be associated
with mutations in the gyrA gene, coding for DNA gyrase, and
in the parC gene, coding for DNA topoisomerase IV (1,
4, 22, 23, 28), and less often with reduced uptake and
accumulation of fluoroquinolone in the cells (21). The
level of fluoroquinolone resistance appears to correlate to the
location and number of mutations in gyrA and
parC. Among the strains examined so far only a few strains
exhibited high-level resistance to fluoroquinolone. In this paper, we
report the occurrence of fluoroquinolone resistance among N. gonorrhoeae strains isolated in Denmark from 1995 to 1998 and the
frequency and patterns of mutations involving gyrA and
parC genes in 35 strains (40 isolates) highly resistant to ciprofloxacin. We also examined the genetic relationship of the 40 isolates by pulsed-field gel electrophoresis (PFGE).
| |
MATERIALS AND METHODS |
Bacterial strains.
From 1995 to 1998 a total of 809 culture-confirmed cases of gonorrhea occurred in Denmark. The methods
used for primary isolation and identification of gonococci were the
same as those described previously (20). All strains were
sent to the National Reference Laboratory for antimicrobial
susceptibility testing. In total 40 clinical isolates of N. gonorrhoeae for which ciprofloxacin MICs ranged from 4 to 32 µg/ml were available for the study. Information about the origin of
the strains investigated was available from the request form sent to
the reference laboratory or from the attending physician, who is
obliged to obtain information about country of exposure according to
the compulsory notification system for communicable diseases.
Antimicrobial susceptibility testing.
Penicillinase
production was demonstrated by means of the chromogenic cephalosporin
test (18). All strains were examined for susceptibility to
ciprofloxacin, penicillin, tetracycline, and ceftriaxone by the agar
plate dilution method using Danish chocolate agar medium
(17). The antibiotic concentrations (twofold dilution
steps) used were as follows: ciprofloxacin, 0.001 to 32 µg/ml;
penicillin, 0.016 to 4.0 µg/ml; tetracycline, 0.125 to 64 µg/ml (32 µg/ml in 1995); ceftriaxone, 0.001 to 0.25 µg/ml. Strains for which
the MICs of ciprofloxacin were 0.03 µg/ml or less, 0.06 to 0.5 µg/ml, and 1 µg/ml or more were designated susceptible, less
susceptible, and resistant, respectively (25).
Plasmid analysis.
The plasmid profiles of
penicillinase-producing N. gonorrhoeae (PPNG) strains were
analyzed as described previously (20).
Determination of changes in gyrA and parC
genes.
PCR and direct DNA sequencing of the amplicons were
performed to identify mutations within the gyrA and
parC genes. PCR primers specific for genes corresponding to
the quinolone resistance-determining regions within GyrA and ParC were
the same as those used by Tanaka et al. (22, 23) and
described by Belland et al. (1). The DNA sequences were
determined in both directions by using the ABI PRISM dye terminator
cycle sequencing ready reaction kit (Perkin-Elmer, Applied Biosystems,
Foster City, Calif.) and an ABI 377A automated DNA sequencer and
analyzed by using Sequence Navigator software (Perkin-Elmer, Applied Biosystems).
PFGE analysis.
Genomic DNA was prepared as described
previously (3). Slices of DNA-containing agarose blocks
were digested with SpeI and NheI (New England
Biolabs) overnight at 37°C in 100 µl of restriction endonuclease
buffer containing 10 U of enzyme. Digested blocks were electrophoresed
in a 1% agarose gel in a contour-clamped homogeneous electric field
(CHEF DR III) system (Bio-Rad). Running conditions were 22 h at
12°C at a voltage of 6 V/cm with pulse times of 1 to 40 s.
The gels were stained with ethidium bromide, destained in distilled
water, and photographed under UV transillumination. Subsequently, the
patterns were scanned using a scientific imaging system (Digital Science ID; Eastman Kodak Company, Rochester, N.Y.). PFGE fingerprints were analyzed with GelCompar software (version 4.1; Applied Maths, Kortrijk, Belgium). The similarity of the PFGE banding patterns was
estimated with the Dice coefficient and the unweighted pair group
method using arithmetic averages. A tolerance in the band positions of
1.0% and an optimization setting of 0.5% were used. Bands smaller
than 5 kb were not included in the analysis of the NheI
pattern. A 90% similarity threshold was used to divide the outputs
from the dendrograms into clusters.
| |
RESULTS |
Susceptibility to ciprofloxacin.
