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Updated: Jan 30, 2026
Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus
Published on: September 5, 2013
Detection and molecular typing of methicillin-resistant Staphylococcus aureus from northeastern part of India
Deepshikha Bhowmik1, Shiela Chetri2, Deepjyoti Paul3
1Junior Research Fellow (Microbiology), Assam University, Silchar, Assam, India.
Background:
In Staphylococcus aureus, methicillin resistance is exhibited by modifications in penicillin-binding protein that minimises the binding affinity to beta-lactam antibiotics. The present study investigated the occurrence of methicillin-resistant S. aureus (MRSA) in community-acquired infections, that is, community-acquired MRSA (CA-MRSA) and in-hospital-acquired infections, that is, hospital-acquired MRSA (HA-MRSA) from Northeast India.
Methods:
A total of 197 consecutive non-duplicate isolates were collected from Silchar Medical College and Hospital and other private diagnostic laboratories. The isolates were confirmed to be S. aureus at our centre. All isolates were subjected to antibiotic susceptibility testing and were screened for methicillin resistance using cefoxitin disc test. All MRSA were subjected to Polymerase Chain Reaction (PCR) assay for detection of mecA and mecC genes. DNA fingerprinting was performed for determining clonal diversity.
Results:
Seventy-one isolates of 127 confirmed S. aureus were found to be methicillin resistant by screening test. mecA gene was detected in 43 isolates, and none of the isolates were positive for mecC gene. Linezolid and teicoplanin showed better activity with susceptibility pattern being 83.6% and 72.44%, respectively, whereas 66.14% were sensitive to vancomycin. Other antibiotic showed low level of activity. Pulsed Field Gel Electrophoresis (PFGE) showed 14 different banding patterns that suggest isolates were of different clonal types.
Conclusion:
mecA was responsible for methicillin resistance in majority of strains. Polyclonal spread of MRSA infection in the study area indicates its diverse origin and possible lateral transfer. Thus, this study is of clinical interest in terms of selection of proper antimicrobial chemotherapy and infection control management.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) is prevalent in Northeast India, primarily driven by the mecA gene. The study highlights the need for effective antimicrobial chemotherapy and infection control due to polyclonal spread.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Methicillin resistance in Staphylococcus aureus (S. aureus) stems from modifications in penicillin-binding proteins, reducing beta-lactam antibiotic efficacy.
- This study investigates the prevalence of methicillin-resistant S. aureus (MRSA) in both community-acquired (CA-MRSA) and hospital-acquired (HA-MRSA) infections in Northeast India.
Purpose of the Study:
- To determine the occurrence and characteristics of MRSA in Northeast India.
- To identify the genetic basis of methicillin resistance and assess antibiotic susceptibility patterns.
- To evaluate the clonal diversity of MRSA isolates.
Main Methods:
- Collected 197 S. aureus isolates from clinical samples in Northeast India.
- Screened for methicillin resistance using the cefoxitin disc diffusion test.
- Utilized Polymerase Chain Reaction (PCR) to detect mecA and mecC genes and Pulsed Field Gel Electrophoresis (PFGE) for DNA fingerprinting.
Main Results:
- Of 127 confirmed S. aureus isolates, 71 (55.9%) were identified as MRSA.
- The mecA gene was detected in 43 MRSA isolates; mecC was not found.
- Linezolid (83.6%) and teicoplanin (72.44%) showed the highest activity against MRSA, while vancomycin susceptibility was 66.14%. PFGE revealed 14 distinct banding patterns, indicating polyclonal spread.
Conclusions:
- The mecA gene is the primary determinant of methicillin resistance in the studied MRSA strains.
- The polyclonal nature of MRSA suggests diverse origins and potential for lateral gene transfer.
- Findings are crucial for guiding antimicrobial chemotherapy selection and infection control strategies in the region.
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