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The following is a summary of “Utility of MRSA nares PCR for non-respiratory cultures in critically ill patients: an observational evaluation,” published in the December 2024 issue of Infectious Disease by Rodriguez et al. 

Antibiotic overuse can lead to resistance and adverse events, while negative Methicillin-resistant Staphylococcus aureus (MRSA) nares polymerase chain reaction (PCR) may streamline therapy for respiratory infections due to high negative predictive value (NPV) (95-99%). Although high NPV is reported for non-respiratory cultures, its use in patients with critical illness for guiding antibiotic therapy remains uninvestigated.  

Researchers conducted a retrospective study to assess the clinical utility of MRSA nares PCR in non-respiratory cultures among patients with critical illness.  

They evaluated the clinical utility of MRSA nares PCR in patients with critical illness. The outcomes assessed included NPV, positive predictive value (PPV), sensitivity, and specificity of MRSA nares PCR. A subgroup analysis based on the site of culture (blood, urine, and wound) was also performed.  

The results showed that of 325 patients screened, 200 patients with critical illness were included for analysis. A total of 259 cultures were assessed, with blood being the most frequent source (n = 124). The MRSA nares PCR was positive in 34 (17%) patients, and 13 (5%) of the 259 cultures tested positive for MRSA. Overall, MRSA nares PCR yielded an NPV of 99%, a PPV of 28%, a sensitivity of 77%, and a specificity of 85%. The subgroup analysis for different culture types showed similar results.  

Investigators concluded that a negative MRSA nares PCR may be a valuable tool to guide the initiation or de-escalation of anti-MRSA antibiotics in patients with critical illness when clinically appropriate. 

Source: tandfonline.com/doi/full/10.1080/23744235.2024.2438822