Direct and fast detection of methicillin resistant Staphylococcus aureus carriage by automated nucleic acid extraction and real time PCR

We have developed a real time PCR assay for methicillin resistant Staphylococcus aureus (MRSA) screening able to provide a result in less than 3 h. The PCR amplifies a 184 bp fragment corresponding to the junction area between mecA and orfX genes that allows specific identification of MRSA in a nonsterile specimen. 1481 nasal swabs taken from geriatrics, dialysis and intensive care patients were compared with traditional bacteriology. A short centrifugation, preliminary to the extraction, with "SETS" system allows a recovery of the sample. The automated DNA extraction is carried out by the MagNA Pure LC And the PCR by the LightCycler. The agreement between the two methods is 97.7%. A study of sensitivity and specificity on I I I I samples respectively gives 75 and 98% for the real time PCR and, 64 and 99% for the culture. The strategy of fast and effective tracking that we propose is of an undeniable contribution in the fight against the MRSA infections. (c) 2006 Elsevier Masson SAS. Tons droits reserves