Comparative evaluation of conventional method versus polymerase chain reaction for detection of methicillin resistant staphylococcus aureus isolated from blood stream infections

Shreyashi Tuladhar; Narayan Raj Bhattarai; Ratna Baral; Keshav Rai; Basudha Khanal

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ORIGINAL ARTICLE

Year : 2020 \| Volume : 6 \| Issue : 1 \| Page : 38-42

Comparative evaluation of conventional method versus polymerase chain reaction for detection of methicillin resistant staphylococcus aureus isolated from blood stream infections Shreyashi Tuladhar¹, Narayan Raj Bhattarai², Ratna Baral², Keshav Rai³, Basudha Khanal⁴ ¹ Lecturer, Dept. of Microbiology, Patan Academy of Health Sciences, Lagankhel, Kathmandu, Nepal, India ² Additional Professor, Dept. of Microbiology and Infectious Diseases, B.P. Koirala Institute of Health Sciences, Ghopa, Dharan, Nepal, India ³ Senior Demonstrator, Dept. of Microbiology and Infectious Diseases, B.P. Koirala Institute of Health Sciences, Ghopa, Dharan, Nepal, India ⁴ Professor and Head, Dept. of Microbiology and Infectious Diseases, B.P. Koirala Institute of Health Sciences, Ghopa, Dharan, Nepal, India Correspondence Address: Shreyashi Tuladhar Lecturer, Dept. of Microbiology, Patan Academy of Health Sciences, Lagankhel, Kathmandu, Nepal India Source of Support: None, Conflict of Interest: None

Background: Clinically significant bloodstream infection (BSI)due to Staphylococcus aureus(S.aureus)isa significant pathogen in community acquired and nosocomial BSI. Methicillin Resistant Staphylococcus aureus (MRSA) are resistant to methicillin and all χ-lactam antibiotics due to possession of mec A gene. Several phenotypic methods for laboratory detection of MRSA: oxacillin screening test, oxacillin or cefoxitin disc diffusion method, oxacillin minimum inhibitory concentration test are used routinely in our setting. Aim: We aim to detect MRSA among blood culture isolates by conventional method (cefoxitin disc) and also to confirm identity of these MRSA strains by molecular method i.e. mecA detection by Polymerase Chain Reaction(PCR). Materials and Methods: This cross sectional study was carried out on 139 S. aureus clinical isolates in Department of Microbiology from blood samples submitted for culture and sensitivity test. Once the isolate was identified as S. aureus, it was further identified as MRSA or Methicillin Sensitive Staphylococcus aureus (MSSA) by use of antimicrobial discs. DNA extraction was done by boiling method. Results: Antimicrobial susceptibility pattern documented resistance of 48.9% of isolates to cefoxitin (MRSA). 80.2% and 63.3% of isolates were resistant to penicillin and cotrimoxazole respectively. All isolates were susceptible to vancomycin. Conventional PCR was carried out for all 139 samples. 51.1% of isolates harbored mecA gene thus identified as MRSA. Conclusion: As expected PCR performed superior, however due to less cost, simplicity and easy availability, cefoxitin disc diffusion test holds a significance as an alternative to PCR for detection of MRSA on routine basis in a resource limited setting like ours.



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