• J. Antimicrob. Chemother. · Nov 2009

    Multicenter Study

    Occurrence of vancomycin-tolerant and heterogeneous vancomycin-intermediate strains (hVISA) among Staphylococcus aureus causing bloodstream infections in nine USA hospitals.

    • Helio S Sader, Ronald N Jones, Kerri L Rossi, and Michael J Rybak.
    • JMI Laboratories, North Liberty, IA, USA. helio-sader@jmilabs.com
    • J. Antimicrob. Chemother. 2009 Nov 1; 64 (5): 1024-8.

    BackgroundThe bactericidal activities of vancomycin and daptomycin were evaluated in a large collection of methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia strains from nine major USA medical centres.ObjectivesTo evaluate the occurrence of heterogeneous vancomycin-intermediate S. aureus (hVISA) among MRSA strains tolerant to vancomycin and/or with increased vancomycin or daptomycin MIC values. The accuracy of the macro Etest method (MET) compared with population analysis profiling (PAP) for the detection of hVISA was also assessed.MethodsA total of 1800 MRSA strains were collected from bloodstream infections at the nine sites (40 strains per year, per medical centre during the 2002-06 study period). Vancomycin and daptomycin MIC testing was performed by reference broth microdilution (all strains) and MBC tests on 50% of strains (randomly selected). A subset of isolates (n = 268) having an increased vancomycin MBC (> or =16 mg/L), an increased vancomycin MIC (> or =1 mg/L) and/or an increased daptomycin MIC (>0.5 mg/L) were tested for susceptibility to vancomycin and teicoplanin by MET.ResultsOverall, 181 of 900 (20.1%) MRSA tested exhibited vancomycin tolerance, varying from 10% to 43% among the medical centres evaluated, and from 11.7% in 2004 to 27.8% in 2005. No resistance trend was observed in any medical centre or in the overall study data. Daptomycin showed bactericidal activity against all strains tested. The accuracy of MET for identifying hVISA strains varied significantly with the criteria applied for positivity.ConclusionsThe most frequently used criteria to define hVISA, i.e. MET reading values > or =8 mg/L for both vancomycin and teicoplanin or > or =12 mg/L for teicoplanin only, detected 20 of 36 PAP-positive strains (55.6% sensitivity), indicating that the prevalence of hVISA could be higher than currently appreciated. Daptomycin was bactericidal against hVISA strains.

      Pubmed     Full text   Copy Citation     Plaintext  

      Add institutional full text...

    Notes

     
    Knowledge, pearl, summary or comment to share?
    300 characters remaining
    help        
    You can also include formatting, links, images and footnotes in your notes
    • Simple formatting can be added to notes, such as *italics*, _underline_ or **bold**.
    • Superscript can be denoted by <sup>text</sup> and subscript <sub>text</sub>.
    • Numbered or bulleted lists can be created using either numbered lines 1. 2. 3., hyphens - or asterisks *.
    • Links can be included with: [my link to pubmed](http://pubmed.com)
    • Images can be included with: ![alt text](https://bestmedicaljournal.com/study_graph.jpg "Image Title Text")
    • For footnotes use [^1](This is a footnote.) inline.
    • Or use an inline reference [^1] to refer to a longer footnote elseweher in the document [^1]: This is a long footnote..

    hide…