In this episode, I’ll discuss whether a nasal MRSA screen is useful for choosing antibiotics in critically ill patients with an intraabdominal infection.
A recent multicenter, retrospective, cohort study looking at the performance of a nasal MRSA screen in predicting intraabdominal infection with MRSA was published in the journal Pharmacotherapy.
Out of 192 patients analyzed, 6 had an intraabdominal infection from MRSA. This is to be expected since MRSA is a rare pathogen in intraabdominal infections. Of the 6 that were positive, 4 demonstrated a positive nasal MRSA screen. Of the 186 patients who were negative for an MRSA IAI, 19 (10.2%) had a positive nasal MRSA screen.
This translates to a 17.4% positive predictive value, and a 98.8% negative predictive value of nasal MRSA screens in intraabdominal infection.
The authors concluded:
Among critically ill adult patients with IAIs, a negative nasal MRSA screen within 30 days may help to empirically exclude MRSA as a causative pathogen in IAI with a high level of certainty.
While not a prospective study, one important strength was that it examined the performance of nasal MRSA screening up to 30 days prior to the intra‐abdominal culture. This means that the study results could be used to support a de‐escalation of anti‐MRSA therapy based on older nasal MRSA screen tests, which could prevent the initiation of unnecessary therapy while waiting for screening results.
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