Geographic Cluster of Community-Acquired Methicillin-Resistant Staphylococcus aureus Infections Among Pediatric Patients From Brooklyn, New York

Abstract

Background. We have recently observed an increase in community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections among pediatric patients from Brooklyn hospitalized at a university-based teaching hospital in New York City. We performed a prospective study to determine the colonization prevalence of CA-MRSA among hospital admission, genome sequence strains causing infection and identified risk factors associated with CA-MRSA carriage in this population. Methods. Colonization data were obtained from routine infection control screening upon admission to the general pediatric and intensive care units. We used a questionnaire to identify risk factors for MRSA transmission. Additionally, single patient isolates of CA-MRSA were collected from the clinical microbiology laboratory. Medical record information was used to ascertain patient infection or colonization and to confirm community onset. Children from high-risk communities were identified via zip codes. Figure. Phylogenetic tree of clinical MRSA USA300 isolates from children living in high-risk zip codes (red), adult and pediatric patients at NYU Tisch Hospital (Blue), and USA300 Strains from around the United States (Green; Pfizer). Results. Children from the high-risk zip codes were 3 times as likely to be colonized with MRSA (9% versus 3% [p = 0.04]). No difference in methicillin-susceptible S. aureus colonization prevalence was observed between children from high-risk and low-risk communities. Likewise, the MRSA infection rate per 1000 patient days was 36 for children from high-risk zip codes, and 3.9 in children from low-risk zip codes (p < 0.0001). All isolates from patients in high risk zip codes analyzed to date belong to genotype USA300, the predominant CA-MRSA clone in the United States. Phylogenetic analyses suggest that these strains arose from expansion of an USA300 CAMRSA subclone. Potential risk factors for MRSA infection are being explored in conjunction with public health and community leaders. Conclusion. We identified a cluster of CA-MRSA strain USA300 among pediatric patients in a high risk Brooklyn community. Additional genomic comparisons and epidemiological data will be used to inform interventions and interrupt transmission. (Figure Presented) .