Antibiotic susceptibility patterns and serotypes of antibiotic resistant and/or invasive Streptococcus pneumoniae strains circulating in Italy.

Antibiotic susceptibility patterns and serotypes of 397 Streptococcus pneumoniae recovered from 1994 to 1998 in Italy have been determined. This collection included 229 penicillin- and/or erythromycin-resistant strains and 168 isolates responsible for invasive infections. Among penicillin-resistant pneumococci, the most prevalent serotype was 23F, followed by 19F and 9V, while among erythromycin-resistant but penicillin-susceptible strains serotype 6B was predominant followed by 19A, 14, 19F, 15A, 15B, and 23F. The most common invasive serotypes were 6B, 19F, 23F, 3, 4, 14, 20, 15B, and 9N. The currently available 23-valent pneumococcal vaccine could cover 91% of noninvasive penicillin- and/or erythromycin-resistant strains, 84% of pneumococci isolated from sterile sites, and 83% of invasive antibiotic-resistant S. pneumoniae. Penicillin-resistant pneumococci also showed reduced susceptibility to other antimicrobial compounds. Against invasive pneumococci, amoxicillin, cefotaxime, ceftriaxone, imipenem, vancomycin, and rifampin were 100% effective. Penicillin, chloramphenicol, erythromycin, tetracycline, and co-trimoxazole resistance was 1.8%, 9.5%, 15.5%, 18.5%, and 21.4%, respectively.

Heterogeneous vancomycin resistance in methicillin-resistant Staphylococcus aureus strains isolated in a large Italian hospital.

Of 179 methicillin-resistant Staphylococcus aureus strains isolated from 1997 to 1998, two strains (1.1%) gave subclones for which the vancomycin MICs were 8 mg/liter. Pulsed-field gel electrophoresis showed identical restriction patterns for both isolates, suggesting transfer of a single clone between two different patients.

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

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.