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Eur J Clin Microbiol Infect Dis. 2010 Jul;29(7):771-7. doi: 10.1007/s10096-010-0922-2. Epub 2010 Apr 18.

Vancomycin-heteroresistant phenotype in invasive methicillin-resistant Staphylococcus aureus isolates belonging to spa type 041.

Author information

1
Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.

Abstract

The aim of this study was to characterise invasive methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains from Italy and to investigate the presence of heteroresistant vancomycin-intermediate S. aureus (h-VISA). Eighty-two MSSA and 66 MRSA strains obtained from 19 laboratories were submitted to in vitro susceptibility testing; MRSA strains were also analysed by the macro Etest (MET) and vancomycin population analysis profiles (PAP) to detect the presence of h-VISA. Genotyping included the detection of agr locus, SCCmec typing, spa typing and multilocus sequence typing (MLST). By Etest, 66% of all isolates showed a minimum inhibitory concentration (MIC) >or=1.5 microg/ml and two MRSA strains were categorised as VISA (MIC = 3 microg/ml). Twelve MRSA strains were positive by MET; of these, 9 (14% of all MRSA) were confirmed as h-VISA by PAP. MRSA strains were assigned to 14 spa types, with t001, t008 and t041 including 77% of the isolates. The most common spa type, t041, characterised as ST228/273-MRSA-I (CC5) and comprising 24 isolates, included one VISA and eight h-VISA. This is the first description of a close association between h-VISA and t041, a spa type common in Italy and in other European countries, that highlights the importance of molecular typing to identify clones of special clinical relevance.

PMID:
20401508
DOI:
10.1007/s10096-010-0922-2
[Indexed for MEDLINE]

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