oa Molecular Diagnosis and Vaccines - Characterization of methicillin - resistant Staphylococcus aureus isolates from patients at a major hospital in Doha, Qatar
Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important causes of hospital infections worldwide. The mecA gene causes high-level resistance to methicillin. Detection of the MRSAspecific gene using mecA polymerase chain reaction (PCR) has become an important tool for rapid detection of MRSA. Molecular typing of MRSA is crucial for controling the spread and knowing the source of infection. In this study, twenty S. aureus isolates were subjected to mecA PCR then genotyped by pulsed field gel electrophoresis (PFGE) using BamHI restriction enzyme. A 100% correlation was found between the PCR and standard agar plate methods for the detection of MRSA and the 533bp product of mecA amplification was detected in all isolates despite the difference in the type of specimens. PFGE yielded 14 different patterns. 12 isolates made six clusters, each cluster consisted of one pair of isolates while the remaining 8 isolates were non-clustered. Out of the six clusters, three showed more than 80% similarity, while the remaining three pairs showed less than 60% similarity of their restriction fragments. It is concluded that the mecAPCR is a rapid and inexpensive method for diagnosis of MRSA and that PFGE provides a useful tool, being able to determine the relatedness between MRSA. The presence of un-related multi -resistant MRSA strains in the hospital supports the hypothesis that horizontal transfer plays an important role in the dissemination of the mecA gene in the S. aureus population.
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