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MECHANISM, DETECTION AND PREVALENCE OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS IN SAUDI ARABIA

Vinod Kaul & Md. Zeyaullah

Methicillin-resistant strains of Staphylococci were identified immediately upon the introduction of methicillin into clinical practice. Resistance was termed “intrinsic” because it was not due to destruction of the antibiotic by β- lactamase. Further studies revealed that methicillin resistance requires the presence of the mec gene. The mec gene is absent from susceptible strains and present in all resistant strains. Mec gene, encodes the penicillin binding protein 2a (PBP2A) that establishes resistance to methicillin and other semisynthetic penicillinase-resistant beta-lactams. Penicillin-binding proteins are peptidase enzymes located in the bacterial membrane that catalyze the transpeptidation reactions of peptidoglycan during cell wall synthesis. The most accurate methods to detect methicillin-resistant S. aureus (MRSA) are polymerase chain reaction (PCR), for detection of the mecA gene and latex agglutination tests for the protein product of mecA, penicillin binding protein 2a. Cultures are also important tool for surveillance from body sites (mostly the anterior nares) that are frequently colonized with MRSA. The majority of patients with asymptomatic MRSA colonization will be detected by screening culture from the anterior nares. Traditional methods used to process surveillance cultures take 48 to 72 hours to yield results. However, newly available techniques shorten the amount of time required to detect MRSA in surveillance cultures. A chromogenic selective agar containing cefoxitin detects a majority of MRSA isolates within 24 hours. Reports of MRSA infections are increasing worldwide, In Saudi Arabia, many institutions have reported an increase in the incidence of MRSA in recent years; other institutions have reported a variation in incidence. In one study from Saudi Arabia, MRSA, has been detected as high as 55.3%, whereas earlier studies conducted in the Jeddah hospitals showed a lower prevalence, with only minor variation between 6.5% and 8.9%.