Colonization and infection with antibiotic-resistant bacteria in a long-term care facility.

OBJECTIVE: To assess colonization and infection with methicillin-resistant Staphylococcus aureus (MRSA), high-level gentamicin-resistant enterococci (R-ENT) and gentamicin and/or ceftriaxone-resistant Gram-negative bacilli (R-GNB) and the factors that are associated with colonization and infection with these organisms.

DESIGN: Monthly surveillance for colonization and infection over a period of 2 years. In the second year, an intervention to decrease MRSA colonization by the use of mupirocin ointment was carried out.

SETTING: Long-term care facility attached to an acute care Veterans Affairs Medical Center.

PATIENTS: A total of 551 patients in the facility were followed for a period of 2 years.

MEASUREMENTS: Colonization and infection rates with MRSA, R-ENT, and R-GNB. Analysis of risk factors associated with colonization and infection with these three groups of organisms.

MAIN RESULTS: In the first year, colonization rates were highest for MRSA (22.7 +/- 1% patients colonized each month) and R-ENT (20.2 +/- 1%) and lower for R-GNB (12.6 +/- 1%). After introduction of decolonization of nares and wounds with mupirocin, the rate of MRSA colonization fell significantly to 11.5 +/- 1.8%, but rates remained unchanged for R-ENT and R-GNB. Risk factors for MRSA colonization included the presence of wounds and decubitus ulcers. For R-ENT, the presence of wounds, renal failure, intermittent urethral catheterization, low serum albumin, and poor functional level were significant. For R-GNB, intermittent urethral catheterization, chronic renal disease, inflammatory bowel disease, presence of wounds, and prior pneumonia were significantly associated with colonization. Overall, of infections caused by known organisms, 49.6% were due to MRSA, R-ENT, or R-GNB, and 50.4% were due to susceptible organisms. Infections were more commonly due to R-GNB (21.1% of all infections) than to R-ENT (8.3%) or MRSA (4.6%). The most common infections were urinary tract infections (42.9% of all infections) and skin and soft tissue infections (31.9% of all infections). Risk factors for MRSA infections were diabetes mellitus and peripheral vascular disease, for R-GNB infections were intermittent urethral catheterization and indwelling urethral catheters, and no one factor was associated with R-ENT infection.

CONCLUSIONS: In our long-term care facility, colonization with resistant MRSA and R-ENT was more common than R-GNB, but infections were more often due to R-GNB than R-ENT and MRSA. Several host factors, which potentially could be modified in order to prevent infections, emerged as important in colonization and infection with these antibiotic-resistant organisms.