In Denmark the first strains
displaying high-level quinolone resistance (MIC 4 µg/ml)
appeared in 1995. From 1995 to 1998 the percentage of strains
exhibiting decreased susceptibility to ciprofloxacin increased from 2.9 to 7.1% and the percentage of ciprofloxacin-resistant strains rose
from 3.9 to 6.1% (Table 1). The MIC at
which 90% of isolates were inhibited increased from 0.016 to 0.128 µg/ml. Among the 42 resistant strains isolated during the period, the
MICs for 7 strains were 1 or 2 µg/ml and those for 35 (83%) were
between 4 and 32 µg/ml.
Study population.
Table 2
summarizes data on the phenotypes and origin of 40 highly resistant
N. gonorrhoeae isolates from 35 patients. From five patients
pairs of isolates were available, of which four had been obtained
before and after treatment with ciprofloxacin. For all five pairs the
second isolate exhibited the same phenotypic features as the first one.
Hence, only 35 strains were available for the comparative analyses.
Among these strains, 23 were PPNG and 12 were non-PPNG. All the
isolates were susceptible to ceftriaxone. Tetracycline-resistant
strains were common, but none was suspected of carrying the
tetM determinant (MIC 
8 µg/ml). Of the 35 patients, 24 had been infected abroad, primarily in east Asia. Of the
four who had acquired their infection in Denmark, three had contacts with patients infected abroad. For seven patients the country of
acquisition was unknown. Among 27 strains isolated from 1995 to 1997 21 were PPNG (78%), while only 1 of 8 was PPNG in 1998 (13%).
Plasmid analysis.
All the 23 PPNG strains included in the
study contained the 4.2-kb cryptic plasmid as well as the 38.9-kb
conjugative plasmid except one strain which did not contain the 38.9-kb
plasmid; 17 out of 23 PPNG strains carried the 4.9-kb Toronto plasmid,
four carried the 7.2-kb Asian plasmid, and two carried the 5.1-kb
African plasmid. Thus four different plasmid profiles were represented among the strains: 17 strains contained the 4.2-, 4.9-, and 38.9-kb plasmids, 3 carried the 4.2-, 7.2-, and 38.9-kb plasmids, 2 carried the
4.2-, 5.1-, and 38.9-kb plasmids, and 1 carried only the 4.2- and
7.2-kb plasmids.
Mutation patterns in the gyrA and parC
genes.
Table 3 shows the mutation
patterns found in gyrA and parC genes in 35 high-level quinolone-resistant strains. We identified multiple
mutations in gyrA and parC genes among these
strains. All strains except one had double mutations at codons 91 and
95 in the gyrA gene with a single, double, or triple
mutation(s) in the parC gene. One strain (24/97) contained
only a single mutation at codon 91 in the gyrA gene.
Among the GyrA alterations identified, Ser-91 to Phe (Ser-91 of
N. gonorrhoeae GyrA corresponds to Ser-83 of
Escherichia coli GyrA [
1]) was the most
common, having been identified in 34
of the 35 gonococcal strains
(97%); a Ser-91-to-Tyr alteration
was detected in one strain (41/97).
An Asp-95-to-Gly alteration
(Asp-95 of
N. gonorrhoeae GyrA
corresponds to Asp-87 of
E. coli GyrA [
1])
was found in 30 strains (86%). An Asp-95-to-Asn alteration
was
identified in four strains (11%). An Asp-95-to-Ala alteration
which
has not been described previously, was found in one strain
(56/98). The
double GyrA alteration of Ser-91 to Phe and Asp-95
to Gly was detected
in 28 of the 35 strains (80%).
