Community-Associated and Health care-Associated Methicillin-Resistant Staphylococcus aureus in Children: A Microbiological and Epidemiological Study

Abstract

Aims: Novel methicillin-resistant Staphylococcus aureus have been causing infections in the community and are now invading hospitals. In this study we aimed to determine, using epidemiological and microbiological parameters, the characteristics of circulating S. aureus clinical isolates. Methods: From July 2009 to April 2012, S. aureus isolates from children hospitalized in Santa Casa de São Paulo, a tertiary care-center in São Paulo, Brazil, were included.  All isolates grew in cultures from sterile sites and we included only one isolate per patient. Results: Fifty-five isolates were included during the study period, 47 from blood, six from abscesses, one from pleural fluid and one from spinal fluid. Among these isolates, 34 were methicillin susceptible S. aureus (MSSA) and 21 were methicillin-resistant S. aureus (MRSA). Eleven patients were excluded (5 MSSA and 6 MRSA) because clinical charts were not available for review, reducing the total to 29 MSSA and 15 MRSA isolates.  After searching for risk factor for healthcare-associated infections, 11 of the 15 MRSA isolates were epidemiologically considered health care-associated MRSA (HCA-MRSA) and 4 community-associated MRSA (CA-MRSA). Using the microbiological classification (multiresistance), five were considered as HCA-MRSA and 10 were CA-MRSA. Interestingly, of the 11 isolates considered as epidemiological HCA-MRSA (presence of any risk factor), six had a microbiological profile (non-multiresistant) consistent with CA-MRSA circulating clones.  Conclusion: Our results clearly show that the boundaries between CA-MRSA and HCA- are increasingly difficult to determine