Multidrug-resistant gram-positive pathogens. An update on current microbiological patterns

Abstract

Although resistance has developed among Gram-positive pathogens to penicillins, cephalosporins, aminoglycosides, quinolones and macrolides, the glycopeptides seem to remain largely unaffected. However, the recent emergence and range of glycopeptide resistance in enterococci, well documented in the USA but not in the rest of the world, have prompted this European surveillance study. The European Glycopeptide Resistance Survey was undertaken in 1995 in 9 countries and involved 70 microbiological centres. The primary aims of the survey were as follows: (i) to perform a microbiological quality assurance assessment to evaluate the ability of participating laboratories to correctly identify the strains and assess their glycopeptide susceptibility; and (ii) to accurately determine the level of glycopeptide resistance among staphylococci, streptococci and enterococci in European hospitals. The in vitro activity of several other antibiotics was assessed on strains isolated from the Italian centres. In total, 7078 Gram-positive isolates were collected in Europe, and national coordinators used the National Committee for Clinical Laboratory Standards (NCCLS) agar dilution reference method to successfully retest 96% of these. According to mode minimum inhibitory concentrations (MICs), teicoplanin activity was similar to that of vancomycin against Staphylococcus aureus. In general, the range of MICs for teicoplanin was wider than that for vancomycin against coagulase-negative staphylococci. Against Enterococcus spp. and Streptococcus spp., teicoplanin was 4 times more active than vancomycin. The greatest number of glycopeptide refractory organisms was evident among enterococci; resistance was observed to be approximately 10 times more frequent in Enterococcus faecium than in E. faecalis. The results from the Italian isolates were similar to those from the overall study. In particular, teicoplanin was 2- to 8-fold more active than vancomycin against the majority of the enterococci. The incidence of enterococcal resistance was lower in Italy (0.6% for teicoplanin and 0.9% for vancomycin) than in Europe (1.7% for teicoplanin and 2.3% for vancomycin). This extensive survey confirms that teicoplanin is more active than vancomycin against enterococci and streptococci, and that both display similar potency against staphylococci.