Sequence analysis of the
parC gene demonstrated a variety of
mutations at codons 86, 87, 88, 91, 104, and 131. The most common
ParC
alteration, Asp-86 to Asn (Asp-86 of
N. gonorrhoeae
ParC
corresponds to Asp-79 of
E. coli ParC
[
1]), was found in 19
strains (54%). A silent mutation
in the DNA sequence from CTC
to CTG at codon 131 was also identified in
19 strains (54%). A
Glu-91-to-Lys alteration was found in 10 strains
(29%), a Ser-87-to-Asn
alteration was found in 9 strains (26%), a
Ser-88-to-Pro alteration
was found in 2 strains (6%), a Ser-87-to-Arg
alteration was found
in 1 strain (3%), and a silent mutation at codon
104 (Tyr) was
found in one strain (3%).
Combination of
gyrA mutations and
parC mutations
gave 13 different mutation patterns among the 35 strains (Table
3). The
alterations of Ser-91 to Phe and Asp-95 to Gly in GyrA and Asp-86
to
Asn in ParC were found in 14 strains (40%). Some mutation patterns
have not been observed previously. There was no difference between
the
first and the second isolates within pairs or between isolates
from sex
partners either in antimicrobial susceptibility or in
the mutation
patterns of
gyrA and
parC genes.
PFGE analysis.
Genomic DNA from all 40 isolates of N. gonorrhoeae was examined by PFGE after treatment with
endonucleases SpeI and NheI. The PFGE profiles
obtained after SpeI digestion showed 12 to 17 DNA fragments
ranging in size from approximately 23 to 540 kb. The PFGE profiles
identified by NheI digestion showed 12 to 19 DNA fragments
ranging from approximately 20 to 650 kb.
The Dice coefficient and a 90% similarity threshold gave 12 different
SpeI profiles and 15
NheI profiles among the 40 isolates
(Fig.
1 and
2). Out of eight
strains, each of which had a unique
pattern of mutations in the
gyrA and
parC genes, seven also had
unique
SpeI and
NheI
patterns, indicating that these strains
were
genetically unrelated. Among the 11 strains with the most common
mutation pattern (M9), 9 (76/95, 181/95, 80/96, 72/96, 137/97,
163/97,
165/97, 167/97, 176/97) were classified into one cluster
with identical
SpeI patterns (Fig.
3) as well
as
NheI patterns
(Fig.
4)
except for one strain (76/95) that had one band difference
from the
other strains: the addition of a large DNA fragment of
approximately
540 kb in the
SpeI pattern. These nine strains were
all PPNG
carrying the 4.9-kb Toronto type plasmid but originated
from various
places over 3 years. Of the eight strains with the
second-most-common
mutation pattern (M11), six were classified
into the same cluster on
the basis of the
SpeI patterns or
NheI
patterns
at 96 and 90% similarity thresholds, respectively. Five
strains
contained the 4.9-kb Toronto type plasmid, and one harbored
the 5.1-kb
African type plasmid. Among these six strains, five
originated from
Thailand and one originated from Iraq.
View larger version (80K):
[in this window]
[in a new window]
|
FIG. 3.
PFGE analysis of genomic DNAs from N. gonorrhoeae strains digested with SpeI. Lanes 1, 7, 13, and 19, lambda DNA ladder; lanes 2 to 6, 8 to 12, and 14 to 18, strains
182/98, 183/98, 193/98, 194/98, 56/98, 63/98, 76/95, 181/95, 72/96,
80/96, 137/97, 163/97, 165/97, 167/97, and 176/97, respectively. (See
Table 2 for epidemiologic data.) The DNA preparation of strain 182/98
was tested before and gave the same pattern as that for 183/98, 193/98,
and 194/98 (data not shown).
|
|
View larger version (83K):
[in this window]
[in a new window]
|
FIG. 4.
PFGE analysis of genomic DNAs from N. gonorrhoeae strains digested with NheI. Lanes 1, 7, 13, and 19, lambda DNA ladder; lanes 2 to 6, 8 to 12, and 14 to 18, strains
56/98, 88/98, 86/95, 21/97, 66/96, 81/95, 76/95, 181/95, 72/96, 80/96,
137/97, 163/97, 165/97, 167/97, and 176/97, respectively. (See Table 2
for epidemiologic data.)
|
|
Pairs of isolates recovered from the same patients (Fig.
5) and strains from sexual partners (Fig.
