Epidemiology of community-associated methicillin-resistant Staphylococcus aureus in San Francisco children

Abstract

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in children is increasing worldwide, yet limited prospective studies have assessed epidemiologic risk factors for CA-MRSA infection in children. Our aim is to describe the clinical and microbiological characteristics of and potential epidemiologic risk factors for pediatric CA-MRSA infection in San Francisco. S. aureus isolate information from subjects 0-18 years old were prospectively collected over 6 months. Demographics and clinical details were gathered for subjects by chart review. Patients and/or guardians were interviewed about underlying conditions and potential risk factors for CA-MRSA such as a) previous MRSA/skin or soft tissue infection (SSTI) in patient or household; b) direct or indirect exposure to healthcare setting (recent antibiotics, emergency room visits, chronic disease or healthcare worker in household); c) community exposures (daycare, team sports, history of homelessness/group home, injection drug use or incarceration). Among S. aureus isolates from 216 subjects, 180 isolates from 170 subjects had community-acquired SA, 85 (50%) of whom had CA-MRSA. 91% of CA-MRSA patients had a SSTI. CA-MRSA resistance to clindamycin and ciprofloxacin were 7.8% and 50% respectively. Compared to community-associated methicillin-sensitive Staphylococcus aureus (CA-MSSA) patients, a significantly higher proportion of CA-MRSA patients were African-American, a smaller proportion were Asian/Pacific Islander, and a larger proportion were hospitalized. Among deep SSTI, 60/62 (97%) were MRSA. Over 50% of CA-MRSA patients were < 4 years old. 97% of interviewed MRSA patients had at least one potential risk factor; 85% of whom had an exposure to healthcare setting, 47% had or lived with someone who had previous MRSA or SSTI; and 60% had a potential community exposure. Fifty percent had an underlying atopic condition. This pediatric population had a high prevalence of potential epidemiologic risk factors for CA-MRSA and underlying conditions. Future studies comparing exposures of patients with CA-MRSA to those with CA-MSSA are needed to determine if these exposures are unique to subjects with CA-MRSA in this population.