In Vitro Antimicrobial Activity Against Enterococci Isolated in a University Hospital in São Paulo, Brazil

The prevalence of multiresistant enterococci (MRE) is rapidly increasing and becoming an important problem in several countries. São Paulo Hospital is a 600-bed tertiary hospital located in São Paulo, Brazil. The use of vancomycin is very high in the hospital due to the high prevalence of multi-resistant S. aureus (around 70%). We susceptibility tested 250 isolates of Enterococci consecutively collected between March, 1994 and June, 1995. Isolates were susceptibility tested using agar dilution disc diffusion BHI screen plating, and E test. In addition to vancomycin and teicoplanin, the isolates were tested against ampicillin, gentamicin, streptomycin and RP 59-500. Methods used for susceptibility testing were compared. None of the isolates showed high-level resistance to vancomycin or teicoplanin. The MIC90s for teicoplanin were <e;1µg/mL for E. faecalis (EF, n=216), E. faecium (EFM, n=23) and for the non-faecalis-non-faecium (NFNF, n=11) species. The MlC90s for vancomycin were 2µg/mL, 4µg/mL and 4µg/mL for EF, EFM and NFNF respectively. Eight isolates (3.2%), 5 E. faecalis, 2 E. casseliflavus and 1 E. gallinarum presented intermediate MICs for vancomycin (6 - 12µg/mL), but they were highly susceptible to teicoplanin (MIC 0.19 - 1µg/mL). The percentage of resistance to ampicillin and high-level resistance to gentamicin and streptomycin were, respectively: 4.8%, 26.4%, and 24.8%. In spite of the high usage of vancomycin in our hospital, the prevalence of glycopeptide resistance among enterococci seems to be low. Teicoplanin appears to be more potent than vancomycin, RP 59-500, gentamicin, streptomycin and ampicilin against this genus, especially EFM and NFNF species.