3 and
4) showed the same
PFGE patterns after
SpeI and
NheI digestion. One pair of isolates
(121/95 and 128/95) had
the same
SpeI pattern but differed in
NheI
pattern: that of the posttreatment isolate (128/95) lacked
two small
bands of approximately 250 and 40 kb found in that of
121/95 and had a
large band of approximately 290 kb not found
in that of 121/95 (Fig.
5).
View larger version (85K):
[in this window]
[in a new window]
|
FIG. 5.
PFGE analysis of genomic DNAs from N. gonorrhoeae strains digested with SpeI and
NheI. Lanes 1, 11, and 20, lambda DNA ladder; lanes 2 to 10 and 12 to 13 (after SpeI digestion), strains 80/96, 88/96,
121/95, 128/95, 160/95, 165/95, 31/95, 253/95, 109/96, 134/97, and
105/98, respectively; lanes 14 to 19 (after NheI digestion),
strains 80/96, 88/96, 121/95, 128/95, 160/95, and 165/95, respectively.
(See Table 2 for epidemiologic data.)
|
|
| |
DISCUSSION |
Fluoroquinolones act by inhibiting the topoisomerase enzymes
essential for DNA replication and recombination. Fluoroquinolone resistance in bacteria has been associated with alterations in the GyrA
subunit of DNA gyrase (type II topoisomerase) and in the ParC subunit
of DNA topoisomerase IV and with the reduction of drug accumulation in
the cells. The development of high-level fluoroquinolone resistance
occurs through stepwise mutations (6). Studies on
laboratory mutants and clinical isolates of N. gonorrhoeae have revealed that gyrA mutation plays an important role in
the development of fluoroquinolone resistance and that simultaneous parC and gyrA mutation plays a complementary role
in increasing the level of resistance (1, 4, 28). The
reduced fluoroquinolone accumulation in the bacteria is thought to have
an additional but lesser effect (21). Previous studies
have revealed that gonococcal isolates fully susceptible to
ciprofloxacin had no alterations in GyrA and ParC or had a single
alteration in GyrA alone (24); strains exhibiting
decreased susceptibility (MICs, 0.125 to 0.5 µg/ml) generally
contained alterations only in GyrA (4, 10). When a ParC
alteration was detected in a less-susceptible strain, only a single
GyrA alteration was present (29). Ciprofloxacin-resistant strains (MICs, 1 µg/ml), with few exceptions, had GyrA alterations at positions 91 and 95 and at least one ParC alteration (4, 28,
29).
In this study we demonstrated that 91% of strains for which
ciprofloxacin MICs were 4 to 32 µg/ml and which were isolated between
1995 and 1998 contained the double GyrA alteration at the 91 and 95 positions and a single or double ParC alteration(s). Our results
strongly suggest that the double gyrA mutation plus parC mutation play an important role in the development of
high-level resistance to fluoroquinolone in N. gonorrhoeae.
There was no significant correlation between the number of mutations in
the parC gene and the susceptibility to ciprofloxacin.
Strains with the same mutation pattern for parC but with
different levels of ciprofloxacin resistance (MICs, 8 to 64 µg/ml)
have been found previously (28).
In our study 63% of the high-level ciprofloxacin-resistant strains
were PPNG. A high proportion of PPNG strains among quinolone-resistant strains was also reported by Tapsall et al. (26).
Interestingly, the majority of the PPNG strains (83%) contained the
4.9-kb Toronto type plasmid. All the PPNG strains containing the 4.9-kb
plasmid also contained the 38.9-kb conjugative plasmid, which is in
agreement with previous studies (14, 20). A shift from
predominantly PPNG strains to non-PPNG strains among the
ciprofloxacin-resistant strains was observed in 1998.
