Previous Article | Next Article 
Antimicrobial Agents and Chemotherapy, April 1999, p. 782-788, Vol. 43, No. 4
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
In Vitro Antibacterial Properties of Pexiganan, an Analog
of Magainin
Yigong
Ge,1,*
Dorothy L.
MacDonald,1
Kenneth J.
Holroyd,1
Clyde
Thornsberry,2
Hannah
Wexler,3 and
Michael
Zasloff1
Magainin Pharmaceuticals Inc., Plymouth
Meeting, Pennsylvania 194621; MRL
Pharmaceutical Services, Franklin, Tennessee
370642; and Wadsworth Anaerobe
Laboratories, Los Angeles, California 900733
Received 22 July 1998/Returned for modification 2 October
1998/Accepted 14 January 1999
 |
ABSTRACT |
Pexiganan, a 22-amino-acid antimicrobial peptide, is an analog of
the magainin peptides isolated from the skin of the African clawed
frog. Pexiganan exhibited in vitro broad-spectrum antibacterial activity when it was tested against 3,109 clinical isolates of gram-positive and gram-negative, anaerobic and aerobic bacteria. The
pexiganan MIC at which 90% of isolates are inhibited
(MIC90) was 32 µg/ml or less for
Staphylococcus spp., Streptococcus spp., Enterococcus faecium, Corynebacterium spp.,
Pseudomonas spp., Acinetobacter spp.,
Stenotrophomonas spp., certain species of the family
Enterobacteriaceae, Bacteroides spp.,
Peptostreptococcus spp., and Propionibacterium
spp. Comparison of the MICs and minimum bactericidal concentrations
(MBCs) of pexiganan for 143 isolates representing 32 species
demonstrated that for 92% of the isolates tested, MBCs were the same
or within 1 twofold difference of the MICs, consistent with a
bactericidal mechanism of action. Killing curve analysis showed that
pexiganan killed Pseudomonas aeruginosa rapidly, with
106 organisms/ml eliminated within 20 min of treatment with
16 µg of pexiganan per ml. No evidence of cross-resistance to a
number of other antibiotic classes was observed, as determined by the equivalence of the MIC50s and the MIC90s
of pexiganan for strains resistant to oxacillin, cefazolin,
cefoxitin, imipenem, ofloxacin, ciprofloxacin, gentamicin, and
clindamicin versus those for strains susceptible to these antimicrobial
agents. Attempts to generate resistance in several bacterial species
through repeated passage with subinhibitory concentrations of pexiganan
were unsuccessful. In conclusion, pexiganan exhibits properties in
vitro which make it an attractive candidate for development as a
topical antimicrobial agent.
| |
INTRODUCTION |
A recently emerged class of
antibiotics with potential for use as human therapeutic agents is the
antimicrobial peptides of animal origin (7). Over the past
15 years, more than 100 antimicrobial peptides, including magainins,
cecropins, protegrins, and defensins, have been discovered in animals
ranging from insects to humans (16, 20, 26). These peptides
represent components of the system of host defense commonly called
"innate immunity" and are used by animals to effectively deal
with microbes in their environment (2, 9, 19, 21).
Antimicrobial peptides selectively damage the membranes of bacteria
through mechanisms which bacteria should theoretically find difficult
to evade (2, 7, 16, 17). Among these animal-derived
antibiotics are the magainins, discovered in the skin of the African
clawed frog Xenopus laevis more than 12 years ago (8,
9, 12, 22, 24, 26). Through a series of amino acid substitutions
and deletions, pexiganan (MSI-78) was constructed. Pexiganan exhibited
an enhanced potency relative to that of magainin 2 against both
gram-positive and gram-negative bacteria in several preliminary studies
(3, 9). Pexiganan has been developed as a therapeutic
antimicrobial agent for the topical treatment of infected diabetic foot
ulcers (10).
In this paper, we report on the aspects of the in vitro activity of
pexiganan relevant to its use as a topical anti-infective agent. A
total of 3,109 clinical isolates including gram-positive and
gram-negative microbes were screened for their susceptibilities to
pexiganan. The results indicate that pexiganan is a broad-spectrum bactericidal peptide antibiotic.
| |
MATERIALS AND METHODS |
Organisms.
The microbial isolates tested were predominantly
recent clinical isolates obtained from hospitals throughout the United States.
Agents.
