title: Antibacterial and anti-biofilm activities of melittin and colistin, alone and in combination with antibiotics against Gram-negative bacteria.
abstract: In vitro antibacterial and anti-biofilm activities of antimicrobial cationic peptides (AMPs) - melittin and colistin - both alone and in combination with antibiotics were evaluated against clinical isolates of Gram-negative bacteria. Minimum inhibitory concentration (MIC) and fractional inhibitory concentration (FIC) index were determined by the microbroth dilution and chequerboard techniques, respectively. The time-kill curve (TKC) method was used for determining the bactericidal activities of AMPs alone and in combination. Measurements of anti-biofilm activities were performed spectrophotometrically for both inhibition of attachment and 24-hour biofilm formation at MIC or subMIC. According to MIC90 values, the most active agents against Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae were colistin, imipenem and ciprofloxacin, respectively. In combination studies, synergistic effects were mostly seen with colistin-imipenem against E. coli and K. pneumoniae (50 and 54%, respectively), colistin-ciprofloxacin against P. aeruginosa (77%). In TKC studies, synergism was observed with almost all expected combinations, even more frequently than chequerboard method. All of the antimicrobial agents were able to inhibit attachment and 24-hour biofilm formation between 0-57% at 1/10 × MIC and 7-73% at 1 × or 1/10 × MIC, respectively. AMPs seem to be a good candidate for antimicrobial chemotherapy with their antibacterial and anti-biofilm activities as a single agent or in combination with antibiotics.
authors: a Faculty of Pharmacy, Department of Pharmaceutical Microbiology , University of Istanbul , Beyazit , Turkey.
authors: Sibel
authors: S
authors: Dosler
authors: b Faculty of Medicine, Department of Medical Microbiology , University of Bezmi Alem , Fatih , Istanbul , Turkey.
authors: Elif
authors: E
authors: Karaaslan
authors: a Faculty of Pharmacy, Department of Pharmaceutical Microbiology , University of Istanbul , Beyazit , Turkey.
authors: A
authors: A
authors: Alev Gerceker
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D003091:Colistin / Q000494:pharmacology*; D004347:Drug Interactions; D004926:Escherichia coli / Q000187:drug effects / Q000302:isolation & purification; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology; D006801:Humans; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000302:isolation & purification; D008555:Melitten / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D008555:Melitten; D003091:Colistin
keywords: Antibiotic; Colistin; Gram-negative bacteria; Inhibition of biofilm; Melittin