Session:

Bacterial Infections

Abstract No.:

45.046

Title:

Genetic diversity of Malaysian methicillin resistant Staphylococcus aureus strains based on virulotypes, pulsed-field gel electrophoresis and PCR-RFLP of coa gene

Author(s):

K. T. Lim¹, Y. Abu Hanifah², M. Y. Mohd Yusof², K.-L. Thong³; ¹University of Malaya, Institute of Biological Science, Faculty of Science, Kuala Lumpur, WP/MY, ²University of Malya, Department of Medical Microbiology, Kuala Lumpur/MY, ³Institute of Biological Sciences, Laboratory of Biomedical Science and Molecular Microbiology, University of Malaya, Faculty of Science, Kuala Lumpur/MY

Abstract:

Background: Staphylococcus aureus is a persistent human pathogen responsible for a variety of infections ranging from soft-tissue infections to bacteremia. The objective of this study was to determine the prevalence of a repertoire of toxin genes among Malaysian MRSA strains isolated over a four years period and the genetic relatedness of MRSA strains.
Methods: One hundred eighty-eight strains (2003, 2004, 2007 and 2008) of methicillin-resistant S. aureus (MRSA) isolated from a tertiary hospital were screened for 20 genes encoding for extracellular virulence determinant (sea, seb, sec, sed, see, seg, seh, sei, sej, tst, eta, etb,etd) and adhesins (cna, etb, fnbA, fnbB, hlg, ica, sdrE) via PCR. The genetic relatedness of these strains was determined by PFGE, PCR-RFLP of coa gene and agr grouping.
Results: Majority of the strains were tested positive for efb and fnbA (96% each), ica (78%) and hlg (59%) genes. A total of 101 strains were positive for at least one type of staphylococcal enterotoxin genes with sea being the predominant. Genes for seb, sed, see, seh, sej, eta and etb were not detected in any of the MRSA strains. The prevalence of sea, sec and ica among strains isolated in 2008 was increased significantly (p < 0.05) compared to 2003. Most of the strains were of agr type I (97.5%) followed by agr type II (1.2%) and agr type III (0.6%). Subtyping by PFGE and PCR-RFLP of coa gene produce 88 different pulsed-field profiles (F=0.51-1.0) and 47 different patterns (F=0.24-1.0), respectively.
Conclusion: No direct correlation between virulotypes, PFGE and PCR-RFLP profiles was observed. Strains with identical PFGE and PCR-RFLP profiles frequently belonged to different virulence patterns. Increase of MRSA strains with virulence factors over the years signal the potential loss of the usage of antimicrobial agents in treating MRSA infections as MRSA strains with virulence factors are normally resistant to host immune systems and other antimicrobial agents. The MRSA clinical strains from this tertiary hospital were genetically related, suggesting that few predominant clones of the species are involved in infections.