464. Fecal Staphylococcus aureus in the Neonatal Intensive Care Unit

Abstract

Background Staphylococcus aureus colonization in infants in the neonatal intensive care unit (NICU) often leads to repeated infections and severe disease. Methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) infections are major causes of NICU outbreaks. Current national practice in NICUs utilizes nare swab surveillance for S. aureus. We hypothesize that infants colonized in the stool with S. aureus may go unrecognized particularly when nare swab negative, allowing for a transmission reservoir. While it is unclear why some S. aureus nare carriers are also stool colonized, isolates tend to have clonality. A true prevalence of S. aureus fecal carriage is not well understood and variable.MethodsAvailable stool samples were prospectively collected from 42 of 55 infants admitted in a level IV NICU on a single day, per Cincinnati Children’s institutional review board approval. Nare swab results were obtained from electronic medical records. DNA was isolated from stool and shotgun metagenomic sequencing was performed via Hiseq Illuminex 2500. The presence of S. aureus and MRSA were defined as having >100 sequencing reads and a mecA DNA read fraction ratio >40 per stool sample, respectively.ResultsOf the 42 stool samples sequenced, 33 were S. aureus (15 MSSA, 18 MRSA) positive. All infants with nare positive MSSA (n = 9) were colonized in the stool with a 93% and 100% sensitivity and specificity, respectively. While infants with nare positive MRSA (n = 10) were stool colonized with 100% and 83% sensitivity and specificity, respectively. Three nare positive infants with MRSA had S.a. in the stool but lacked the presence of mecA. When comparing clinical nare swabs to stool metagenomic surveillance, sensitivities were 60% for MSSA and 56% for MRSA.ConclusionInfant colonization of S. aureus in the NICU remains a major problem despite current national surveillance and isolation practices. We found that nare swab surveillance for S. aureus in infants significantly underestimated colonization rates when compared with shotgun metagenomics of stool. These results suggest that nare swabs alone may not have adequate sensitivity and the implementation of stool surveillance should be considered to augment current practices. Future study is necessary to understand how the S. aureus stool reservoir contributes to transmissionDisclosures All authors: No reported disclosures.