The pexiganan
(Gly-Ile-Gly-Lys-Phe-Leu-Lys-Lys-Ala-Lys-Lys-Phe-Gly-Lys-Ala-Phe-Val-Lys-Ile-Leu-Lys-Lys-NH2;
molecular weight, 2478 [free peptide base]) used in the study was
chemically synthesized by solid-phase procedures and was purified
chromatographically by previously described procedures (26)
at either Magainin Pharmaceuticals Inc. (MPI) or Bachem Bioscience
(Torrance, Calif.). MSI-214, a peptide identical in sequence to
pexiganan but comprising all D-amino acids, was synthesized
and purified at MPI. Both pexiganan and MSI-214 were dissolved in
deionized water before use. Imipenem was purchased from Merck Sharp & Dohme Research Laboratories (Rahway, N.J.), and ciprofloxacin was
purchased from Miles, Inc. (West Haven, Conn.). Other antimicrobial
agents were supplied by Sigma Chemical Co. (St. Louis, Mo.).
Mueller-Hinton broth (MHB) and nutrient broth were supplied by Becton
Dickinson Microbiology Systems (Cockeysville, Md.).
Antimicrobial testing.
The antimicrobial tests were carried
out at three testing sites: MPI in Plymouth Meeting, Pa.; MRL
Pharmaceutical Services Inc. in Franklin, Tenn. (the testing laboratory
site is in Cypress, Calif.); and the Wadsworth Anaerobe Laboratory in
Los Angeles, Calif. The method used to determine the MICs was the
National Committee for Clinical Laboratory Standards (NCCLS) broth
microdilution assay in microtiter plates (14, 15), with the
exception that some isolates were initially tested (at the MPI site) in
a total broth volume of 200 µl instead of 100 µl. In order to avoid
any potential effect of cations in the test medium on the antimicrobial activity of pexiganan, the broth used for the testing of most aerobic
bacteria with pexiganan was unsupplemented MHB. Anaerobe MIC broth
(Wilkins-Chalgrin) was generally used in the MIC assays for anaerobic
bacteria. If needed, 3% horse serum was added to the broth for MIC
assays with anaerobic bacteria. The susceptibility and resistance
breakpoints for the antibiotics other than pexiganan were based on
NCCLS guidelines.
The minimum bactericidal concentrations (MBCs) were determined
according to NCCLS guidelines (13). The killing curve assay was performed on the basis of a previously published standard protocol
(11). The experiment was done in duplicate. Cells from the
logarithmic phase of growth were collected and were incubated at 37°C
with different concentrations of pexiganan in a total volume of 5 ml of
cation-adjusted MHB (105 to 106 organisms/ml).
At different time points, 0.1 ml of the culture was collected and was
mixed with 25 ml of molten agar for the preparation of agar pour
plates. Since the drug had been diluted at least 250-fold in the
plates, the antibiotic carryover effect was minimal. In addition, to
obtain appropriate numbers of CFU in an individual plate (fewer than
150 colonies/plate) to ensure accurate colony counting, 0.2 ml of the
culture was taken from different time points, and a series of 10-fold
dilutions (10
1 to 107) was prepared. Then,
0.1 ml of these diluted cells was used to prepare the plates as
described above. The plates were incubated overnight at 37°C.
In vitro resistance study.
In brief, the in vitro passage
study involved the incorporation of pexiganan into Mueller-Hinton
agarose at a concentration of one-half the previously established MIC
determined by a broth microdilution assay. Agarose was used to replace
agar as the support matrix in the in vitro passage study since our
preliminary experimental results indicated that alginic acid, a major
anionic component in agar, binds to pexiganan and significantly
inhibits its antimicrobial activity (data not shown). The organisms
were cultured in duplicate on the agarose plates (both
antibiotic-containing and control plates) for 7 to 14 sequential
passages. For each organism, the MIC was determined prior to the
initiation of the study, after the 4th passage, after the 7th passage,
and in some cases, after the 11th and 14th passages. If the MIC after
the fourth passage was greater than 1 twofold dilution higher than the
original MIC, then for passes 5, 6, and 7, the amount of pexiganan in
the agarose was increased to one-half of that new MIC. A similar
approach was also used in the instances in which 14 passages were conducted.
| |
RESULTS AND DISCUSSION |
In vitro antibacterial activity.