A wide variety of phenotypes of quinolone-resistant N. gonorrhoeae strains with decreased susceptibilities to
fluoroquinolones have been reported in Hong Kong and Japan (5,
11). A single strain or closely related strains of N. gonorrhoeae have been demonstrated to be associated with a focal
area of endemic transmission in Cleveland, Ohio, (12) and
Ontario, Canada (9). Among quinolone-resistant N. gonorrhoeae strains a shift from multiple subtypes being imported to a limited number of subtypes sustained domestically was documented in Australia (26), and the spread of quinolone-resistant
strains has been assumed to be due in part at least to the presence of these phenotypes in international commercial sex workers and their clients (26). An increasing proportion of N. gonorrhoeae strains highly resistant to ciprofloxacin (MIC, 4 µg/ml) was observed among female sex workers in the Philippines from
1994 to 1997 (13). In Denmark infections with
quinolone-resistant strains were most often acquired abroad or through
contact with persons infected abroad (16). Although few in
number, they made up a high proportion of all cases. According to the
country-wide laboratory surveillance system, endemic spread of
gonorrhea was infrequent from 1995 onwards (16).
PFGE is often considered the "gold standard" of molecular typing
methods (19) and has been applied successfully to a wide range of bacterial species, both gram positive and gram negative (27). In this study the most interesting observation
documented by PFGE is the identification of a cluster of nine strains
originating from different places (Philippines, Hong Kong, Rumania, New
Guinea, and Denmark) over 3 years, which suggests that a common
epidemic clone may be widely spread. They also had identical patterns
of mutations in the gyrA and parC genes, which
also substantiated the assumption that they were genetically related.
Close genetic relationships between strains of N. gonorrhoeae recovered from distinct locations separated by
thousands of miles over a 2-year period have already been demonstrated
by Xia et al. (32). No differences in the gyrA
and parC mutation patterns or in susceptibility to
ciprofloxacin between pretreatment and posttreatment isolates from the
same patients or between sexual partners were observed. Pairs of
isolates from sexual partners had indistinguishable SpeI and
NheI patterns, confirming that they were isogenic and
epidemiologically related. An interesting point was the one band
difference in PFGE pattern between two isolates (121/95 and 128/95)
from the same patient. On the basis of the criteria defined by Tenover
et al. (27), a single genetic event such as a point
mutation in the posttreatment isolate could be reflected as a
difference of one to three bands. PFGE pattern variation between the
posttreatment isolate and the original isolate was previously reported
by Harnett et al. (8). In their report the interval
between the recovery of the two isolates was 4 months. The interval was
short in our patient, only 5 days.
In conclusion, the observations described in this study showed that the
increase in the number of ciprofloxacin-resistant isolates of N. gonorrhoeae in Denmark was due to the importation of resistant
strains from abroad, that a resistant bacterial clone which might have
originated in east Asia seems to have spread worldwide, and that double
alterations at Ser-91 and Asp-95 in GyrA plus a single or double ParC
alteration(s) play an important role in the development of high-level
fluoroquinolone resistance in N. gonorrhoeae.
| |
ACKNOWLEDGMENT |
We gratefully acknowledge the staff of the Clinical Biochemistry
Department, Statens Serum Institut, for technical assistance with the sequencing.
| |
FOOTNOTES |
*
Corresponding author. Mailing address: Neisseria Unit,
Department of Respiratory Infections, Meningitis and STIs, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen S, Denmark. Phone: (45)
3268 3475. Fax: (45) 32683142. E-mail: il{at}ssi.dk.
Present address: Department of STD, National Center for STD and
Leprosy Control, Institute of Dermatology, Chinese Academy of Medical
Sciences, Nanjing 210042, People's Republic of China.
| |
REFERENCES |
| 1.
|
Belland, R. J.,
S. G. Morrison,
C. A. Ison, and W. M. Huang.
1994.
Neisseria gonorrhoeae acquires mutations in analogous regions of gyrA and parC in fluoroquinolone resistant isolates.
Mol. Microbiol.
14:371-380[Medline].
|
| 2.
|
Birley, H.,
P. McDonald, and P. Carey.
1994.
High level ciprofloxacin resistance in Neisseria gonorrhoeae.
Genitourin. Med.
70:292-293[Medline].
|
| 3.
|
Bygraves, J. A., and M. C. J. Maiden.
1992.
Analysis of the clonal relationships between strains of Neisseria meningitidis by pulsed field gel electrophoresis.
J. Gen. Microbiol.
138:523-531[Abstract/Free Full Text].
|
| 4.
|
Deguchi, T.,
M. Yasuda,
M. Nakano,
S. Ozeki,
T. Ezaki,
I. Saito, and Y. Kawada.
1996.
