Staphylococcal Cassette Chromosome imec/i(SCCimec/i) Gene Typing in Detection of Methicillin-Resistant iStaphylococcus aureus/i: Toward Precise Detection in Health Care Facility

摘要

Background: Blood stream infections (BSI) are considered key issues in critical care units. Methicillin resistant Staphylococcus aureus, MRSA-related infections, are considered a major health problem. This is attributed to the emerging new society dangerous strains with continuous antibiotics pressure and fluctuations in resistance patterns. Aim: We aimed to study epidemiology of methicillin resistance S. aureus (MRSA) infections by using conventional phenotypic methods [cefoxitin disk diffusion (CDD) and oxacillin screening agar] and molecular typing of the mec-gene (SCCmec) using multiplex PCR in Suez Canal University Hospital. Methods: 100 non-repetitive staphylococcus aureus were collected and identified morphologically and biochemically by standard laboratory procedures. The strains were considered MRSA if the MIC of oxacillin ≥ 4 μg/ml, and the inhibition zone of cefoxitin was ≤21 mm (CDD). Characterization of SCCmec elements in isolated MRSA strains was done via multiplex-PCR. Results: From total of 100 isolates, eighty were detected as MRSA by using CDD (sensitivity and specificity were 83.6% and 24.4% respectively) and only 65 by using oxacillin screening agar (sensitivity and specificity were 85.5% and 60% respectively). MecA gene was identified in 55 samples;the majority of isolates were SCCmec type IVa (63.7%). Both type I and III of SCCmec couldn’t be detected. Antimicrobial sensitivity rates among SCCmec-V isolates were expectedly higher than those among Type-II isolates. SCCmec type II was characterized by 100% resistant to ciprofloxacin, erythromycin, oxacillin and cefepime as well as greater resistance to clindamycin (70%) with the same pattern between all typing strains (7 strains). Conclusion: SCCmec types IVa and V are generally dominant in our community with no detection of SCCmec types I or III. PCR is the optimum method for MRSA detection.