Antibiotic resistances and plasmids in Staphylococcus aureus from Italian hospitals

Abstract

Summary.A total of 473 Staphylococcus aureus isolates from six Italian hospitals was examined for susceptibility to several antimicrobial agents and for plasmid content. Methicillin-resistant S . aureus (MRSA) were characterised by a plasmid of mol. wt (lo6) 18-22 or 25 that carried the determinants for penicillinase production, resistance to cadmium ions and resistance to tetracycline. MRSA isolates usually harboured other smaller plasmids of mol. wt (lo6) 2.8, 2.6 and 1-45 that encoded resistance to tetracycline, chloramphenicol and erythromycin, respectively, and cryptic plasmids of mol. wt (lo6) c. 2 and 1 were found frequently. Methicillin-sensitive S . aureus (MSSA) that produced penicillinase often carried plasmids of mol. wt (lo6) 11 or 13. No particular difference was found in plasmid patterns of strains from the various sources. Analysis of plasmids by EcoRI digestion showed that plasmids of similar mol. wt and phenotypic characteristics may have different restriction patterns, but often share one or more fragments in common.

Characterization of a novel insertion of the macrolides-lincosamides-streptogramin B resistance transposon Tn554 in methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis

“…Mcr staphylococci have frequently been found to be MLS' in other studies (9,39,43), but no correlation with a particular TnS54 insert has been reported previously. In the extensively studied Australian Mcr prototype strain S. aureus ANS46, MLS' determinants have not been found in the mec-associated DNA (11,21).…”

Differentiation of Staphylococcal Species and Strains by Ribosomal RNA Gene Restriction Patterns

“…Other methods that have been applied include plasmid profile analysis (Archer et al, 1984;Gelmi et al, 1987), phage typing (de Saxe et al, 1981;Vindel et al, 1987), DNA base composition (Kocur et al, 1971) and antibiotic susceptibility (Schito & Varaldo, 1988). However, these methods are not always able to discriminate usefully between species.…”

Epidemiology of Methicillin-Resistant <i>Staphylococcus aureus</i>

“…Some MRSA strains lack plasmids and are, therefore, nontypable. Many isolates carry only one or two plasmids, which provides poor discriminatory power and plasmid bearing strains may change or even lose their plasmid contents [62,[78][79][80]. Commercially available kits, however, allow a fast typing, which can help to identify an outbreak early.…”