Community-Acquired MRSA Study

Community-Acquired MRSA Study

Seybold U, Halvosa JS, White N, et al. Emergence of and Risk Factors for Methicillin- Resistant Staphylococcus aureus of Community Origin in Intensive Care Nurseries. Pediatrics 2008; 122:1039–1046. [Full text] [PDF]

Objective. The goal of this study was to define more clearly the impact of community- acquired methicillin-resistant Staphylococcus aureus (MRSA) clones (e.g., USA300 and USA400) on colonization and infection in infants in intensive care nurseries and potential modes of transmission of community-acquired MRSA clones.

Methods. Prospective surveillance for MRSA colonization and infection was performed among infants in the intensive care nurseries at Grady Memorial Hospital (Atlanta, GA) between 1993 and 2006. Beginning in September 2004, nares surveillance cultures were collected at admission. MRSA isolates were genotyped by using pulsed-field gel electrophoresis and multiplex polymerase chain reaction assays for staphylococcal chromosomal cassette mec gene complex type and Panton-Valentine leukocidin genes. Prevalence of and risk factors for colonization with community-acquired versus health care-associated MRSA (e.g., USA100) were assessed.

Results. Between 1993 and 2006, 130 (3.5%) of 3707 infants were identified to be colonized with MRSA. Twelve (1.2%) of 996 admission nares cultures were positive for MRSA (since initiation of admission cultures in September 2004). Community-acquired MRSA clones were first recovered in 1998; the proportion of MRSA clones of community origin increased significantly between 1998 and 2004. Multivariate analysis identified vaginal delivery and maternal smoking, both among infants of mothers receiving systemic antibiotic treatment before delivery, as independent predictors for neonatal colonization with community-acquired MRSA. Systemic antibiotic therapy before delivery for nonsmoking mothers delivering through cesarean section and possibly endotracheal intubation were associated with the recovery of health care-associated MRSA clones.

Conclusions. Community-acquired MRSA clones have emerged as a major cause of MRSA colonization in high-risk newborns. Community-acquired MRSA recovery was associated with acquisition during birth, whereas health care-associated MRSA clones seemed to be transmitted nosocomially.

Comments. This study shows that community acquired MRSA seems to be vertically transmitted and is associated with maternal factors such as vaginal delivery and maternal smoking. Hospital acquired MRSA is more commonly associated with infant related factors such as comorbidity and medical treatment. DB

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