Epidemiologic Similarities in Pediatric Community-Associated Methicillin-Resistant and Methicillin-Sensitive Staphylococcus aureus in the San Francisco Bay Area

Among children, as in adults, the reported numbers and proportion of methicillin-resistant Staphylococcus aureus (MRSA) compared to methicillin-sensitive S aureus infections (MSSA) have dramatically increased [1, 2]. MRSA was previously associated with healthcare risk factors such as recent hospitalization or surgery or presence of an indwelling catheter, but it has emerged in the community among previously healthy individuals without such risk factors [3]. This change in epidemiology has necessitated changes in treatment practices and burdened healthcare resources, not only due to high numbers of skin and soft tissue infections [4], but also because of life-threatening, invasive disease [5]. Understanding the risk factors for community-associated MRSA (CA-MRSA) will help shape public health interventions. Among adults, CA-MRSA has been associated with risk factors including injection drug use [6], homelessness [7], incarceration, and visiting bars and raves [8]. Outbreaks have also occurred among athletes [9], military recruits [10], and men who have sex with men [11]. However, the risk factors for CA-MRSA versus CA-MSSA infections in children are unclear [12, 13]. Surveillance studies and reports from outbreaks suggest that children from low socioeconomic status or racial minority groups, such as black or African-Americans, Pacific Islanders, and Native Americans are at risk [14]. There is documentation of transmission in daycare centers [15], households [16], and sports teams [17]. However, these studies are subject to bias as they are mostly retrospective, with data limited to chart reviews or specific outbreaks. Recognizing that the dynamics of CA-MRSA transmission differ from those in healthcare settings, the Centers for Disease Control (CDC) developed the “Five Cs of CA-MRSA Transmission.” This conceptual model suggests that infection is related to (1) contact with infected or colonized persons; (2) cleanliness; (3) compromised skin integrity; (4) contaminated objects or surfaces; and (5) crowding. A sixth “C” refers to capsules, or prior antibiotic use [18]. A high prevalence of these risk factors has been identified among children with CA-MRSA [19], but a study examining the relationship between these potential risk factor categories and CA-MRSA versus CA-MSSA has not been documented. We performed a prospective case-comparison investigation among pediatric patients from three medical centers in the San Francisco Bay Area [20]. For patients with a positive S aureus culture, we performed a chart review to evaluate clinical and demographic factors, telephoned parents or guardians of subjects to administer an extensive interview evaluating the 6 “Cs” of potential risk factors, and genotyped isolates for strain characterization.