A total of 3,108 clinical
isolates were tested, including 2,692 aerobes and 416 anaerobes. The
MICs at which 50 and 90% of isolates are inhibited (MIC50s
and MIC90s) and the distributions of MICs for these
organisms are summarized in Table
1. Pexiganan demonstrated potency against
gram-positive and gram-negative aerobes and anaerobes. Among all the
gram-positive aerobic microbes tested except Streptococcus
sanguis and Enterococcus faecalis, 90% of staphylococci, streptococci, vancomycin-resistant Enterococcus faecium (VREF), Micrococcus spp., and
Corynebacterium spp. were inhibited by pexiganan at
a concentration of 16 µg/ml or less. Pexiganan exhibited potency
against the majority of gram-negative aerobic bacteria tested, such as
members of the family Enterobacteriaceae, Pseudomonas spp., Acinetobacter baumannii, and
Stenotrophomonas maltophilia, and 90% of clinical isolates
of these species were inhibited by pexiganan at 64 µg/ml or
less. Three species (Alcaligenes faecalis, S. sanguis, and E. faecalis) were less sensitive to pexiganan (MIC90s, 
256 µg/ml), but the
MIC50s of pexiganan for these three species were 16 µg/ml (A. faecalis), 64 µg/ml (S. sanguis), and 128 µg/ml (E. faecalis). The
anaerobes tested, including Clostridium spp.,
Peptostreptococcus spp., Bacteroides spp.,
Prevotella spp., Fusobacterium nucleatum, and
Propionibacterium acnes, were generally more sensitive to
pexiganan than aerobic bacteria, and 90% of these isolates
were inhibited by pexiganan at a concentration of 64 µg/ml or less. Pexiganan was most active against
Bacteroides spp. and P. acnes, with an
MIC90 of 
8 µg/ml.
In order to establish reference MICs for pexiganan, we tested a
number of strains from the American Type Culture Collection
(ATCC) for
their sensitivities to pexiganan. As indicated in Table
2, the MICs for the ATCC strains were
generally consistent with
those for the clinical isolates tested (Table
1 and
2). Of these
ATCC strains,
Haemophilus influenzae,
Helicobacter pylori,
Streptococcus pneumoniae,
and
Veillonella parvula, clinical strains of which
had not
been tested in this study, were also inhibited by pexiganan
(MICs,
32 µg/ml). The MIC of pexiganan was >256
µg/ml for
Proteus mirabilis and
Serratia
marcescens, as noted previously for magainins
(
26).
The broad antibacterial spectrum of pexiganan is consistent
with the antibacterial spectrum previously observed for antimicrobial
peptides of animal origin (
2,
7,
9) and confirms a recently
published preliminary study of the activity of pexiganan
(
3).
The antimicrobial spectrum of pexiganan is
broader than those
of the current commercially available peptide
antibiotics, such
as polymyxin B or polymyxin E. Although the
antimicrobial activities
of polymyxin and pexiganan against
many species of gram-negative
bacteria are comparable, polymyxin
exhibits no significant activity
against gram-positive bacteria, such
as staphylococci (
11).
Use of pexiganan composed of all D-amino acids
(MSI-214) to elucidate mechanisms of resistance.
MSI-214 is an
analog of pexiganan. Its amino acid sequence is identical to
that of pexiganan, but it is composed of all
D-amino acids and it is resistant to the actions of known
natural peptidases (1, 23). To understand whether
proteolytic degradation plays a role in the resistance of certain
bacterial species to pexiganan, we compared the MIC of
pexiganan with that of MSI-214 for nine species. Included were
comparisons of both more sensitive organisms (i.e., VREF and
Micrococcus luteus) and less sensitive organisms (i.e.,
P. mirabilis and S. marcescens). As shown in
Table 2, the differences in MICs between the L and the
D forms of pexiganan were less than 2 twofold
dilutions for the same species of bacterium. MSI-214 showed a slightly
enhanced activity only against E. faecalis. In addition,
intact pexiganan peptide could be recovered from the culture
medium following overnight growth of P. mirabilis and
S. marcescens (data not shown). The data suggest that
elaboration of proteolytic enzymes is not a primary mechanism for the
generation of bacterial resistance to pexiganan. Analogous to
other antimicrobial peptides of animal origin, the natural
resistance to pexiganan in some species may be explained by a
failure of the peptide to interact with either the inner or the outer
membrane or by the action of a peptide-transporting efflux pump
(4-6, 18).
Potency against antibiotic-resistant strains.
Along with
pexiganan, several other classes of antibiotics were also
tested against the isolates, including cephalosporins, carbapenems, fluoroquinolones, lincosamides, and aminoglycosides. These data were used to determine whether strains that are
resistant to other classes of antibiotics and strains that are
susceptible to other classes of antibiotics have differences in
sensitivity to pexiganan. Among the isolates tested, a
significant number of resistant bacteria were included:
oxacillin-resistant staphylococci (175 isolates), ofloxacin-resistant
staphylococci (70 isolates), cefazolin-resistant staphylococci (19 isolates), imipenem-resistant staphylococci (18 isolates),
imipenem-resistant Pseudomonas spp. (24 isolates),
ciprofloxacin-resistant Pseudomonas spp. (22 isolates), gentamicin-resistant Pseudomonas spp. (17 isolates),
ciprofloxacin-resistant Acinetobacter baumannii (34 isolates), clindamycin-resistant Clostridium spp. (35 isolates), and cefoxitin-resistant Bacteroides spp. (11 isolates). There were no significant differences in the
MIC50s and MIC90s of pexiganan for
those strains resistant to oxacillin, cefazolin, cefoxitin,
imipenem, ofloxacin, ciprofloxacin, gentamicin, and
clindamicin and the MIC50s and MIC90s of
pexiganan for those strains susceptible to these
antimicrobial agents. With respect to the peptide antibiotics polymyxin
B and polymyxin E, only more limited studies were conducted. For three
clinical isolates of P. aeruginosa that were resistant
to polymyxin B (MICs 32 to 128 µg/ml) and polymyxin E (MICs, 256 to >256 µg/ml), pexiganan MICs were identical to those
for nonresistant strains of Pseudomonas aeruginosa.
