Genomic Profiling of Methicillin Resistant Staphylococcus aureus (MRSA) Isolates by SCCmec-typing Assay to Explore Epidemiological Diversity in a Tertiary Healthcare Setting, South India

Abstract

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) has been known as an infectious pathogen worldwide since 1960. The epidemiological distribution of MRSA may have shifted due to outbreaks reported from several nations, making it more challenging to differentiate among CA-MRSA and HA-MRSA. It is currently important to develop a strain-based explanation for HA and CA-MRSA due to its distinct epidemiology, genetic profile, antibiogram, and quantifiable features. The study aimed to distinguish CA and HA-MRSA by Staphylococcal Cassette Chromosome mec (SCCmec) typing. Materials and Method: The study involved a total of 381 S. aureus isolates, which were processed in the department of Microbiology, JSS Hospital, Mysore. All isolates were confirmed as MRSA, initially by disk diffusion method using cefoxitin 30µg and oxacillin 1μg disk and later by using PCR technique for the detection of mecA-gene. All mecA-gene positive samples were amplified for SCCmec typing by multiplex PCR for detection of SCCmec type I, II, III, IVa, IVb, IVc, IVd, V and XI respectively. Results: PCR confirmed a total of 66% isolates as mecA-positive MRSA. Multiplex PCR method revealed only 53% isolates were SCCmec-typeable. The mainstream of the isolates belonged to SCCmec type IV (53.48%) and type V (44.18%), followed by type III (9.30%), type II (3%) and type I (1.16%) respectively. The study also demonstrated the presence of multiple SCCmec types in 10.46% of MRSA isolates. Staphylococcal cassette chromosome recombinase (ccr) typing determined only 43% of isolates were typeable. Conclusion: The study found that hospital-associated SCCmec type IV and type V were the most circulating strains in our healthcare setting. The research identified a few MRSA isolates with diverse SCCmec types. The presence of CA-MRSA infection in in-patients and HA-MRSA infection in out-patients were also recognised. The situation indicates the spreading of hospital-acquired strains into the community and vice versa, necessitating the molecular characterisation of MRSA isolates in order to administer the appropriate antibiotic medication.

Keywords

• ca-mrsa
• ha-mrsa
• sccmec typing
• ccr-typing
• multiplex pcr