Objective: The purpose of this study is to examine the epidemiology and outcome of infections caused by S. aureus in Lebanon.
Methods: This is a retrospective case-case-control study from January 2000 to December 2008. The first group of cases consists of patients infected with MRSA strains, while the second group of cases consists of patients infected with methicillin-susceptible S. aureus (MSSA) strains matched to the site of infection. Cases were identified based on positive clinical cultures from the microbiology laboratory. The control group consists of patients admitted during the same period of time as the cases but who did not develop infections during their stay. Two multivariable models were performed: the first comparing the MRSA group to uninfected controls, and the second comparing the MSSA group to uninfected controls.
Results: A total of 174 patients were included in the study (58 MRSA cases, 58 MSSA cases, and 58 uninfected controls). The most common type of infection was skin and skin structure infections in 68 cases, followed by respiratory infections in 38 cases. Infections were considered community-acquired in 49% of cases, and hospital or healthcare-associated in 51% of cases (no differences between the MRSA and MSSA groups). In the first multivariable model (MSSA vs. uninfected controls), hospital stay within 30 days of the current episode was an independent predictor of infection (OR 3.5; 95% CI 1.4-9.3). In the second multivariable model (MRSA vs. uninfected controls), prior diagnosis of diabetes mellitus was associated with a higher risk of infection (OR 8.3; 95% CI 1.8-38.4). A total of 14 patients had a fatal outcome (7 in each of MRSA and MSSA groups). Mortality was deemed attributable to infection in 2 MSSA cases.
Conclusions: Diabetes mellitus seems to be a risk factor unique to MRSA infections. Recent antibiotic use was not associated with increased risk of infection. The outcome of MRSA infections does not seem to be worse than that of MSSA infections.