Objective: To identify the rate and risk factors for asymptomatic nasal MRSA colonization, and evaluate the impact of a control program that depends on screening followed by application of contact isolation precautions on colonized patients, on the rate of invasive MRSA infection.
Methods: Screening all admissions was adopted as a hospital policy. Nasal samples were obtained for culture at admission from all patients for 18 months starting from January 2008. Laboratory culture results were monitored to identify all MRSA infections that occurred during the study period.
Results: Nasal swabs were collected by nurses with a 30% compliance with the screening policy during the first 6 months of the study, then by laboratory staff with 90% compliance. Of the 1350 patients who had cultures of nasal samples performed at admission, 7.7% were colonized with MRSA, and 15% were colonized with MSSA.
The risk factors for colonization were admission from ER (p=0.04), prior antibiotic therapy (p= 0.00), living with a MRSA patient (p= 0.00), being a healthcare worker (0.005) and contact with pets or animals (p= 0.00). The total incidence of MRSA infections was reduced from 0.3 to 0.1/1000 Pt D (66.6%), and from 1.6 to 0.4/ 1000 discharges (75%). Invasive MRSA infection rate was reduced from 0.21 to zero/1000 Pt D for 3 successive months. The ratio of MRSA to total S.aureus was reduced from 0.61 to 0.5.
Conclusions: The rate of nasal MRSA colonization at admission to the hospital was high compared to international reports. Most colonized patients showed risk factors for healthcare- associated MRSA. Few have contact with pets or animals. The hospital control program based on screening all patients on admission and applying contact precautions decreased the rates of total and invasive MRSA infections.