Comparative in vitro activity of isepamicin and other antibiotics against Gram-negative bacilli from intensive care units (ICU) in Belgium

The in vitro activity of isepamicin was compared to that of amikacin, gentamicin, cefepime, ciprofloxacin and meropenern against Gram-negative bacilli isolated from patients hospitalized in the intensive care unit (ICU) of 11 Belgian university or general hospitals between November 1998 and July 1999. The minimal inhibitory concentrations (MIC) for 1087 non-duplicate, consecutive aerobic Gram-negative isolates, including 798 Enterobacteriaceae and 289 non-fermenters, were determined by E-test for each antibiotic. Overall, isepamicin was active against 91% of all isolates and was found more active than ciprofloxacin (84% susceptibility), gentamicin (88% susceptibility), cefepime and amikacin (89% susceptibility each), but less active than meropenem (94% susceptibility). Enterobacter aerogenes isolates exhibited the highest resistance rate to ciprofloxacin (72%) while P. aeruginosa appeared the most resistant (frequently multi-resistant) pathogen. Compared to amikacin, MIC values for isepamicin were usually two- to fourfold lower for most inducible Enterobacteriacieae species and for Klebsiella spp., while they were identical for P. aeruginosa and other non-fermenters. Complete cross-susceptibility or cross-resistance between amikacin and isepamicin was observed in more than 95% of all tested isolates. On the other hand, 122% of all E. aerogenes isolates appeared resistant to amikacin and susceptible to isepamicin, while 6% of the P aeruginosa were found to be resistant (or intermediate) to isepamicin and intermediate (or susceptible) to amikacin. No significant differences in pathogen distribution nor in resistance rates were observed between hospitals except for P. aeruginosa. Taking into account the species distribution and the prevalence of resistance to the different antibiotics tested, isepamicin appears as a suitable agent for empiric therapeutic use in severe ICU-acquired Gram-negative infections in Belgium.