Background: Assessment of colonization by methicillin-resistant Staphylococcus aureus (MRSA) in hospitalized patients is essential to promptly institute isolation precautions and reduce transmission in healthcare institutions. Specimens are usually obtained from the nares, axillae, and groin. Recent literature suggests that the gastrointestinal tract may be an important site for MRSA colonization. However, the incremental yield afforded by rectal swabs or stool cultures is unclear.
Objective: To determine the yield of MRSA from surveillance specimens taken from the gastrointestinal tract compared with specimens obtained from the nares, using systematic review methodology.
Methods: We searched multiple computerized databases for studies that examined screening for MRSA by using both rectal and nares specimens in hospitalized patients. Results were pooled for summary estimates for sensitivity and specificity.
Results: Thirteen observational studies met inclusion criteria. Three were limited to the ICU, seven were either limited to inpatient units or combined ICU and non-ICU populations. One study was in liver transplant patients and one was in pregnant women. One did not mention the study population. Overall, 2265 patients with MRSA colonization or at high risk for MRSA colonization were included. The sensitivity of nasal specimens ranged from 60-80%. The sensitivity of rectal swabs or stool cultures ranged from 6-35%. Few studies examined the incremental yield of rectal swabs compared with nares specimens and found that rectal cultures yielded an additional 10-15% of MRSA carriers. Our analysis was limited by heterogeneity in the study population, differing culture media for detection of MRSA and variability in sampling frequency.
Conclusions: Our analysis shows that the gastrointestinal tract may be an important site for MRSA carriage. Whether gastrointestinal colonization leads to a higher risk of infection compared with nasal colonization needs further study.