IJCRR. 2015; 7(10): 55-60
A COMPARATIVE STUDY OF OXACILLIN SCREEN AGAR, OXACILLIN DISC DIFFUSION AND CEFOXITIN DISC DIFFUSION, OXACILLIN E-TEST METHOD FOR ROUTINE SCREENING OF METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS
Anamika Vyas, Megha Sharma, Sanjeev Kumar, Mrityunjay Kumar, Sudhir Kumar Mehra.
Background: Methicillin resistant staphylococcus aureus (MRSA) has been recognized as one of the major pathogen in both hospital and community settings. MRSA strains are frequently resistant to different class of antibiotics. Multi drug antimicrobial resistance among MRSA is a matter of concern for clinicians. Therefore, an accurate detection of MRSA in microbiology labora- tory is essential for patient management and epidemiological purpose including hospital infection control. Aim: The present study was undertaken to compare various phenotypic methods (oxacillin disc diffusion, cefoxitin disc diffusion, oxacillin screen agar) for detection of MRSA using E test MIC oxacillin as gold standard method. We also aimed to study the resistance pattern of the MRSA isolates. Materials & Methods: A total of 50 staphylococcus aureus strain which were isolated from different clinical specimens were included in this study. All isolates were tested for methicillin resistance by oxacillin disc diffusion, cefoxitin disc diffusion and oxa- cillin screen agar test considering E test MIC for oxacillin as gold standard. All the isolates were tested for antibiotic susceptibility testing by kirby bauer disc diffusion method against a predefined panel of antimicrobials and intepretation was done according to CLSI guidelines. Result: Among the 50 staphylococcus auresus isolates 23 (46%) isolate were identified as MRSA by E test MIC method. Ce- foxitin disc diffusion test showed 100% sensitivity and 92% specificity while oxacillin disc diffusion test and oxacillin screen agar test showed 100% sensitivity and 74% specificity. The resistance percentage of MRSA isolate to erythromycin, ciprofloxacin, levofloxacin, cotrimoxazole and gentamycin was 70%, 96%, 57%, 52% and 43% respectively. All isolates were sensitive to vancomycin, linezolid and tigecycline. Conclusion: Our study revealed that cefoxitin disc diffusion test had high sensitivity and high specificity as compared to other phenotypic methods used routinely to detect MRSA. This method is technically less demanding even can be used along with antibiotic sensitivity testing, cost effective and can be the best option to detect MRSA in clinical settings with constraint facilities. Vancomycin is still the drug of choice for treatment of MRSA, However regular monitoring of vancomycin sensitivity should be done as reduced susceptibility to vancomycin has been reported from all over the globe and is a matter of concern for clinicians.
MRSA, Cefoxitin disc diffusion, Oxacillin disc diffusion