Molecular Analysis and Genotyping of Methicillin‑Resistant <i>Staphylococcus aureus</i> Strains Isolated from Different Clinical Sources

Abstract

Background: Investigating genetic relatedness between methicillin‑resistant Staphylococcus aureus (MRSA) strains from humans and different animal species may clarify the epidemiological characteristic of MRSA infections together.

Aim: The aim of the study was to perform genotypic characterization and type strains of MRSA isolated from different clinical sources, by molecular techniques.

Materials and Methods: The molecular characterization of the strains was performed by polymerase chain reaction (PCR), using several specific oligonucleotides. These were as follows: S. aureus species‑specific sau gene, mecA gene coding PBP2a responsible for methicillin resistance, femA gene coding for a protein, which influences the level of methicillin resistance of S. aureus, and is universally present in all MRSA strains; spa gene coding for protein A; coa gene coding for coagulase, and blaZ gene coding for the production of beta‑lactamase. To determine the genetic diversity of these strains, random amplified  polymorphic DNA–polymerase chain reaction (RAPD‑PCR) was performed.

Results: Among the 415 S. aureus strains, 61 were phenotypically  identified as MRSA, and confirmed as S. aureus by amplification of sau gene. However, 90.16% of the strains were mecA positive, while all were negative for femA gene. The presence and polymorphism of coa and spa genes were investigated and 83.60% and 18.03% strains were positive for coa and spa, respectively. While these strains were grouped into six coa‑types by PCR, no polymorphism was found for spa gene among strains having only single 190 bp of the band. bla genes were found in 75.40% of strains. These strains were divided into 12 RAPD types.

Conclusions: The  results showed the relatively high heterogeneity and variation of coa gene among MRSA strains, while further studies on sequencing of these strains may identify which sequence type is predominant in this region.

Keywords: Methicillin‑resistant Staphylococcus aureus, molecular typing, RAPD, virulence genes