Susceptibility patterns of enterococci causing infections

Enterococci are among the common organisms associated with hospital-acquired infections. We examined in vitro activities of different antibiotics to 103 enterococcal isolates. Minimal inhibitory concentrations (MICs) of penicillin G, ampicillin, gentamicin, ciprofloxacin, ofloxacin, levofloxacin, grepafloxacin, trovafloxacin and gemifloxacin were determined by broth microdilution testing method. Among the isolates 71 (69%) were identified as E. faecalis and 32 (31%) as E. faecium. While over 75% of E. faecium isolates were resistant to penicillin and ampicillin, approximately 25% of E. faecalis isolates were resistant to penicillin and ampicillin. None of the E. faecalis and E. faecium isolates were resistant to vancomycin. While 17 (52%) of E. faecium isolates exhibited high-level gentamicin resistance (HLGR), high level streptomycin resistance (HLSR) was detected in 24 (74%) of the isolates. In contrast, HLGR and HLSR rates for E. faecalis were 14 (20%) and 22 (31%), respectively. Both HLGR and HLSR were detected with higher frequency in ampicillin resistant isolates. Among fluoroquinolones, gemifloxacin and trovafloxacin were the most potent antibiotics tested. There was no increase in MIC90 values of the fluoroquinolones in ampicillin resistant isolates in comparison with ampicillin susceptible isolates. Our data suggest newer fluoroquinolones would be good alternative agents to use especially for combination drug therapy where enterococci with ampicillin resistance and HLAR are prevalent.