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Evaluation of three methods for detection of methicillin resistant staphylococcus aureus (mrsa)

Authors:Stephen T Odonkor and Kennedy K Addo
Int J Biol Med Res. 2011; 2(4): 1031 – 1034  |  PDF File

Abstract

Methicillin resistant Staphylococcus aureus (MRSA) strains have become a well-known etiologic agent of a wide variety of infections worldwide. Considering the increasing rate of infections caused by MRSA, performance of reliable, accurate and rapid testing for detection of MRSA is essential for both antibiotic therapy and infection control measures. The aim of this study was to evaluate 3 methods for detection of MRSA and to determine its β lactames production profile. Two hundred and fifty (250) S. aureus isolates from routine microbiological specimen were collected from hospitals in Accra, Ghana between July and December 2011 for the study. The isolates were obtained from cultures of different specimens including wounds, sputum, blood, aspirates, urine, and cerebrospinal fluids. Methicillin disc diffusion (5µg), Oxacillin disc diffusion (5µg), β lactamase test (using nitrocefin disc) and MRSA screening assay test were performed on the isolates. Out of the 250 isolates the methicillin disc diffusion test detected 54 representing 21.6% as MRSA positive and 196 representing 78.4% as negative. Oxacillin disc diffusion test detected 78 (31.26%) to be MRSA and 172(68.8%) as negative. The MRSA screen assay detected 84(33.6%) as MRSA and 166(66.4%) as negative. One hundred and fifty eight of the isolates produced β-lactamase. All phenotypic methods had significant differences in sensitivity and specificity for detection of MRSA. However, MRSA screen assay method in comparison to other methods had higher specificity and sensitivity for detection of MRSA in resource constraint settings.