In vitro activity of isepamicin and other aminoglycosides against clinical isolates of Gram-negative bacteria causing nosocomial bloodstream infections.

BACKGROUND AND PURPOSE Isepamicin is a newly introduced aminoglycoside in Taiwan. Since in vitro data for isepamicin against nosocomial Gram-negative bloodstream infection from Taiwan are limited, we compared the activity of isepamicin, amikacin, gentamicin and tobramycin against nosocomial Gram-negative blood isolates. METHODS A total of 247 non-duplicate nosocomial blood isolates of Gram-negative bacteria collected between January 2003 and December 2003 in a major teaching hospital in Taiwan were tested for their in vitro susceptibilities to gentamicin, tobramycin, amikacin, and isepamicin using the agar dilution method. The isolates included Escherichia coli (31 isolates), Klebsiella pneumoniae (31), Enterobacter cloacae (30), Serratia marcescens (31), Morganella morganii (21), Citrobacter freundii (10), Pseudomonas aeruginosa (31), Acinetobacter baumannii (31), and Stenotrophomonas maltophilia (31). RESULTS Overall, isepamicin had high antibacterial activity against the tested Gram-negative bacteria. For the 154 Enterobacteriaceae isolates, isepamicin had the lowest minimum concentration inhibiting 90% of isolates (MIC90) among the tested drugs, while its resistance rate (3.9%) was equal to that of amikacin (3.9%) and lower than those of tobramycin (18.2%) and gentamicin (21.4%). For the 93 of non-fermentative Gram-negative bacilli isolates, isepamicin had the lowest MIC90, and a resistance rate (23.7%) lower than those of amikacin (27.9%), tobramycin (38.7%) and gentamicin (40.9%). CONCLUSIONS The in vitro activity of isepamicin against Gram-negative bacteria isolates was equal or similar to amikacin and superior to other tested aminoglycosides. In view of its potential for less nephrotoxicity and ototoxicity than other aminoglycosides, isepamicin is a drug of choice for the empirical treatment of nosocomial infections caused by Gram-negative bacteria.