Non-cross-resistance between polymyxin B and a magainin peptide has
been observed elsewhere (25), suggesting subtle differences
in the mechanisms of action of different classes of peptide
antimicrobial agents. Taken together, the results indicate that no
evidence of cross-resistance between pexiganan and the other
commonly used antimicrobial agents was observed.
Effect of culture conditions on antimicrobial activity of
pexiganan.
Since the initial interaction between a
cationic peptide and the membrane of the target cell is electrostatic
in nature, the antibiotic activity of pexiganan as a function
of the pH of the medium was explored. In an assay conducted in nutrient
broth, 30 clinical isolates of P. aeruginosa (9 isolates),
Staphylococcus aureus (11 isolates), and
Staphylococcus epidermidis (10 isolates) were tested at pHs
ranging from 5.0 to 8.0. No notable difference in potency was observed,
although a modest increase in MICs, found at pH 5.5 with S. aureus, was noted (Table 3). These
results indicate that the fundamental antimicrobial activity of
pexiganan does not notably decrease with changes in pH.
One possible concern with the use of a cationic antimicrobial peptide
such as pexiganan is its possible inactivation by serum,
either
through the action of proteases or through interactions
with proteins
or lipids. To determine the effect of serum on the
antimicrobial
activity of pexiganan, the MIC of pexiganan was
evaluated in the presence of sera from various animals (Table
4). Against the three species of
organisms tested, human serum
had a minimal effect on the activity of
pexiganan, with the changes
in the MIC being less than twofold.
In contrast, mouse serum completely
eliminated the activity of
pexiganan, while sera from other animals
inhibited the activity
of pexiganan at various levels. In a separate
experiment, we
compared heat-inactivated mouse serum with fresh
mouse serum. The
heat-treated (55°C for 30 min) serum exhibited
markedly reduced
inhibitory activity, with the MICs falling from
>256 µg/ml
(unheated serum) to 16 µg/ml (heat-treated serum) for
S. aureus and from 256 µg/ml (unheated serum) to
32 to 64 µg/ml
(heat-treated serum) for
E. coli.
The original MICs in MHB for
the species tested were 2 µg/ml
(
S. aureus) and 4 µg/ml (
E. coli).
A heat-sensitive component in mouse serum appears to be, at
least
in part, responsible for inactivation of the antimicrobial
activity
of pexiganan. These observations are relevant to in
vivo studies
with this and related peptides, since the infected mouse
is a
commonly used animal model of antibiotic efficacy.
Bactericidal activity.
The difference between the MICs and the
MBCs has been established as an index of the bactericidal activity of
an antibiotic (11). A total of 143 isolates representing 32 aerobic species were tested to determine both the MICs and the MBCs of
pexiganan. As indicated in Table
5, of 143 isolates tested, MBCs were the same or within 1 doubling dilution higher of the MICs for 132 (92%)
isolates. For only two isolates of S. sanguis were MBCs increased more than 4 twofold dilutions. These findings are consistent with a bactericidal mechanism of action for pexiganan.
The bactericidal action of antibiotic peptides such as
pexiganan is thought to result from irreversible
membrane-disruptive
damage (
2,
7,
9). On the basis of the
mechanism of action
of magainin, pexiganan would be
expected to exert its antimicrobial
action rapidly, as
reported previously for related molecules (
26).
The kinetics
of bacterial killing were evaluated against four
species
(
E. coli,
S. aureus,
P. aeruginosa, and VREF) at three
concentrations of
pexiganan (1×, 4×, and 16× the MIC). Cell viability
within
the first 2 h was measured. As shown in Fig.
1, for all
four species, the rate of
bacterial killing was dependent on the
concentration of
pexiganan, with greater than 10
5
organisms/ml being eradicated (reductions to <5 CFU/ml) within
2 h with the highest concentration studied. Bacterial cultures
were monitored for up to 24 h, and no regrowth was observed;
for
all four species tested, no colony was found after 0.2 ml of
the
24-h cultures was plated. The best activity was found against
P. aeruginosa: more than 10
6 P. aeruginosa organisms/ml were eradicated within 20 min with
16 µg
of pexiganan per ml (1× the MIC). The results indicate that
at
appropriate concentrations, pexiganan is a rapidly acting
bactericidal
agent. Bactericidal action occurs, as assessed with
S. aureus,
E. coli,
P. aeruginosa, and VREF, and was clearly dependent on
the
concentration of pexiganan to which the organisms were exposed.
