In vitro antimicrobial susceptibility to isepamicin of 6,296 Enterobacteriaceae clinical isolates collected at a tertiary care university hospital in Greece.

The reevaluation of "forgotten" antibiotics can identify new therapeutic options against extensively drug-resistant Gram-negative pathogens. We sought to investigate isepamicin in this regard. We retrospectively evaluated the antimicrobial susceptibility to isepamicin of Enterobacteriaceae sp. isolates from unique patients, collected at the microbiological laboratory of the University Hospital of Heraklion, Crete, Greece, from 2004 to 2009. Susceptibility testing was done with the automated Vitek 2 system. The breakpoints for susceptibility to isepamicin, tigecycline, and other antibiotics were those proposed by the Comité de l'Antibiogramme de la Société Française de Microbiologie (CA-SFM), the FDA, and the CLSI, respectively. A total of 6,296 isolates were studied, including primarily 3,401 (54.0%) Escherichia coli, 1,040 (16.5%) Klebsiella pneumoniae, 590 (9.4%) Proteus mirabilis, and 460 (7.3%) Enterobacter sp. isolates. Excluding the species with intrinsic resistance to each antibiotic, antimicrobial susceptibility was highest for colistin (5,275/5,441 isolates [96.9%]) and isepamicin (6,103/6,296 [96.9%]), followed by meropenem (5,890/6,296 [93.6%]), imipenem (5,874/6,296 [93.3%]), and amikacin (5,492/6,296 [87.2%]). The antimicrobial susceptibility of the 1,040 K. pneumoniae isolates was highest for isepamicin (95.3%), followed by colistin (89.3%) and meropenem (63.0%). Regarding resistant K. pneumoniae isolates, susceptibility to isepamicin was observed for 91.1% of the 392, 87.7% of the 375, and 85.6% of the 111 isolates that were nonsusceptible to the carbapenems, all other aminoglycosides, and colistin, respectively. Isepamicin exhibited high in vitro activity against almost all of the Enterobacteriaceae species. It could particularly serve as a last-resort therapeutic option for carbapenem-resistant K. pneumoniae in our region, where it is endemic, as it does not show considerable cross-resistance with other aminoglycosides.