Use of real-time polymerase chain reaction for identification of methicillin-resistant Staphylococcus aureus directly from positive blood culture bottles.

The utility of real-time polymerase chain reaction (RT-PCR) testing for detection of methicillin-resistant Staphylococcus aureus (MRSA) directly from positive blood culture bottles was evaluated. One hundred forty-two blood cultures showing Gram-positive cocci in clusters were detected. Each blood culture sample was tested for the presence of MRSA by PCR analysis (SmartCycler) via detection of the mecA and orfX genes. In parallel, they were plated on standard media for identification and characterization. PCR analysis directly from the blood culture bottle required a total time of 120 min (45 min for preparation and 75 min for the reaction). By comparison, conventional laboratory procedures required between 48 and 72 h. The overall test accuracy was 97% with a high positive likelihood ratio and a low negative likelihood ratio.