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BMC Research Notes

, 3:110

First Online: 21 April 2010Received: 25 February 2010Accepted: 21 April 2010DOI: 10.1186-1756-0500-3-110

Cite this article as: Kolman, S., Arielly, H. & Paitan, Y. BMC Res Notes 2010 3: 110. doi:10.1186-1756-0500-3-110


BackgroundMethicillin-resistant Staphylococcus aureus MRSA is a human pathogen, representing an infection control challenge. Conventional MRSA screening takes up to three days, therefore development of rapid detection is essential. Real time-PCR rt-PCR is the fastest method fulfilling this task. All currently published or commercially available rt-PCR MRSA assays relay on single or double-locus detection. Double-locus assays are based on simultaneous detection of mecA gene and a S. aureus-specific gene. Such assays cannot be applied on clinical samples, which often contain both coagulase-negative staphylococci CoNS and S. aureus, either of which can carry mecA. Single-locus assays are based on detection of the staphylococcal cassette chromosome mec SCCmec element and the S. aureus-specific orfX gene, assuming that it is equivalent to mecA detection.

FindingsParallel evaluation of several published single and double-locus rt-PCR MRSA assays of 150 pure culture strains, followed by analysis of 460 swab-derived clinical samples which included standard identification, susceptibility testing, followed by PCR detection of staphylococcal suspected isolates and in-PCR mixed bacterial populations analysis indicated the following findings.

Pure cultures analysis indicated that one of the single-locus assay had very high prevalence of false positives Positive predictive value = 77.8% and was excluded from further analysis. Analysis of 460 swab-derived samples indicated that the second single-locus assay misidentified 16 out of 219 MRSA-s and 13 out of 90 methicillin-sensitive S. aureus-s MSSA were misidentified as MRSA-s. The double-locus detection assay misidentified 55 out of 90 MSSA-s. 46 MSSA containing samples were misidentified as MRSA and 9 as other than S. aureus ending with low positive predicted value <85% and very low specificity <62%.

ConclusionThe results indicate that high prevalence of false-positive and false-negative reactions occurs in such assays.

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Autor: Sara Kolman - Haya Arielly - Yossi Paitan

Fuente: https://link.springer.com/

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