Control of meticillin-resistant Staphylococcus aureus (MRSA) and the value of rapid tests

The cornerstones of infection control are the identification of patients who are contagious for others, and taking appropriate control measures. Microbiological detection of pathogens can take from several minutes or hours (microscopy) up to several days (culture-dependent detection). Currently, meticillin-resistant Staphylococcus aureus (MRSA) is one of the most important pathogens in nosocomial infection control, and detection using culture will take 1 5 days. This delay in the result of culture leads to a suboptimal control strategy. In low endemic settings like The Netherlands, patients who are considered at increased risk of MRSA carriage are treated in isolation until the results of culture have confirmed the absence of MRSA. On average this will take 4 to 5 days. As approximately 95% of these patients will not carry MRSA, this leads to a high number of unnecessary isolation days. This could be reduced by a rapid diagnostic test. In high endemic settings, admission screening and isolation until proven negative reduces the incidence of MRSA in high-risk units of the hospital. This has been predicted in a mathematical model and has been confirmed in intervention studies. Such a strategy can be implemented much more efficiently when a rapid diagnostic test is available. Recently, a real-time polymerase chain reaction test has become available that can detect MRSA directly from patient samples and takes less than 2 hours. The first results have been encouraging, although there are strains that are not detected. This test is not primarily intended to be used as a diagnostic device but rather as a screening tool for infection control. Many other screening tests are under development which may prove useful tools for the optimization of infection control in the near future.