Comparative in vitro activity of tigecycline and nine other antibiotics against Gram-negative bacterial isolates, including ESBL-producing strains.

AbstractThe Enterobacteriaceae, especially Escherichia coli and Klebsiella spp., as well as Acinetobacter spp., are important agents of nosocomial infections in hospitalized patients. A total of 460 Gram-negative bacteria (GNB), were investigated for their susceptibility to tigecycline and 9 other antibiotics by the etest. ESBL production was inferred from ESBL etest phenotypes. All the GNB, including the ESBL-producers, were susceptible to tigecycline with MIC90 ranges of 0.25 to 2 μg/ml. imipenem and meropenem were very active against ESBL and non-ESBL producers; mean MIC90s of 0.19 and 0.09 μg/ml and 0.05 μg/ml and 0.02 μg/ml, respectively. The MIC90s of imipenem and meropenem for the Acinetobacter spp. were 16 and ≤32 μg/ml, respectively with resistance rates of 64.3 and 66.1%. ESBL production was detected in 62% and 82.1% of the E. coli and K. pneumoniae isolates, respectively. Resistance to ciprofloxacin was higher among the ESBL-producing strains of E. coli and K. pneumoniae than the non-ESBL produ...