View larger version (26K):
[in this window]
[in a new window]
|
FIG. 1.
Killing curve study. The killing activity of
pexiganan against four ATCC strains was monitored for the first
2 h. (a) Escherichia coli ATCC 25922; (b)
Enterococcus faecium ATCC 51559 (vancomycin resistant); (c)
Staphylococcus aureus ATCC 29213; (d) Pseudomonas
aeruginosa ATCC 27853. For P. aeruginosa, the
killing curves were identical (overlapping in the figure) for 4× the
MIC and 16× the MIC. Under the assay conditions used in this study,
the lowest detectable level was 5 CFU/ml.
|
|
In vitro development-of-resistance studies.
To explore the
development of resistance to pexiganan in vitro, two selection
procedures were conducted. In the first procedure, several organisms
were passed repeatedly in the presence of concentrations of
pexiganan insufficient to effect complete killing, a process which selects for rare resistant mutants that may exist or develop in a
population. For a total of 27 clinical isolates representing eight
bacterial species (Table 6), after seven
sequential passages in the presence of subinhibitory concentrations of
pexiganan, the change in average MICs for individual isolates
and species was less than twofold. In addition, the in vitro
development of resistance to pexiganan was compared to that to
two other topical antibiotics, mupirocin and fusidic acid, for several
species. After seven passages in vitro in the presence of subinhibitory concentrations of mupirocin, there were increases in the MICs for two
S. aureus isolates (a 64-fold increase for the
mupirocin-susceptible strain and an 8-fold increase for the
mupirocin-resistant strain). In contrast, no increase in the MICs was
observed for the same isolates treated with pexiganan. A
similar pattern was also seen with fusidic acid. After 14 in
vitro passages in the presence of subinhibitory concentrations of
fusidic acid with two isolates (one S. aureus isolate
and one S. epidermidis isolate), resistance to fusidic
acid developed in both isolates: the MICs rose from 0.06 to 64 to 128 µg/ml (S. aureus) and from 0.06 to 128 µg/ml (S. epidermidis). In contrast, no change in
the MIC was seen for isolates exposed to pexiganan. The results
of these experiments, which were limited in terms of the scope of
isolates and species tested, indicate that in vitro resistance acquired
by the selection of mutations within the population of a given
bacterial isolate may occur with mupirocin and fusidic acid but, for
the same isolate, not with pexiganan. Consistent with this
concept, antimicrobial peptides of animal origin have previously been
suggested to possess a low potential for the induction of bacterial
resistance (7).
In a second selection procedure, we intentionally introduced genomic
mutations in vitro by exposure of
S. aureus and
P. aeruginosa to either a chemical mutagen or UV light.
No pexiganan-resistant
mutants were produced by either chemical
or UV mutagenesis (data
not
shown).
Thus, the development of increased resistance of an isolate to
pexiganan, through multiple-passage studies or mutagenesis,
has
not been observed, as noted both in this study and in the
course of
many years of experimentation (
27). In addition, no
evidence
exists, either through our own observations or within
the
published literature, of the transfer of a resistance phenotype
between
an intrinsically resistant and susceptible isolate through
either
chromosomal or plasmid-mediated
mechanisms.
In conclusion, pexiganan, an analog of the animal-derived
antibiotic magainin, has been shown to exhibit broad-spectrum
microbicidal
activity and acts with a bactericidal mechanism against
which
the likelihood of the development of resistance may be low. In
addition, no evidence of cross-resistance to a number of other
antibiotic classes was observed, as determined by the equivalence
of the MIC
50s and MIC
90s of pexiganan
for those strains resistant
to oxacillin, cefazolin, cefoxitin,
imipenem, ofloxacin, ciprofloxacin,
gentamicin, and clindamicin
and the MIC
50s and MIC
90s of pexiganan
for those strains susceptible to these antimicrobial agents. These
in
vitro properties have made pexiganan an attractive candidate
for development as a topical antimicrobial agent (
7,
9,
10).
| |
ACKNOWLEDGMENTS |
We thank D. York for technical assistance with the antimicrobial
assays and R. Waldron for assistance in review of the manuscript.
| |
FOOTNOTES |
*
Corresponding author. Mailing address: Department of
Microbiology, Magainin Pharmaceuticals Inc., Plymouth Meeting, PA
19462. Phone: (610) 941-4013. Fax: (610) 941-5399. E-mail:
yge{at}magainin.com.
| |
REFERENCES |
| 1.
|
Bessalle, R.,
A. Kapitkovshy,
A. Gorea,
I. Shalit, and M. Fridkin.
1990.
