Virulence characteristics and molecular relatedness of methicillin resistant Staphylococcus aureus harboring...

Methicillin resistant Staphylococcus aureus (MRSA) is a versatile pathogen capable of causing multitude of human diseases. It is one of the most important nosocomial pathogen that implicated in community and healthcare associated infections. Therefore, this study aims to characterize different SCCmec elements found in MRSA isolates. Moreover, molecular typing was performed to investigate the genetic relatedness among MRSA isolates.

Phenotypic identification of MRSA was done by disc diffusion method. The MRSA isolates were typed based on the SCCmec, coa and agr genes. Phenotypic characterization included the detection of biofilm, lipase, protease, lecithinase, staphylokinase and hemagglutination. Also, hla, hlb, hlg, hld, tsst-1, psm-mec and mecI genes were detected genotypically. The correlation between the molecular types identified and the profile of virulence factors, clinical and geographical sources was determined for all isolates.

Eighty five isolates were identified as MRSA. Eight types of SCCmec elements were detected among these isolates. Type V was the most observed type (56.47%). Regarding the correlation between SCCmec types and virulence factors, type V SCCmec exhibited a significant association with biofilm (p < 0.0001), staphylokinase (p = 0.0495) and tsst-1 (p = 0.0498). Molecular typing of coa gave an insight to the presence of specific types in specific hospital wards. Based on agr typing, agr I was the highest prevalent type in MRSA isolates (54.11%).

There is an increase of MRSA infections particularly the community acquired with high variability in the distribution of virulence factors among different SCCmec types. The association between type III and V SCCmec with certain hospitals may be an evidence of nosocomial infection among these hospitals.