Molecular features of heterogeneous vancomycin-intermediate Staphylococcus aureus strains isolated from bacteremic patients

Abstract

<p>Abstract</p> <p>Background</p> <p>Heterogeneous vancomycin-intermediate <it>Staphylococcus aureus </it>(hVISA) bacteremia is an emerging infection. Our objective was to determine the molecular features of hVISA strains isolated from bacteremic patients and to compare them to methicillin resistant <it>S. aureus </it>(MRSA) and methicillin sensitive <it>S. aureus </it>(MSSA) blood isolates.</p> <p>Results</p> <p>We assessed phenotypic and genomic changes of hVISA (n = 24), MRSA (n = 16) and MSSA (n = 17) isolates by PCR to determine staphylococcal chromosomal cassette (SCC<it>mec</it>) types, Panton-Valentine leukocidin (PVL) and the accessory gene regulator (<it>agr</it>) loci. Biofilm formation was quantified. Genetic relatedness was assessed by PFGE. PFGE analysis of isolates was diverse suggesting multiple sources of infection. 50% of hVISA isolates carried SCC<it>mec </it>type I, 21% type II; 25% type V; in 4% the SCC<it>mec </it>type could not be identified. Among MRSA isolates, 44% were SCC<it>mec </it>type I, 12.5% type II, 25% type V, 12.5% were non-typable, and 6% were SCC<it>mec </it>type IVd. Only one hVISA isolate and two MSSA isolates carried the PVL. Biofilm formation and <it>agr </it>patterns were diverse.</p> <p>Conclusion</p> <p>hVISA isolates were diverse in all parameters tested. A considerable number of hVISA and MRSA strains carried the SCC<it>mec </it>type V cassette, which was not related to community acquisition.</p