All D-magainin: chirality antimicrobial activity, and proteolytic resistance.
FEBS Lett.
274:151-155[Medline].
|
| 2.
|
Boman, H. G.
1995.
Peptide antibiotics and their role in innate immunity.
Annu. Rev. Immunol.
13:61-92[Medline].
|
| 3.
|
Fuchs, P. C.,
A. L. Barry, and S. D. Brown.
1998.
In vitro antimicrobial activity of MSI-78, a magainin analog.
Antimicrob. Agents Chemother.
42:1213-1216[Abstract/Free Full Text].
|
| 4.
|
Groisman, E. A.
1994.
How bacteria resist killing by host-defense peptides.
Trends Microbiol.
2:444-449[Medline].
|
| 5.
|
Groisman, E. A., and A. Aspedon.
1995.
The genetic basis of microbial resistance to antimicrobial peptides.
Methods Mol. Biol.
78:205-215.
|
| 6.
|
Gunn, J. S.,
K. B. Lim,
J. Krueger,
K. Kim,
M. Hackett, and S. I. Miller.
1998.
PmrA-PmrB-regulated genes necessary for 4-aminoarabinose lipid A modification and polymyxin resistance.
Mol. Microbiol.
27:1171-1182[Medline].
|
| 7.
|
Hancock, R. E. W.
1997.
Peptide antibiotics.
Lancet
349:418-422[Medline].
|
| 8.
|
Iwahori, A.,
Y. Hirota,
P. Sampe,
S. Miyano,
N. Takahashi,
M. Sasatsu,
I. Kondo, and N. Numao.
1997.
On the antibacterial activity of normal and reversed magainin 2 analogs against Helicobacter pylori.
Biol. Pharm. Bull.
20:805-808[Medline].
|
| 9.
|
Jacob, L., and M. Zasloff.
1994.
Potential therapeutic application of magainins and other antimicrobial agents for animal origin.
Ciba Found. Symp.
186:197-216[Medline].
|
| 10.
|
Lipsky, B. A.,
P. A. Litka,
M. Zasloff,
K. Nelson, and the MSI-78-303 and 304 Study Group.
1997.
Microbial eradication and clinical resolution of infected diabetic foot ulcers treated with topical MSI-78 vs. oral ofloxacin, abstr. LM-57, p. 374.
In
Program and abstracts of the 37th Interscience Conference on Antimicrobial Agents and Chemotherapy. American Society for Microbiology, Washington, D.C.
|
| 11.
|
Lorian, V.
1996.
Antibiotics in laboratory medicine.
The Williams & Wilkins Co., Baltimore, Md.
|
| 12.
|
Ludtke, S. J.,
W. Heller,
T. A. Harroun,
L. Yang, and H. W. Huang.
1996.
Membrane pores induced by magainin.
Biochemistry
35:13723-13728[Medline].
|
| 13.
|
National Committee for Clinical Laboratory Standards.
1987.
Methods for determining bactericidal activity of antimicrobial agents. Proposed guideline (M26-P). Approved standard (M11-A3).
National Committee for Clinical Laboratory Standards, Wayne, Pa.
|
| 14.
|
National Committee for Clinical Laboratory Standards.
1993.
Methods for antimicrobial susceptibility testing of anaerobic bacteria, 3rd ed. Approved standard (M11-A3).
National Committee for Clinical Laboratory Standards, Wayne, Pa.
|
| 15.
|
National Committee for Clinical Laboratory Standards.
1997.
Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically, 4th ed. Approved standard (M7-A4).
National Committee for Clinical Laboratory Standards, Wayne, Pa.
|
| 16.
|
Nicolas, P., and A. Mor.
1995.
Peptides as weapons against microorganisms in the chemical defense system of vertebrates.
Annu. Rev. Microbiol.
49:277-304[Medline].
|
| 17.
|
Nissen-Meyer, J., and I. F. Nes.
1997.
Ribosomally synthesized antimicrobial peptides: their function, structure, biogenesis, and mechanism of action.
Arch. Microbiol.
167:67-77.
|
| 18.
|
Peterson, A. A.,
S. W. Fesik, and E. J. McGroarty.
1987.
Decreased binding of antibiotics to lipopolysaccharides from polymyxin-resistant strains of Escherichia coli and Salmonella typhimurium.
Antimicrob. Agents Chemother.
31:230-237[Abstract/Free Full Text].
|
| 19.
|
Schonwetter, B. S.,
E. D. Stolzenberg, and M. A. Zasloff.
1995.
Epithelial antibiotics induced at sites of inflammation.
