Abstract
Over the past few years, a dramatic increase in methicillin resistance of Staphylococcus aureus (MRSA) isolates has been observed worldwide. Infections due to MRSA cause higher rates of patient morbidity and mortality, longer hospital stays, and higher overall costs. Extensive infection control measures are necessary to prevent patient-to-patient transmission of MRSA. The sooner these infection ...
Abstract
Over the past few years, a dramatic increase in methicillin resistance of Staphylococcus aureus (MRSA) isolates has been observed worldwide. Infections due to MRSA cause higher rates of patient morbidity and mortality, longer hospital stays, and higher overall costs. Extensive infection control measures are necessary to prevent patient-to-patient transmission of MRSA. The sooner these infection control measures are taken, the lower is the probability of transmission between patients. Rapid identification of MRSA carriers is the fundamental task required to achieve this goal. Even sophisticated culture-based methods take at least 24 h to provide results. With the use of nucleic acid amplification technology, time-to-result periods of less than 3 h can be achieved under routine conditions. Although the originally developed PCR methods based on separate detection of the mecA gene and different S. aureus-specific markers are useful for molecular identification of MRSA, their diagnostic performance for direct detection of MRSA in clinical specimens is limited. More recently developed methods, which detect the integration event of a so-called SCCmec element (typically harbouring the mecA gene) into the S. aureus genome, are better suited for this purpose. At present, a number of different commercial and in-house PCR assays that rely on this innovative detection strategy are available. Although these assays usually display high levels of sensitivity (90-100%), specificity (93-99%) and positive predictive values (>95%), their negative predictive values are lower (80-95%). With the widespread use of these PCR assays, a number of intrinsic shortcomings have been identified that may lead to either false-positive or false-negative results. Therefore, an elaborate combination of molecular and culture-based methods should be implemented during routine laboratory workup for MRSA detection.
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