University of Khartoum

Genotypic and Phenotypic Methods for Detection of Methicillin Resistant Staphylococcus aureus

Genotypic and Phenotypic Methods for Detection of Methicillin Resistant Staphylococcus aureus

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Title: Genotypic and Phenotypic Methods for Detection of Methicillin Resistant Staphylococcus aureus
Author: Elradi, Amel Hassan Ahmed Zaroug
Abstract: Back ground: Methicillin-resistant Staphylococcus aureus (MRSA) is a global public health problem. MRSA strains are frequently resistant to different class of antibiotics. Multi drug resistance among MRSA is a matter of concern for professional health workers worldwide. Therefore, an accurate detection of MRSA in microbiology laboratory is essential and of high value for patient management and epidemiological purpose including hospital infection control. The present study was undertaken to compare various phenotypic methods including antimicrobial resistance tests (oxacillin disc diffusion, Cefoxitin disc diffusion and E-test Minimum Inhibition Concentration (MIC) oxacillin for detection of MRSA), comparing to the Genotypic methods by using Polymerase Chain Reaction (PCR) technique as gold standard method. Materials and Methods: One hundred strains of S. aureus clinical isolates were used in the study. PCR for the presence or absence of the mecA gene and routine antibiotic susceptibility testing were performed including oxacillin (1µg), Cefoxitin (30µg), Amoxicillin (25µg), Erythromycin (15µg), Cefotaxime (30µg), E-test MIC oxacillin. All the isolates were tested for antibiotic susceptibility testing using kirby bauer disc diffusion method against a predefined panel of antimicrobials, and interpretation was done according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Results: Out of the 100 Staphylococcus aureus clinical isolates, 40 mecA gene positive and 60 mecA gene negative by PCR. Cefoxitin (30µg) disc diffusion test showed 97.5% sensitivity and 100% specificity while Oxacillin (1µg) disc diffusion test showed 92.5% sensitivity and 100% specificity. The resistance percentage of MRSA isolate to Amoxicillin (25µg), Erythromycin (15µg), and Cefotaxime (30µg) was 92.5%, 82.5%, 90% respectively. E-test MIC oxacillin showed 92.5% sensitivity and 100% specificity. Conclusion: Results of Cefoxitin disc diffusion test is in concordance with the PCR for mecA gene. Thus, the test can be an alternative to PCR for detection of MRSA in resource constraint settings.
Description: 69 Pages
URI: http://khartoumspace.uofk.edu/123456789/27120
Date: 2017


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