Prevalence, risk factors, and molecular epidemiology of methicillin-resistant Staphylococcus aureus nasal and axillary colonization among psychiatric patients on admission to an academic medical center.

BACKGROUND

Infection control data from psychiatric units and clinics are limited.

METHODS

This time series study was designed to determine the prevalence and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) colonization and/or infection among 500 men and women on admission to psychiatric units at The Johns Hopkins Hospital. Discharge surveillance was conducted to measure incidence. Molecular characterization was performed.

RESULTS

Five hundred subjects (52% male) were enrolled. The prevalence of MRSA colonization was 5.2% (26 of 498). Seven of 29 patients (24.1%) admitted with a skin and soft tissue infection (SSTI) was MRSA-positive; 4 of these patients had no other positive site, raising the total admission prevalence to 6.0%. A history of abscess (current or within the past 6 months) on admission (odds ratio [OR], 6.06; 95% confidence interval [CI], 2.40-15.31; P < .001), HIV infection (OR, 4.03; 95% CI, 1.52-10.71; P = .005), previous isolation (OR, 5.03; 95% CI, 1.76-14.35; P = .003), and unknown history of isolation (OR, 4.10; 95% CI, 1.41-11.98; P = .01) were associated with increased odds of MRSA colonization. Seven (2.6%) new MRSA colonizations were identified at discharge. Molecular analysis identified USA300 clonal MRSA isolates.

CONCLUSIONS

The prevalence of MRSA colonization in this study population was greater than reported in the general population. Further studies are needed to identify transmission dynamics in this environment.