The trend and susceptibility to antibacterial agents of enterococcus species from urinary tract infections

OBJECTIVE: To determine the extent of drug-resistance among Enterococcus species we investigated in vitro experiments. METHODS: Studies were carried out on pure cultured of enterococci isolated from 8,575 urine specimens between 1990 and 2002. We had determined test strains to three kinds of species, which posses the urinary pathogenesis. Both an EF-agars and an ADH decarboxylase test performed the identification and speciation of the strains of enterococci. In vitro drug-susceptibility tests of enterococci were performed against the following antibiotics: ampicillin (ABPC), cefpirome (CPR), cefozopran (CZOP), imipenem/cilastatin (IPM/CS), minocycline (MINO), levofloxacin (LVFX), vancomycin (VCM), sulfamethoxazone/trimethoprim (ST), by employing the method for dilution antimicrobial susceptibility tests for bacteria that grow aerobically recommended by Japan Society of Chemotherapy. These drug-susceptibilities were shown susceptible, intermittent and resistant in according to National Committee for Clinical Laboratory Standards (M100-S12). RESULTS: The most common species isolated was E. faecalis (84.4%), followed by E. faecium (9.9%) and E. avium (5.6%). In E. faecium and E. avium, the sensitivity to ABPC has tended to improve from 1999. This tendency inverse correlated to decreasing dosage of PCs. There was much difference of resistant rate to IPM/CS between each species, and no correlation to used dosage of CBPs. The rate of resistance to MINO did not change during this period. 60% of E. faecalis had sensitivity to LVFX and the rate did not change during this period. In E. faecium, whose resistant rate to LVFX was 90%, the sensitivity has been improved to over 25% from 2001. The improved tendency of E. faecium to LVFX has inverse proportion to decreasing dosage of NQs. With the exception of a little bit VRE (VCM resistant Enterococci), almost of them had sensitivity to VCM. CONCLUSION: The emergence of enterococci with alarming rates of resistance concomitantly to multi-drugs highlights the need for a more rational and restricted use of antimicrobials, in order to minimize the selection and spread of such strains. An early detection of these problem pathogens is also important for preventing any treatment failures.