Genetic diversity of Staphylococcus aureus in Lebanon. (c2012)

Abstract

Staphylococcus aureus, one of the most significant human pathogens, causes different infections ranging in severity from mild superficial skin infections to life threatening bacteremia and endocarditis. The occurrence and dissemination of methicillin-resistant variants (MRSAs) in clinical settings has raised the concern for the constant increase of nosocomial infections all over the world. Additionally, the appearance of MRSA among the community (community acquired [CA-MRSA]) and its risk of being introduced into hospitals is a matter of great concern. Effective epidemiological studies based on typing are indispensible for confirming the genetic relatedness of closely related isolates belonging to the same clonal lineages as well as for screening and controlling the occurrence and spread of epidemic clones in the region. This study aimed at the molecular characterization of S. aureus in Lebanon. 132 S. aureus isolates, 39 MRSA and 93 Methicillin-susceptible (MSSA), were collected from the American University of Beirut Medical Center (AUB-MC) and were characterized using different typing methods including S. aureus protein A (spa) typing, staphylococcal chromosomal cassette (SCCmec) typing of MRSA, multilocus sequence typing (MLST) and Pulsed-Field Gel Electrophoresis (PFGE). The detection of Panton-Valentine Leukocidin (PVL) and the distribution of SCCmec types I-VIII were performed by multiplex PCR assays. PVL were detected in 54% of MRSA and 12% of MSSA. Seventy one different spa types were identified and clustered into 40 groups with the most common spa type being t044 (13%) among MRSA and t021 (8%) among MSSA. SCCmec typing showed the prevalence of types IV (d, e, f, g, and h) (49%) followed by IVa (31%), V (13%), IVc (5%) and III (3%). Twenty five allelic profiles or STs were identified by MLST with the major STs being ST80 (11%) and ST30 (8%). PFGE revealed 32 groups by applying 80% as a cutoff similarity. Clustering mec typing with MLST revealed that ST80-MRSA-IV and ST30-MSSA were the predominant clones in Lebanon. The present study showed the great diversity between MRSA and MSSA isolates in Lebanon compared to previous conducted studies. Systematic surveillance is required for isolates associated with both hospital- and community-acquired infections to limit and control the spread of S. aureus. Future studies with larger number of samples from different countries are essential in order to better assess and characterize MRSA and MSSA in the region. Determining the prevailing genetic populations in Lebanon along with their prevalence in causing diseases will help in developing measures to control the spread of these potentially serious infections.