SPA & MLST typing as epidemiological tools for the study of MRSA & MSSA Isolates in Lebanon. (c2009)

Abstract

Stapfylococt'UJ aureUJ, whether methicillin resistant (MRSA) or susceptible (MSSA), remains major causative agents of nosocomial and other infections with substantial morbidity and mortality worldwide. Molecular characterization of MRSA is important aspect for monitoring and controlling the current and emerging strains in different geographic locations. S. aureUJ typing has become an important tool in the study of strain origin, clonal relatedness and epidemiology of outbreaks. Protein A is a cell wall linked protein of S. aureUJ and the X region of the protein A gene (jpa) consists of direct repeats exhibiting an extensive polymorphism. Sequencing of the repeat region of the protein A gene generates informative typing results. The Jpa region consists of a variable number of 21-27 bp long repeats that differ in the nucleotide composition that result in different jpa types. BURP grouping algorithm (Based Upon Repeat Patterns) is commonly used to cluster jpa types by exclusion of Jpa types that are shorter than "x" repeats and the maximum number of costs "y" for clustering jpa types into the same group, with the calculated cost between members of the group being less than or equal to 4. Typing of 130 MSSA and MRSA isolates revealed the presence of 28 different spa types within the MSSA compared to 27 in the MRSA. Jpa types were clustered in this study into 23 different groups, with 11 groups comprising more than one jpa type and 12 so-called "singletons". It is noteworthy that a new novel repeat was detected in this study and was designated as jpa t4099. Multi-locus sequence typing (MLST) analysis was conducted on 11 reference strains corresponding to the most frequently occurring jpa types in both MSSA and MRSA. The most occurring MLST type was ST80- MRSA-IVc, accounting for 53.7% of all isolates. Other clones collected from our samples included ST239, ST8, ST30, ST5, ST22, and ST1. The relatively diverse range of genotypes, resulting from MLST, from a small country may reflect the importance of different genotypes being imported from distant countries. The results of this study indicate that Jpa typing, together with BURP clustering, MLST, and eBURST is a useful tool in S. aureus epidemiology, especially because of ease of use and the advantages of unambiguous sequence analysis as well as reproducibility and exchange of typing data. Accordingly, we recommend that large MSSA population studies should be conducted in parallel with MRSA surveillance studies, to better understand how populations of MSSA and MRSA co-evolve and interact.