Isolation and Identification of Methicillin-Resistant Staphylococcus aureus from Keys of College Students Using Different Detection Methods

Aims: In this study, the methicillin-resistant Staphylococcus aureus (MRSA) were isolated and identified by using biochemical tests, antibiogram and polymerase chain reaction (PCR) to explore the circulation of MRSA among college students.
Study design: Cross-sectional study.
Place and Duration of Study: Department of Medical Microbiology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia between June 2010 and December 2010.
Methodology: A total of 100 samples were collected from keys of college students. There were 39 isolates (39 %) Gram-positive cocci and Catalase positive. 29 (74.36%) were glucose oxidation and fermentation positive. From the 39 isolates, 16 (43.24%) were shown Mannitol Salt Agar (MSA) tests positive. The deoxyribonuclease (DNase) tests and tube coagulase tests with human and rabbit plasma were carried out to improve the efficiency of the MSA test.
Results: 7 (43.75%) DNase positive and 2 (12.5%) tube coagulase positive. Both human and rabbit plasma showed similar sensitivity for the tube coagulase tests in this study. However, both isolates with tube coagulase positive were confirmed as S. aureus but not resistant to oxacillin, methicillin, erythromycin and cefoxitin. 2 (66.67%) of 3 (18.75%) isolates which is tube coagulase negative were resistant to erythromycin and 1 (33.33%) of them was resistant to methicillin. Rare strains of S. aureus can be coagulase negative. PCR assay was used. 1 (33.33%) of the coagulase negative isolate resistant to erythromycin was found to have nuc gene, mecA gene, ermC gene, msrA gene, linA gene, and femA gene. The isolate was confirmed as MRSA.
Conclusion: In conclusion, PCR technique is more sensitive and reliable than tube coagulase test or antibiogram for the detection of MRSA. And keys were shown to be an important source of MRSA and other bacteria circulation in the community.