Nasal carriage of Staphylococcus aureus on admission to intensive care: incidence and prognostic significance

We retrospectively studied the prevalence of the nasal carriage of methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) on admission to a medical surgical intensive care unit (ICU). We also compared the intensive care survival of MSSA carriers with non-carriers. Records of 678 patients admitted over a 24-month period were retrospectively reviewed. Nasal swabs were taken from 565 patients on admission to the ICU. MSSA was isolated from the anterior nares of 126 (22%) patients, MRSA was isolated in 16 (3%) patients and 423 (75%) patients had no nasal carriage identified. MSSA carriers were more likely to have been admitted to the ICU after less than 24 h hospital stay (28% non-carriers, 44% MSSA carriers) and were significantly younger (mean age of 50 years) than non-carriers (mean age 55 years). The median survival (with confidence intervals (CI)) was 29 days (CI 14–44) in non-carriers, 16 days (CI 10–22) in MSSA carriers and 6 days (CI 4–8) for the MRSA carriers. This difference was significant when MSSA carriers were compared with non-carriers (p=0.003). The ICU mortality was also significantly higher (p=0.004) in MSSA carriers (88 of the 423 (21%) non-carriers and 40 of 126 (32%) MSSA carriers died prior to ICU discharge).