Carriage rates of methicillin-resistant Staphylococcus aureus (MRSA) depend on anatomic location, the number of sites cultured, culture methods, and the distribution of clonotypes

• Published in: European journal of clinical microbiology & infectious diseases 2010-12, Vol.29 (12), p.1553-1559
• Main Authors: Lauderdale, T.-L. Y., Wang, J.-T., Lee, W.-S., Huang, J.-H., McDonald, L. C., Huang, I.-W., Chang, S.-C.
• Format: Article
• Language: English
• Subjects: Axilla - microbiology; Bacterial diseases; Bacteriological Techniques; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Carrier State - epidemiology; Carrier State - microbiology; Colonization; Culture Media; Hospitals; Hospitals, Urban; Human bacterial diseases; Humans; Infectious diseases; Intensive care; Intensive Care Units; Internal Medicine; Laboratories; Medical Microbiology; Medical research; Medical sciences; Methicillin-Resistant Staphylococcus aureus - classification; Methicillin-Resistant Staphylococcus aureus - genetics; Methicillin-Resistant Staphylococcus aureus - isolation & purification; Nasal Cavity - microbiology; Nosocomial infection; Nosocomial infections; Patients; Perineum - microbiology; Pharynx - microbiology; Population Surveillance - methods; Research centers; Sputum - microbiology; Staphylococcal Infections - epidemiology; Staphylococcal Infections - microbiology; Staphylococcal infections, streptococcal infections, pneumococcal infections; Staphylococcus aureus; Staphylococcus infections; Taiwan - epidemiology
• ISSN: 0934-9723; 1435-4373
• DOI: 10.1007/s10096-010-1042-8

The present study was carried out to determine how active surveillance for methicillin-resistant Staphylococcus aureus (MRSA) could be improved by the use of enrichment broth and the inclusion of extra-nasal sites with nares cultures. Molecular typing was also performed to identify colonization by single or multiple strains. Surveillance cultures for MRSA were obtained from 650 patients on admission to a medical and surgical intensive care unit (ICU) in Taiwan. MRSA was detected on directly plated vs. broth-enrichment cultures in any site at 10.0% vs. 24.2%, nares 8.2% vs. 17.5%, throat 4.8% vs. 13.4%, axilla 1.2% vs. 9.1%, and perineum 1.8% vs. 9.5%, respectively. Nares cultures alone detected only 81.5% and 72.5% of all colonized patients by direct and broth-enriched cultures, respectively. The molecular typing of 68 isolates from 17 patients revealed that multisite isolates were largely indistinguishable within each patient, but four patients had multiple subtypes and another three patients had different clonotypes. The detection of MRSA carriers was considerably enhanced by broth-enrichment cultures at multiple anatomic sites and simultaneous colonization by multiple strains at different sites can occur. Epidemiological studies are needed to determine the likelihood of subsequent nosocomial infection among colonized patients detected via direct nasal versus broth-enriched cultures from multiple sites.