Nasal screening alone may be insufficient for MRSA detection

Researchers of a recently published study suggest that cultures of multiple body sites be obtained before ruling out methicillin-resistant Staphylococcus aureus colonization.

Leonard Mermel, DO, ScM, AM (Hon), and colleagues enrolled adult patients during 2007 and 2008 who had a previous diagnosis of methicillin-resistant Staphylococcus aureus (MRSA). Participants had MRSA-positive clinical cultures during their most recent hospitalization or during a hospitalization within 1 year prior to enrollment.

Medical records of patients with positive MRSA cultures were reviewed to assess risk factors for MRSA carriage, as well as current and past MRSA infection. Mean age of colonized patients was 55 years; 64% were male.

MRSA was confirmed from at least one body site in 53 of 60 adults; 75% had MRSA colonization at extranasal sites, according to the researchers.

Sensitivity and negative predictive values for cultures of nasal passages were 91% and 58%; 63% and 26% for the groin; 47% and 20% for the perineum; and 32% and 16% for the underarm, respectively.

Greater sensitivity was found with nasal passages when compared with the underarm, groin and perineum. However, the groin was more sensitive than the underarm.

The greatest yield from any two body sites were the nasal passages and groin — a combined sensitivity of 98% and negative predictive value of 88%, according to the researchers.

Reference:
Mermel L. J Clin Microbiol. doi:10.1128/JCM.02601-10.

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