Nasal methicillin-resistant Staphylococcus aureus polymerase chain reaction: a potential use in guiding antibiotic therapy for pneumonia.

CONTEXT: The role at admission of nasal polymerase chain reaction (PCR) for patients with methicillin-resistant Staphylococcus aureus (MRSA) in guiding antibiotic therapy for lower respiratory tract infection is unknown.

OBJECTIVE

To determine whether nasal MRSA PCR at admission can predict the absence of MRSA in lower respiratory tract secretions.

DESIGN

We performed a retrospective study of adult patients admitted to a large urban hospital. Patients had a nasal MRSA PCR test and a lower respiratory tract culture obtained within 48 hours of admission and the culture yielded S aureus.

MAIN OUTCOME MEASURES: Sensitivity, specificity, and positive and negative predictive values.

RESULTS

Our results showed high sensitivity (93.3%) and negative predictive value (95.2%) of nasal PCR for MRSA in the lower respiratory tract.

CONCLUSION

With its high sensitivity and negative predictive value, a nasal MRSA PCR test performed within 48 hours of hospital admission could help guide the discontinuation of MRSA-directed empiric antibiotic therapy in patients who are unlikely to be infected with this organism. A prospective study is needed to confirm these findings.