Ocular microbiology trends in Edmonton, Alberta: a 10-year review

Methicillin-resistant Staphylococcus aureus (MRSA) has been recognized as an increasingly common cause of nosocomial infections since the 1980s.(1) Reports of ocular infections due to MRSA are composed primarily of case reports. But a recent report from the United States suggests that ocular infections due to MRSA are about to become more common than methicillin-sensitive S. aureus (MSSA).(2) However, this observation is not consistent with anecdotal experience at the University of Alberta. The purpose of this study is to evaluate the ocular microbiology trends in a tertiary care eye center in Canada.

Cross-sectional study using a computer search of the DynaLIFE(DX) Diagnostic Laboratory Services database for all positive ocular microbiology cultures and in vitro antibiotic susceptibilities performed in the Edmonton area.

Over a 10-year period, between 2000 and 2010, 6.4% of S. aureus isolates were MRSA; there were 2030 MSSA and 129 MRSA isolates, including 46 MSSA and 4 MRSA isolates from deep eye cultures. The prevalence of MRSA over the total number of S. aureus isolates, regardless of specimen source, steadily increased in the 10-year period, from 0.5% in 2002 to 12.6% in 2010. Gram-positive cocci were the most common organisms to cause ocular infections (82.6%). In vitro susceptibility of ocular MSSA and MRSA samples demonstrated 100% sensitivity to vancomycin.

The prevalence of MRSA ocular infections, although still uncommon, appears to be increasing in Edmonton, Alberta.