Science
267:1645-1648[Abstract/Free Full Text].
|
| 20.
|
Steinberg, D. A.,
M. A. Hurst,
C. A. Fujii,
H. C. Kung,
J. F. Ho,
F. C. Cheng,
D. J. Loury, and J. C. Fiddes.
1997.
Protegrin-1: a broad-spectrum, rapidly microbicidal peptide with in vivo activity.
Antimicrob. Agents Chemother.
41:1738-1742[Abstract].
|
| 21.
|
Stolzenberg, E. D.,
G. M. Anderson,
M. R. Ackermann,
R. H. Whitlock, and M. Zasloff.
1997.
Epithelial antibiotic induced in states of disease.
Proc. Natl. Acad. Sci. USA
94:8686-8690[Abstract/Free Full Text].
|
| 22.
|
Tytler, E. M.,
G. M. Anantharamaiah,
D. E. Walker,
V. K. Mishra,
M. N. Palgunachari, and J. P. Segrest.
1995.
Molecular basis for prokaryotic specificity of magainin-induced lysis.
Biochemistry
34:4393-4401[Medline].
|
| 23.
|
Wade, D.,
A. Boman,
B. Wahlin,
C. M. Drain,
D. Andreu,
H. G. Boman, and R. B. Merrifield.
1990.
All-D amino acid-containing channel-forming antibiotic peptides.
Proc. Natl. Acad. Sci. USA
87:4761-4765[Abstract/Free Full Text].
|
| 24.
|
Wenk, M. R., and J. Seelig.
1998.
Magainin 2 amide interaction with lipid membranes: calorimetric detection of peptide binding and pore formation.
Biochemistry
37:3909-3916[Medline].
|
| 25.
| Wright, S. Personal communication.
|
| 26.
|
Zasloff, M.
1987.
Magainins, a class of antimicrobial peptides from Xenopus skin: isolation, characterization of two active forms, and partial cDNA sequence of a precursor.
Proc. Natl. Acad. Sci. USA
84:5449-5453[Abstract/Free Full Text].
|
| 27.
| Zasloff, M., D. MacDonald, and Y. Ge. Unpublished
data.
|
Antimicrobial Agents and Chemotherapy, April 1999, p. 782-788, Vol. 43, No. 4
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
-
Zaknoon, F., Sarig, H., Rotem, S., Livne, L., Ivankin, A., Gidalevitz, D., Mor, A.
(2009). Antibacterial Properties and Mode of Action of a Short Acyl-Lysyl Oligomer. Antimicrob. Agents Chemother.
53: 3422-3429
[Abstract]
[Full Text]
-
Jang, S. A, Sung, B. H., Cho, J. H., Kim, S. C.
(2009). Direct Expression of Antimicrobial Peptides in an Intact Form by a Translationally Coupled Two-Cistron Expression System. Appl. Environ. Microbiol.
75: 3980-3986
[Abstract]
[Full Text]
-
Kulkarni, M. M., McMaster, W. R., Kamysz, W., McGwire, B. S.
(2009). Antimicrobial Peptide-induced Apoptotic Death of Leishmania Results from Calcium-de pend ent, Caspase-independent Mitochondrial Toxicity. J. Biol. Chem.
284: 15496-15504
[Abstract]
[Full Text]
-
Sarig, H., Rotem, S., Ziserman, L., Danino, D., Mor, A.
(2008). Impact of Self-Assembly Properties on Antibacterial Activity of Short Acyl-Lysine Oligomers. Antimicrob. Agents Chemother.
52: 4308-4314
[Abstract]
[Full Text]
-
Pranting, M., Negrea, A., Rhen, M., Andersson, D. I.
(2008). Mechanism and Fitness Costs of PR-39 Resistance in Salmonella enterica Serovar Typhimurium LT2. Antimicrob. Agents Chemother.
52: 2734-2741
[Abstract]
[Full Text]
-
Hawrani, A., Howe, R. A., Walsh, T. R., Dempsey, C. E.
(2008). Origin of Low Mammalian Cell Toxicity in a Class of Highly Active Antimicrobial Amphipathic Helical Peptides. J. Biol. Chem.
283: 18636-18645
[Abstract]
[Full Text]
-
Tran, D., Tran, P., Roberts, K., Osapay, G., Schaal, J., Ouellette, A., Selsted, M. E.
(2008). Microbicidal Properties and Cytocidal Selectivity of Rhesus Macaque Theta Defensins. Antimicrob. Agents Chemother.
52: 944-953
[Abstract]
[Full Text]
-
Chongsiriwatana, N. P., Patch, J. A., Czyzewski, A. M., Dohm, M. T., Ivankin, A., Gidalevitz, D., Zuckermann, R. N., Barron, A. E.