Quinolone-resistant Neisseria gonorrhoeae; correlation of alterations in the GyrA subunit of DNA gyrase and the ParC subunit of topoisomerase IV with antimicrobial susceptibility profiles.
Antimicrob. Agents Chemother.
40:1020-1023[Abstract].
|
| 5.
|
Deguchi, T.,
M. Yasuda,
S. I. Maeda,
I. Saito, and Y. Kawada.
1998.
Serotyping of quinolone-resistant Neisseria gonorrhoeae isolates with alterations in GyrA and ParC.
J. Antimicrob. Chemother.
41:418-420[Free Full Text].
|
| 6.
|
Fisher, L. M.
1998.
New insights into mechanisms of quinolone action and resistance.
Mol. Biol. Genet.
15(Suppl. E):55-60.
|
| 7.
|
Fox, K. K.,
J. S. Knapp,
K. K. Holmes,
E. W. Hook III,
F. N. Judson,
S. E. Thompson,
J. A. Washington, and W. L. Whittington.
1997.
Antimicrobial resistance in Neisseria gonorrhoeae in the United States, 1988-1994: the emergence of decreased susceptibility to the fluoroquinolones.
J. Infect. Dis.
175:1396-1403[Medline].
|
| 8.
|
Harnett, N.,
S. Brown,
R. Terro,
C. Krishnan,
M. Pauze, and K.-H. Yeung.
1997.
High-level tetracycline-resistant Neisseria gonorrhoeae in Ontario, Canada investigation of a cluster of isolates, showing chromosomally mediated resistance to penicillin combined with plasmid-mediated resistance to tetracycline.
J. Infect. Dis.
176:1269-1276[Medline].
|
| 9.
|
Harnett, N.,
S. Brown,
G. Riley,
R. Terro,
C. Krishnan,
M. Pauze, and K.-H. Yeung.
1997.
Analysis of Neisseria gonorrhoeae in Ontario, Canada, with decreased susceptibility to quinolones by pulse-field gel electrophoresis, auxotyping, serotyping and plasmid content.
J. Med. Microbiol.
46:383-390[Abstract/Free Full Text].
|
| 10.
|
Ison, C. A.,
P. J. Woodford,
H. Madders, and E. Claydon.
1998.
Drift in susceptibility of Neisseria gonorrhoeae to ciprofloxacin and emergence of therapeutic failure.
Antimicrob. Agents Chemother.
42:2919-2922[Abstract/Free Full Text].
|
| 11.
|
Kam, K. M.,
P. W. Wong,
M. M. Cheung,
N. K. Y. Ho, and K. K. Lo.
1996.
Quinolone-resistant Neisseria gonorrhoeae in Hong Kong.
Sex. Transm. Dis.
23:103-108[Medline].
|
| 12.
|
Kilmarx, P. H.,
J. S. Knapp,
M. Xia,
M. E. St. Louis,
S. W. Neal,
D. Sayers,
L. J. Doyle,
M. C. Roberts, and W. L. Whittington.
1998.
Intercity spread of gonococci with decreased susceptibility to fluoroquinolones: a unique focus in the United States.
J. Infect. Dis.
177:677-682[Medline].
|
| 13.
|
Klausner, J. D.,
M.-R. Aplasca,
V. P. Mesola,
G. Bolan,
W. L. Whittington, and K. K. Holmes.
1999.
Correlates of gonococcal infection and antimicrobial-resistant Neisseria gonorrhoeae among female sex workers, Republic of the Philippines, 1996-1997.
J. Infect. Dis.
179:729-733[CrossRef][Medline].
|
| 14.
|
Knapp, J. S.,
V. P. Mesola,
S. W. Neal,
T. E. Wi,
C. Tuazon,
R. Manalastas,
P. L. Perine, and W. L. Whittington.
1997.
Molecular epidemiology, in 1994, of Neisseria gonorrhoeae in Manila and Cebu City, Republic of the Philippines.
Sex. Transm. Dis.
24:2-7[Medline].
|
| 15.
|
Lind, I.
1997.
Antimicrobial resistance in Neisseria gonorrhoeae.
Clin. Infect. Dis.
