A Comparative Analysis of GeneXpert Real-Time PCR with Culture for the Detection of Methicillin-Resistant Staphylococcus aureus Colonization in Selected Hospital Admissions

Abstract

Contact isolation of patients with methicillin-resistant Staphylococcus aureus (MRSA) reduces transmission to other patients and to health care workers. PCR technology can provide rapid detection of these patients. We tested the utility of using PCR for MRSA detection in patients with a history of MRSA infection or colonization or in a high risk group admitted to a general referral hospital. Nasal swabs from 342 patients were tested for MRSA on days one and three using the GeneXpert MRSA system. Swabs with a positive PCR result were cultured to identify staphylococcal species present in the nares. Fifty-six patients (38% of 147) with a history of MRSA colonization or infection were positive; forty-seven patients (24% of 195) in a high risk group were positive. Eighty-one percent of the patients with positive PCR swabs grew out MRSA on culture. Some cultures grew out only methicillin-sensitive Staphylococcus aureus, methicillin-sensitive, coagulase negative Staphylococcus, or methicillin-resistant, coagulase negative Staphylococcus. This study demonstrates that most patients at risk for MRSA colonization are not colonized and that microbiological surveillance using PCR technology can facilitate contact isolation decisions. Not all PCR positive results represent the presence of MRSA, and hospitals need to consider policies for additional evaluation of positive PCR tests.