High prevalence of carriage of methicillin-resistant Staphylococcus aureus at hospital admission in elderly patients: implications for infection control strategies.

BACKGROUND

Despite contact isolation precautions for patients with methicillin-resistant Staphylococcus aureus (MRSA), MRSA infections are increasing in many countries.

OBJECTIVE

To evaluate the role of a potential unrecognized reservoir of MRSA carried by patients in acute care wards, we determined the prevalence of MRSA at hospital admission, with special emphasis on screening-specimen yields.

SETTING

A 1100-bed teaching hospital in Paris, France.

METHODS

Nasal screening cultures were performed at admission to a tertiary-care teaching hospital for patients older than 75 years.

RESULTS

MRSA was isolated from 63 (7.9%) of 797 patients. On the multivariate analysis, variables significantly associated with MRSA carriage were presence of chronic skin lesions (adjusted odds ratio [AOR], 5.10; 95% confidence interval [CI95], 2.52-10.33); transfer from a nursing home, rehabilitation unit, or long-term-care unit (AOR, 4.52; CI95, 2.23-9.18); and poor chronic health status (AOR, 1.80; CI95, 1.02-3.18). Without admission screening, 84.1% of MRSA carriers would have been missed at hospital admission and 76.2% during their hospital stay. Furthermore, 81.1% of days at risk for MRSA dissemination would have been spent without contact isolation precautions had admission screening not been performed.

CONCLUSIONS

MRSA carriage at hospital admission is far more prevalent than MRSA-positive clinical specimens. This may contribute to failure of contact isolation programs. Screening cultures at admission help to identify the reservoir of unknown MRSA patients.