Susceptibility of staphylococci and enterococci to glycopeptides comparison of 3 test methods.
The significance of grampositive bacteria, especially staphylococci and enterococci, as nosocomial pathogens has increased in the last decade. Furthermore, resistance to commonly used antibiotics like beta-lactams has also become more common and even resistance to glycopeptides has been observed. We evaluated the susceptibility of 150 staphylococcal clinical isolates (52 S. epidermidis, 52 S. haemolyticus, 10 S. saprophyticus, 10 S. hominis, 4 S. warneri, 4 S. simulans, 4 S. capitis and 14 S. aureus) and of 50 enterococci (49 E. faecalis, 1 E. faecium) to the glycopeptides, vancomycin and teicoplanin. The data from the agar dilution test used as reference method were compared with the results from the E test and the agar disk diffusion test. Concerning vancomycin, no resistance among all the staphylococcal isolates was observed whereas one single enterococcal strain (E. faecium) proved to be resistant. The overall resistance of staphylococcal isolates against teicoplanin was about 10.7% (15 S. haemolyticus, 1 S. epidermidis) being mainly due to the high proportion of S. haemolyticus strains (52 out of 150) among the staphylococcal isolates. Teicoplanin resistance among the enterococci was not detected. For vancomycin, a very close correlation between the MICs from the agar dilution test and the E test was noticed. As concerns teicoplanin, the MICs from the E-test were usually somewhat lower than those obtained by the agar dilution test. No correlation was found between the MICs of resistant and intermediate staphylococcal strains and the results from the teicoplanin agar disk diffusion test. For routine teicoplanin susceptibility testing of staphylococci, the determination of the MIC (e.g., by the E test) is much more reliable for detecting resistant strains than the agar disk diffusion test.
Jansen
B
B
Institute of Medical Microbiology and Hygiene, University of Cologne, Köln, Germany.
Schumacher-Perdreau
F
F
Pulverer
G
G
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016983:Enterococcus / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D013210:Staphylococcus / Q000187:drug effects*; D017334:Teicoplanin / Q000494:pharmacology*; D014640:Vancomycin / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D017334:Teicoplanin; D014640:Vancomycin