Molecular Typing of Methicillin Resistant Staphylococcus aureus using Coa Gene Polymerase Chain Reaction-Restriction Fragment Length Polymorphism: A Cross-sectional Study
Dr. B Appalaraju,
Professor and Head, Department of Microbiology, PSG Institute of Medical Sciences
and Research, Coimbatore, Tamil Nadu, India.
Introduction: Methicillin Resistant Staphylococcus aureus (MRSA) are the most important multidrug resistant pathogen of humans causing a wide array of infections. Polymorphic Coagulase gene (coa) could be targeted for specific typing of Staphylococcus aureus isolates. ‘Possible source’ can be identified and discriminated rapidly for control and prevention of Staphylococcus aureus infections especially in case of suspected outbreaks. Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) have high discriminatory power and enhanced reproducibility. Mutation and variation in number of short sequence repeats lead to distinct amplification of this region of coa gene by PCR. Deoxyribonucleic Acid (DNA) fragments of different sizes obtained by digestion with specific restriction enzymes like Arthrobacter luteus I (AluI) help to discriminate various types based on the patterns produced as a result of PCR-RFLP.
Aim: To determine molecular typing of MRSA by coa gene PCR-RFLP.
Materials and Methods: A cross-sectional study was done in the Department of Microbiology involving 150 clinical isolates of Staphylococcus aureus obtained from various clinical specimens. Genotypic identification of MRSA was done by detecting coa gene and mecA gene by PCR. Molecular typing of MRSA was done by coa gene PCR-RFLP.
Results: Coa gene PCR identified six Genotypic codes (Code I to Code VI) ranging from 300 bp-800 bp size. Restriction digestion of the amplicons of the coa gene by PCR-RFLP using the enzyme AluI provided 17 unique restriction patterns among MRSA isolates in toto. The predominant coa gene PCR Genotype code was “Type IV” which was 600 bp size and predominant RFLP fragment for Genotype code “Type IV” was RFLP Pattern ‘b’ (500 bp, 240 bp and 140 bp fragments) among the study population.
Conclusion: Genotype code ‘IV’ and RFLP pattern ‘b’ was found to be predominant coa gene type among MRSA in this study.