Risk Factors for Colonization with Methicillin-Resistant Staphylococcus aureus (MRSA) in Patients Admitted to an Urban Hospital: Emergence of Community-Associated MRSA Nasal Carriage

• Published in: Clinical infectious diseases Vol. 41; no. 2; pp. 159 - 166
• Main Authors: Hidron, Alicia I., Kourbatova, Ekaterina V., Halvosa, J. Sue, Terrell, Bianca J., McDougal, Linda K., Tenover, Fred C., Blumberg, Henry M., King, Mark D.
• Format: Journal Article
• Language: English
• Published: United States The University of Chicago Press 15.07.2005; University of Chicago Press; Oxford University Press
• Subjects: Adolescent; Adult; Antimicrobials; Bacteria; Case-Control Studies; Community-Acquired Infections - diagnosis; Cross Infection - epidemiology; Cross Infection - microbiology; Female; Genotypes; HIV infections; Hospital admissions; Hospitals; Humans; Infections; Infectious diseases; Major Articles; Male; Methicillin Resistance; Methicillin resistant staphylococcus aureus; Microbial colonization; Middle Aged; Multivariate Analysis; Nose - microbiology; Odds Ratio; Operating rooms; Penicillin; Predisposing factors; Prevalence; Risk Factors; Skin; Staphylococcal Infections - epidemiology; Staphylococcal Infections - microbiology; Staphylococcus aureus; Staphylococcus aureus - drug effects
• ISSN: 1058-4838; 1537-6591
• DOI: 10.1086/430910

Background. Surveillance cultures performed at hospital admission have been recommended to identify patients colonized with methicillin-resistant Staphylococcus aureus (MRSA) but require substantial resources. We determined the prevalence of and risk factors for MRSA colonization at the time of hospital admission among patients cared for at a public urban hospital. Methods. Anterior nares cultures were obtained within 48 h after admission during a 1-month period. A case-control study and molecular typing studies were performed. Results. A total of 53 (7.3%) of 726 patients had a nares culture positive for MRSA, and 119 (16.4%) had a nares culture that was positive for methicillin-susceptible S. aureus. In multivariate analysis, risk factors for MRSA colonization included antibiotic use within 3 months before admission (odds ratio [OR], 2.5; 95% confidence interval [CI], 1.2–5.0), hospitalization during the past 12 months (OR, 4.0; 95% CI, 2.0–8.2), diagnosis of skin or soft-tissue infection at admission (OR, 3.4; 95% CI, 1.5–7.9), and HIV infection. A total of 47 (89%) of 53 case patients colonized with MRSA had at least 1 of these independent risk factors, in contrast to 343 (51%) of 673 control patients (OR, 7.5; 95% CI, 3.2 –17.9). Molecular typing demonstrated that 16 (30%) of 53 MRSA nares isolates (2.2% of the 726 isolates) belonged to the USA300 community-associated MRSA (CA-MRSA) genotype. Conclusion. The prevalence of MRSA colonization at the time of patient admission was high (>7%). Limiting surveillance cultures to patients with ⩾1 of the identified risk factors may allow for targeted screening. The emergence of CA-MRSA colonization represents a new, unrecognized reservoir of MRSA within hospitals, potentially increasing the risk for horizontal transmission.