24(Suppl. 1):S93-S97.
|
| 16.
|
Lind, I., and E. Smith.
1998.
Gonorrhoea 1997.
EPI News Denmark
49:1.
|
| 17.
|
Lind, I.
1996.
Gonorrhoea.
Curr. Probl. Dermatol. (Basel)
24:12-19.
|
| 18.
|
O'Callaghan, C. H.,
A. Morris,
S. M. Kirby, and A. H. Shingler.
1972.
Novel method for detection of  -lactamases by using a chromogenic cephalosporin substrate.
Antimicrob. Agents Chemother.
1:283-288[Abstract/Free Full Text].
|
| 19.
|
Olive, D. M., and P. Bean.
1999.
Principles and applications of methods for DNA-based typing of microbial organisms.
J. Clin. Microbiol.
37:1661-1669[Free Full Text].
|
| 20.
|
Reimann, K.,
A. C. Bollerup, and I. Lind.
1992.
The emergence of penicillinase-producing Neisseria gonorrhoeae strains carrying the 4.9 kb (Toronto) plasmid in Denmark and of a novel large plasmid in two nonpenicillinase-producing Neisseria gonorrhoeae strains.
Sex. Transm. Dis.
19:206-212[Medline].
|
| 21.
|
Tanaka, M.,
S. Sakuma,
K. Takahashi,
T. Nagahuzi,
T. Saika,
I. Kobayashi, and J. Kumazawa.
1998.
Analysis of quinolone resistance mechanisms in Neisseria gonorrhoeae isolates in vitro.
Sex. Transm. Infect.
74:59-62[Abstract].
|
| 22.
|
Tanaka, M.,
M. Otsuki,
T. Nishino,
I. Kobayashi,
T. Matsumoto, and J. Kumazawa.
1996.
Mutation in DNA gyrase of norfloxacin-resistant clinical isolates of Neisseria gonorrhoeae.
Genitourin. Med.
72:295-297[Medline].
|
| 23.
|
Tanaka, M.,
K. Takahashi,
T. Saika,
I. Kobayashi,
T. Ueno, and J. Kumazawa.
1998.
Development of fluoroquinolone resistance and mutations involving GyrA and parC proteins among Neisseria gonorrhoeae isolates in Japan.
J. Urol.
159:2215-2219[CrossRef][Medline].
|
| 24.
|
Tanaka, M.,
H. Nakayama,
M. Haraoka,
T. Saika,
I. Kobayashi, and S. Naito.
2000.
Antimicrobial resistance of Neisseria gonorrhoeae and high prevalence of ciprofloxacin-resistant isolates in Japan, 1993 to 1998.
J. Clin. Microbiol.
38:521-525[Abstract/Free Full Text].
|
| 25.
|
Tapsall, J. W.,
E. A. Phillips,
T. R. Shultz, and C. Thacker.
1996.
Quinolone-resistant Neisseria gonorrhoeae isolated in Sydney, Australia, 1991 to 1995.
Sex. Transm. Dis.
23:425-428[Medline].
|
| 26.
|
Tapsall, J. W.,
E. A. Limnios, and T. R. Shultz.
1998.
Continuing evolution of the pattern of quinolone resistance in Neisseria gonorhoeae isolated in Sydney, Australia.
Sex. Transm. Dis.
25:415-417[Medline].
|
| 27.
|
Tenover, F. C.,
R. D. Arbeit, and R. V. Goering.
1997.
How to select and interpret molecular strain typing methods for epidemiological studies of bacterial infections: a review for healthcare epidemiologists.
Infect. Control Hosp. Epidemiol.
18:426-439[Medline].
|
| 28.
|
Trees, D. L.,
A. L. Sandul,
W. L. Whittington, and J. S. Knapp.
1998.
Identification of novel mutation patterns in the parC gene of ciprofloxacin-resistant isolates of Neisseria gonorrhoeae.
Antimicrob. Agents Chemother.
42:2103-2105[Abstract/Free Full Text].
|
| 29.
|
Trees, D. L.,
A. L. Sandul,
V. Peto-Mesola,
M. Aplasca,
H. B. Leng,
W. L. Whittington, and J. S. Knapp.
1999.