(2008). Peptoids that mimic the structure, function, and mechanism of helical antimicrobial peptides. Proc. Natl. Acad. Sci. USA
105: 2794-2799
[Abstract]
[Full Text]
-
Rotem, S., Radzishevsky, I., Mor, A.
(2006). Physicochemical properties that enhance discriminative antibacterial activity of short dermaseptin derivatives.. Antimicrob. Agents Chemother.
50: 2666-2672
[Abstract]
[Full Text]
-
Jenssen, H., Hamill, P., Hancock, R. E. W.
(2006). Peptide Antimicrobial Agents. Clin. Microbiol. Rev.
19: 491-511
[Abstract]
[Full Text]
-
Rodriguez-Hernandez, M. J., Saugar, J., Docobo-Perez, F., de la Torre, B. G., Pachon-Ibanez, M. E., Garcia-Curiel, A., Fernandez-Cuenca, F., Andreu, D., Rivas, L., Pachon, J.
(2006). Studies on the antimicrobial activity of cecropin A-melittin hybrid peptides in colistin-resistant clinical isolates of Acinetobacter baumannii. J Antimicrob Chemother
58: 95-100
[Abstract]
[Full Text]
-
Rydlo, T., Rotem, S., Mor, A.
(2006). Antibacterial Properties of Dermaseptin S4 Derivatives under Extreme Incubation Conditions. Antimicrob. Agents Chemother.
50: 490-497
[Abstract]
[Full Text]
-
Perron, G. G, Zasloff, M., Bell, G.
(2006). Experimental evolution of resistance to an antimicrobial peptide. Proc R Soc B
273: 251-256
[Abstract]
[Full Text]
-
Radzishevsky, I. S., Rotem, S., Zaknoon, F., Gaidukov, L., Dagan, A., Mor, A.
(2005). Effects of Acyl versus Aminoacyl Conjugation on the Properties of Antimicrobial Peptides. Antimicrob. Agents Chemother.
49: 2412-2420
[Abstract]
[Full Text]
-
Cuthbertson, B. J., Yang, Y., Bachere, E., Bullesbach, E. E., Gross, P. S., Aumelas, A.
(2005). Solution Structure of Synthetic Penaeidin-4 with Structural and Functional Comparisons with Penaeidin-3. J. Biol. Chem.
280: 16009-16018
[Abstract]
[Full Text]
-
Giacometti, A., Ghiselli, R., Cirioni, O., Mocchegiani, F., D'Amato, G., Orlando, F., Sisti, V., Kamysz, W., Silvestri, C., Naldoski, P., Lukasiak, J., Saba, V., Scalise, G.
(2004). Therapeutic efficacy of the magainin analogue MSI-78 in different intra-abdominal sepsis rat models. J Antimicrob Chemother
54: 654-660
[Abstract]
[Full Text]
-
Balaban, N., Gov, Y., Giacometti, A., Cirioni, O., Ghiselli, R., Mocchegiani, F., Orlando, F., D'Amato, G., Saba, V., Scalise, G., Bernes, S., Mor, A.
(2004). A Chimeric Peptide Composed of a Dermaseptin Derivative and an RNA III-Inhibiting Peptide Prevents Graft-Associated Infections by Antibiotic-Resistant Staphylococci. Antimicrob. Agents Chemother.
48: 2544-2550
[Abstract]
[Full Text]
-
Won, H.-S., Jung, S.-J., Kim, H. E., Seo, M.-D., Lee, B.-J.
(2004). Systematic Peptide Engineering and Structural Characterization to Search for the Shortest Antimicrobial Peptide Analogue of Gaegurin 5. J. Biol. Chem.
279: 14784-14791
[Abstract]
[Full Text]
-
Arzese, A., Skerlavaj, B., Tomasinsig, L., Gennaro, R., Zanetti, M.
(2003). Antimicrobial activity of SMAP-29 against the Bacteroides fragilis group and clostridia. J Antimicrob Chemother
52: 375-381
[Abstract]
[Full Text]
-
Miller, K., O'Neill, A. J., Chopra, I.
(2002). Response of Escherichia coli hypermutators to selection pressure with antimicrobial agents from different classes. J Antimicrob Chemother
49: 925-934
[Abstract]
[Full Text]
-
Navon-Venezia, S., Feder, R., Gaidukov, L., Carmeli, Y., Mor, A.
(2002). Antibacterial Properties of Dermaseptin S4 Derivatives with In Vivo Activity. Antimicrob. Agents Chemother.
46: 689-694
[Abstract]
[Full Text]
-
O'Neill, A. J., Chopra, I., Martínez, J. L., Baquero, F.
(2001). Use of Mutator Strains for Characterization of Novel Antimicrobial Agents. Antimicrob. Agents Chemother.
45: 1599-1600
[Full Text]
Top
Abstract
Introduction
