Sensitive detection of Staphylococcus aureus colonization is important for epidemiologic studies, infection control, and decolonization measures. We examined the sensitivity of nasal and pharyngeal sampling for S. aureus colonization in 331 children admitted to intensive care units. Pharyngeal screening was more sensitive than nasal screening (92.6% versus 63.1%, P < 0.0001).Health care-associated Staphylococcus aureus infections increase morbidity, mortality, and hospital costs. Patients with surgical site infections (SSIs) due to methicillin-susceptible S. aureus (MSSA) are 3.4 times as likely to die, experience median lengths of stay 9 days longer, and incur median hospital costs $23,000 greater than controls (7). Even more severe outcomes follow methicillin-resistant S. aureus (MRSA) infections (2, 3, 7).S. aureus carriage is a well-known risk factor for infection. The relative risk of SSI associated with nasal colonization, compared to no colonization, is as high as 8.1, while in nonsurgical patients the relative risk of infection ranges from 1.8 to 14.0 (11). National guidelines recommend mupirocin administration for patients undergoing cardiac surgical procedures in the absence of a documented lack of S. aureus nasal carriage (6).Although the nares have been considered the primary site of S. aureus colonization (23), recent studies in adults indicate that pharyngeal carriage may be equally or more common (4,5,(13)(14)(15)(16)(17). Studies of pediatric pharyngeal carriage have assessed small numbers of subjects, but most suggest pharyngeal carriage may be common in children (1,9,10,12,19,21). We determined the prevalence of pharyngeal carriage and compared the sensitivities of pharyngeal and nasal screening among children admitted to our hospital's intensive care units (ICUs).(Study findings were presented in part as a slide presentation at the 2008 Interscience Conference on Antimicrobial Agents and Chemotherapy/Infectious Diseases Society of America Annual Meeting.)The study population consisted of patients admitted to the neonatal, medical-surgical, or cardiac ICUs from February through May 2008. Patients Ͼ18 years of age or with conditions unsafe for pharyngeal swab collection, such as recent pharyngeal surgery, were excluded. The hospital's Committee on Clinical Investigation approved the study protocol.Active surveillance cultures (ASC) for detection of MRSA carriage were already routine for ICU patients on admission and weekly thereafter. Swabs were taken from the nares and occasionally other sites (e.g., umbilicus, axilla, or groin) but not the pharynx. Nasal and pharyngeal study specimens were obtained once from each subject, at the same time as routine admission MRSA ASC, using the BBL CultureSwab system (a rayon swab packaged with Stuart's transport medium [BD Diagnostic Systems]). One swab was rotated gently in both nostrils and another upon both tonsils. Specimen collection was performed by ICU nurses, who also collect routine ASC; training was provided to assure uniform collection. Because th...