Alterations within the quinolone resistance-determining regions of GyrA and ParC of Neisseria gonorrhoeae isolated in the Far East and United States.
Int. J. Antimicrob. Agents
12:325-332[CrossRef][Medline].
|
| 30.
|
WHO Western Pacific Gonococcal Antimicrobial Surveillance Programme.
1998.
Resistance in gonococci isolated in the WHO Western Pacific region to various antimicrobials used in the treatment of gonorrhoea, 1997.
Commun. Dis. Intell.
22:288-291[Medline].
|
| 31.
|
World Health Organization.
1989.
STD treatment strategies. WHO/VDT/89.447.
World Health Organization, Geneva, Switzerland.
|
| 32.
|
Xia, M.,
M. C. Roberts,
W. L. Whittington,
K. K. Holmes,
J. S. Knapp,
J. R. Dillon, and T. Wi.
1996.
Neisseria gonorrhoeae with decreased susceptibility to ciprofloxacin: pulsed-field gel electrophoresis typing of strains from North America, Hawaii, and the Philippines.
Antimicrob. Agents Chemother.
40:2439-2440[Medline].
|
Antimicrobial Agents and Chemotherapy, January 2001, p. 117-123, Vol. 45, No. 1
0066-4804/01/$04.00+0 DOI: 10.1128/AAC.45.1.117-123.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
-
Wang, B., Xu, J.-s., Wang, C.-x., Mi, Z.-h., Pu, Y.-p., Hui, M., Ling, T. K. W., Chan, C.-Y.
(2006). Antimicrobial susceptibility of Neisseria gonorrhoeae isolated in Jiangsu Province, China, with a focus on fluoroquinolone resistance.. J Med Microbiol
55: 1251-1255
[Abstract]
[Full Text]
-
Ahmed, A. M, Kawamoto, H., Inouye, K., Hashiwata, Y., Sakaki, M., Seno, M., Shimamoto, T.
(2005). Genomic analysis of a multidrug-resistant strain of enterohaemorrhagic Escherichia coli O157 : H7 causing a family outbreak in Japan. J Med Microbiol
54: 867-872
[Abstract]
[Full Text]
-
Zhou, W., Du, W., Cao, H., Zhao, J., Yang, S., Li, W., Shen, Y., Zhang, S., Du, W., Zhang, X.
(2004). Detection of gyrA and parC Mutations Associated with Ciprofloxacin Resistance in Neisseria gonorrhoeae by Use of Oligonucleotide Biochip Technology. J. Clin. Microbiol.
42: 5819-5824
[Abstract]
[Full Text]
-
Yong, D., Kim, T. S., Choi, J. R., Yum, J. H., Lee, K., Chong, Y., Oh, H.-B., Shultz, T., Tapsall, J. W.
(2004). Epidemiological characteristics and molecular basis of fluoroquinolone-resistant Neisseria gonorrhoeae strains isolated in Korea and nearby countries. J Antimicrob Chemother
54: 451-455
[Abstract]
[Full Text]
-
Giles, J., Hardick, J., Yuenger, J., Dan, M., Reich, K., Zenilman, J.
(2004). Use of Applied Biosystems 7900HT Sequence Detection System and Taqman Assay for Detection of Quinolone-Resistant Neisseria gonorrhoeae. J. Clin. Microbiol.
42: 3281-3283
[Abstract]
[Full Text]
-
Kam, K. M., Kam, S. S. Y., Cheung, D. T. L., Tung, V. W. N., Au, W. F., Cheung, M. M.
(2003). Molecular Characterization of Quinolone-Resistant Neisseria gonorrhoeae in Hong Kong. Antimicrob. Agents Chemother.
47: 436-439
[Abstract]
[Full Text]
-
Ameyama, S., Onodera, S., Takahata, M., Minami, S., Maki, N., Endo, K., Goto, H., Suzuki, H., Oishi, Y.
(2002). Mosaic-Like Structure of Penicillin-Binding Protein 2 Gene (penA) in Clinical Isolates of Neisseria gonorrhoeae with Reduced Susceptibility to Cefixime. Antimicrob. Agents Chemother.
46: 3744-3749
[Abstract]
[Full Text]
Top
Abstract
Introduction
