Determination of methicillin resistance genes of Staphylococcus aureus strains isolated from clinical specimens

Methicillin resistant Staphylococcus aureus (MRSA) is an important pathogen which is responsible for community acquired and nosocomial infections. With the long-term use of antibiotics this bacteria developed different resistance mechanisms. Treatment is extremely difficult and expensive. Rapid and accurate detection of methicillin resistance in S. aureus has become a key element on infection control measures and limiting the spread of this organism. The purpose of this study, determination of methicillin resistance genes of S. aureus strains isolated from clinical specimens. This study analyzed 48 Staphylococcus aureus strains isolated from the samples of the patients in Gazi University Medical Hospital. Identification of the strains was based on standart microbiological procedures (colony morphology, Gram stain, hemolysis on blood agar, DNase, catalase, coagulase reactions and mannitol fermentation) and methicillin resistance was determined by Kirby-Bauer disk diffusion method according to the suggestions of Clinical and Laboratory Standards Institute (CLSI). Although 39 of S. aureus strains were sensitive to methicillin (MSSA), 9 of them (EB3, EB4, EB6, EB17, EB18, EB33, EB36, EB46, EB47) were resistant to methicillin (MRSA). Detection of methicillin resistance in staphylococci by phenotypical methods often leads to false results. So, the most appropriate method for detecting the methicillin resistance for Staphylococcus aureus isolates are detection of mecA gene by polymerase chain reaction. To this end, for 9 methicillin resistant Staphylococcus aureus strains determined by disk diffusion method and 3 methicillin sensitive S. aureus strains (EB5, EB9, EB12), DNA extraction was performed by the boiling method and mecA gene was investigated by polimeraze chain reaction (PCR) method. The EB12 sensitive strain by disk diffusion method methicillin resistance gene was found to contain. This study show that, disk diffusion technigue should be supported by moleculer methods for detection of methicillin resistance.