Vancomycin-heteroresistant phenotype in invasive methicillin-resistant Staphylococcus aureus isolates belonging to spa type 041.
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.
Monaco
M
M
Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
Sanchini
A
A
Grundmann
H
H
Pantosti
A
A
D015373:Bacterial Typing Techniques / Q000379:methods; D016000:Cluster Analysis; D016172:DNA Fingerprinting / Q000379:methods; D004269:DNA, Bacterial / Q000235:genetics; D005838:Genotype; D006801:Humans; D007558:Italy / Q000453:epidemiology; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification* / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D020713:Vancomycin Resistance
D004269:DNA, Bacterial
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