cecropin-p1-li and ranalexin

The in vitro susceptibilities of 90 clinical isolates of gram-positive and gram-negative aerobic bacteria to six cationic peptides, buforin II, cecropin P1, indolicidin, magainin II, nisin, and ranalexin, were evaluated by two broth microdilution methods. The first method was performed according to the procedures outlined by the National Committee for Clinical Laboratory Standards for bacteria that grow aerobically, while the second was performed according to the procedures recently proposed by the R. E. W. Hancock laboratory for testing antimicrobial peptides. Overall, the first method produced MICs two- and fourfold higher than the second method.

Topics: Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Gram-Negative Aerobic Bacteria; Gram-Positive Bacteria; Magainins; Nisin; Peptides; Peptides, Cyclic; Proteins; Xenopus Proteins

The in vitro interaction between five polycationic peptides, buforin II, cecropin P1, indolicidin, magainin II, and ranalexin, and several clinically used antimicrobial agents was evaluated against several clinical isolates of Gram-positive and Gram-negative aerobic bacteria, using the microbroth dilution method. The combination studies showed synergy between ranalexin and polymyxin E, doxycycline and clarithromycin. In addition, magainin II was shown to be synergic with betalactam antibiotics.

Topics: Amino Acid Sequence; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Clarithromycin; Colistin; Doxycycline; Drug Interactions; Drug Resistance, Multiple; Escherichia coli; Gram-Negative Bacteria; Gram-Positive Bacteria; Lactams; Magainins; Molecular Sequence Data; Peptides; Peptides, Cyclic; Proteins; Pseudomonas aeruginosa; Staphylococcus aureus; Xenopus Proteins

The in-vitro activity of cecropin P1, indolicidin, magainin II, nisin and ranalexin alone and in combination with nine clinically used antimicrobial agents was investigated against a control strain, Pseudomonas aeruginosa ATCC 27853 and 40 clinical isolates of P. aeruginosa. Antimicrobial activities were measured by MIC, MBC and viable count. In the combination study, the clinically used antibiotics were used at concentrations close to their mean serum level in humans in order to establish the clinical relevance of the results. To select peptide-resistant mutants, P. aeruginosa ATCC 27853 was treated with consecutive cycles of exposure to each peptide at 1 x MIC. The peptides had a varied range of inhibitory values: all isolates were more susceptible to cecropin P1, while ranalexin showed the lowest activity. Nevertheless, synergy was observed when the peptides were combined with polymyxin E and clarithromycin. Consecutive exposures to each peptide at 1 x MIC resulted in the selection of stable resistant mutants. Cationic peptides might be valuable as new antimicrobial agents. Our findings show that they are effective against P. aeruginosa, and that their activity is enhanced when they are combined with clinically used antimicrobial agents, particularly with polymyxin E and clarithromycin.

Topics: Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Colony Count, Microbial; Drug Resistance, Microbial; Drug Synergism; Drug Therapy, Combination; Humans; Magainins; Microbial Sensitivity Tests; Nisin; Peptides; Peptides, Cyclic; Pseudomonas aeruginosa; Pseudomonas Infections; Xenopus Proteins

The in-vitro activity of cecropin P1, magainin II, indolicidin and ranalexin alone and in combination with macrolides and dihydrofolate reductase inhibitors (DHFRs) was investigated against six clinical isolates of Pneumocystis carinii. The susceptibility tests were performed by inoculation of the isolates on to cell monolayers and determining the parasite count after 72 h incubation at 37 degrees C. The culture medium was supplemented with serial dilutions of each agent. The four peptides suppressed the growth of cysts and trophozoites by > or = 50% at 20 microM and 2 microM, respectively, with the exception of indolicidin (cysts: IC50, 20 microM; trophozoites: IC50, 20 microM). The IC90 values of all peptides for either cysts or trophozoites were observed at a concentration of 20 microM. Our data showed that the activity of lytic peptides remained virtually unchanged when they were tested either alone or in combination with macrolides and DHFRs, with the exception of ranalexin: a cysts/trophozoites reduction in the range 77.3-85.1% was observed when ranalexin 2 microM was combined with 4 mg/L of macrolides. Our study suggests that lytic peptides may be effective in inhibiting the growth of P. carinii in vitro. In addition some of these compounds seem to have an effective interaction with hydrophobic antibiotics.

Topics: Anti-Bacterial Agents; Anti-Infective Agents; Antimicrobial Cationic Peptides; Drug Synergism; Folic Acid Antagonists; Humans; Macrolides; Magainins; Microbial Sensitivity Tests; Peptides; Peptides, Cyclic; Pneumocystis; Xenopus Proteins

Four peptides, cecropin P1, magainin II, indolicidin, and ranalexin, were evaluated against 202 clinical isolates of gram-positive and gram-negative aerobic bacteria by a microbroth dilution method. The gram-negative isolates were more susceptible to cecropin P1. Ranalexin was the most active compound against the gram-positive strains. The bactericidal activity of each peptide was equivalent to, or 1 dilution above, the MIC. In conclusion, the four peptides exhibited different in vitro activities and rapid time-dependent killing.

Topics: Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Gram-Negative Aerobic Bacteria; Gram-Positive Bacteria; Magainins; Microbial Sensitivity Tests; Peptides; Peptides, Cyclic; Time Factors; Xenopus Proteins