Antimicrobial susceptibility pattern of Enterococcus species from urinary tract infections

To determine the extent of drug-resistance among Enterococcus species in, in vitro experiments. Test strains were isolated from cases with urinary tract infection. Antimicrobial sensitivity was determined with particular reference to the beta-lactams, glycopeptide and aminoglycoside groups of antibiotics.

Studies were carried out on pure cultures of enterococci isolated from urine specimens of 147 patients. Freshly voided, aseptically collected, midstream specimens of urine were cultured by using standard techniques. The identification and speciation of the strains of enterococci were performed by employing a battery of tests. In vitro drug-susceptibility tests of enterococci were performed against the following antibiotics: penicillin, ampicillin, ampi-sulbactum, co-amoxi-clavulanate, ciprofloxacin, vancomycin, teicoplanin, gentamicin and streptomycin, by employing the disk diffusion method. MIC values for penicillin, ampicillin, vancomycin and teicoplanin against enterococci were determined by the agar dilution technique. MIC determinations were further carried out by the E-test method, for the glycopeptide antibiotics. Prevalence of high level resistance to aminoglycoside antibiotics was determined by the agar dilution method.

The most common species isolated was E. faecalis (87.07%), followed by E. faecium (10.88%) and E. durans (2.05%). The magnitude of resistance to both penicillin and ampicillin among the Enterococcus spp. was 23.13%, and that to ciprofloxacin was 55.78%. The three antibiotics: nitrofurantoin, co-amoxi-clavulanate, and ampi-sulbactum, showed resistance of 0.78%, 8.16% and 2.72%, respectively. High-level aminoglycoside resistance among strains of enterococci for streptomycin and gentamicin was found to be 33.84% and 36.92%, respectively. All the strains were susceptible to the glycopeptide antibiotics tested.

The emergence of enterococci with alarming rates of resistance concomitantly to penicillins and aminoglycosides 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.