MRSA Nasal Swab Shows No Reduction in Vancomycin Use

A randomized trial published in Clinical Infectious Diseases found that methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) nasal swab testing had a high negative predictive value among intensive care unit (ICU) patients with suspected community-acquired pneumonia (CAP), but did not significantly reduce the duration of vancomycin use or 30-day mortality.

The Swab Testing to Optimize Pneumonia Treatment With Empiric Vancomycin (STOP-Vanc) trial evaluated whether adding MRSA nares PCR testing to usual care could help guide vancomycin de-escalation in critically ill adults. The authors noted that concern about MRSA as a cause of CAP frequently leads to empiric vancomycin coverage, while prospective randomized data in ICU patients have been limited.

The pragmatic, prospective, single-center, nonblinded trial randomized 277 adult ICU patients with suspected CAP 1:1 to usual care with or without MRSA nares PCR testing after ICU admission. The primary outcome was vancomycin-free hours alive within the first 7 days after enrollment. In the intervention arm, MRSA PCR nasal swab testing had a negative predictive value of 98.9%.

Vancomycin-free hours alive were 109.7 hours in the intervention arm and 105.7 hours in the control arm, for an adjusted difference of 4 hours (95% CI, −9.5 to 18.2; P=.458). Thirty-day all-cause mortality was 26% in the intervention group compared with 35% in the control group, and acute kidney injury, length of stay, ICU length of stay, antibiotic-free days alive, ventilator-free days, and receipt of alternative anti-MRSA antibiotics were similar between groups.

The authors concluded that, despite the high negative predictive value of MRSA PCR nasal swab testing in this critically ill population, the intervention did not decrease vancomycin duration or 30-day mortality among ICU patients with suspected CAP. They suggested that additional clinician education and antimicrobial stewardship interventions may be needed to reduce vancomycin use in this setting.

Sources: Freiberg JA, Qian ET, Nairon KG, et al. Swab testing to optimize pneumonia treatment with empiric vancomycin: a randomized controlled trial. Clin Infect Dis. 2026;ciag295. doi:10.1093/cid/ciag295