Antimicrobial activity of omiganan pentahydrochloride tested against contemporary bacterial pathogens commonly responsible for catheter-associated infections

Abstract

Omiganan pentahydrochloride is a cidal cationic peptide with a broad antimicrobial spectrum, including yeast, currently in development as a topical agent for the prevention of catheter-associated infections. We evaluated the spectrum and potency of omiganan against pathogens commonly associated with such infections. A recent (2005-06) collection of bacterial isolates originating from patients with bloodstream, respiratory tract, and skin and skin structure infections in US medical centres was evaluated by reference broth microdilution methods against omiganan and comparator agents. All tested gram-positive (390) and -negative (167) isolates were inhibited by < or = 128 and < or = 1024 mg/L, respectively, of omiganan. The agent was the most active against coagulase-negative staphylococci (range 1-8 mg/L; MIC(50/90), 4 mg/L) and inhibited all Staphylococcus aureus at < or = 32 mg/L (MIC(50/90), 16 mg/L). Omiganan was 16-fold more active against Enterococcus faecium than Enterococcus faecalis (MIC(50/90) results, 4/8 versus 64/128 mg/L, respectively). MIC ranges and MIC(50) potencies were unaffected by methicillin resistance in staphylococci, vancomycin resistance in enterococci, and penicillin resistance in streptococci. Omiganan potency was also unaffected by extended-spectrum beta-lactamase (ESBL) production in Escherichia coli when compared with wild-type strains (MIC(50) values 32 mg/L), although a 4-fold increase was noted among ESBL-positive Klebsiella spp. (128 versus 32 mg/L, respectively). Wild-type Enterobacter spp. displayed higher omiganan MIC(50/90) results (64/512 mg/L) compared with AmpC-hyperproducing strains (32/64 mg/L). Carbapenem-susceptible and -resistant P. aeruginosa strains exhibited omiganan MIC(50/90) values of 128/256 mg/L. At a 1% (10 000 mg/L) topical gel formulation, omiganan can be expected to inhibit all clinically relevant bacterial species producing catheter-associated infections (all MIC values, < or = 1024 mg/L), including those with antimicrobial-resistant phenotypes.