Clinical utility of the Xpert MRSA assay for early detection of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for many nosocomial and community-acquired infections, resulting in significant morbidity and mortality. A practical way to limit the spread of MRSA is early detection and proper treatment. However, screening culture for MRSA typically requires 2–3 days. The Xpert MRSA assay (Cepheid, Sunnyvale, CA, USA) is a real-time polymerase chain reaction-based assay developed for screening an MRSA-specific DNA sequence within the staphylococcal cassette chromosome in 2 h. Lower respiratory tract specimens, such as transtracheal aspirates (TTAs) and bronchoalveolar lavage fluid (BALF), are commonly obtained from intubated patients. Therefore, using the lower respiratory tract specimens with the Xpert MRSA assay may be a practical tool for patient care. We performed the Xpert MRSA assay on 108 TTA and 21 BALF specimens from 92 patients and compared the results to those obtained by culture. The two assays showed concordant results in 120 (93.0%) cases and discordant results in 9 (7.0%) cases, which were culture-negative and Xpert MRSA-positive. Among the discordant cases, 5 patients developed culture-positive samples 2–15 days after the Xpert MRSA detected MRSA. We conclude that the Xpert MRSA assay is a rapid, sensitive and clinically useful test, particularly for the early detection of MRSA.