الفهرس 
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Abstract
The aim of this work is to investigate the presence of mecA gene and class 1 integron between multidrug resistant MRSA.
In this study a total of two hundred and twenty staphylococcal isolates were collected from 3 Egyptian hospitals (Abbassia fever hospital, Cairo hospital and Ain-shams hospital). Clinical samples were collected from urine, pus discharge and wound, (54%) isolates were recovered from urine, (40.4%) from wound and (13.6%) from pus discharge, (45.5%) were from males and (54.5%) were from females.
All of the isolates were identified as Staphylococcus aureus (SA) as they produce golden yellow colonies on mannitol salt agar medium, also black, shiny and convex colonies with clear zones on Baird-Parker agar media and they were positive for catalase, coagulase. In addition, isolates were confirmed as S. aureus by Microscan biotyper automated system.
Antibiotic susceptibility test showed that the isolates were multidrug resistance against the tested antibiotics with various extents. The percentage of antibiotic resistance can be summarized as; 81.8% of isolates were resistant to methicillin, 65% were resistant to trimethoprim-sulphamethaxole, 60% were resistance to amikacin, 46.3% were resistance to ciprofloxacin, 44.5% were resistance to erythromycin, 44% were resistance to clindamycin, 43.6% for doxacycline, 40% for vancomycin, 36.3% for imipenem and 11% of isolates were resistant to all tested antibiotic groups. Minimal inhibitory concentration showed relatively high MIC that 65% and 58% of isolates were resistant to amikacin and imipenem.
One hundred of isolates were examined for the presence of methicillin resistant (mecA) gene, integrase (intI1) gene, dehydropetroat synthase (sul1) gene and class1 integron by PCR amplification; forty two percent of the isolates were found to carry class1 integron gene cassettes with variable amplicon size ranges from 100 to 1000 bp as well as 36% of isolates carrying (intI1) integrase gene with the amplicon size of 430 bp and 11% of isolates harbor dehydropetroate synthase gene (sul1) with the amplicon size of 110 bp which confer resistance to sulfonamide, furthermore the methicillin resistant gene (mecA) was detected in 80% of MRSA isolates, unexpectedly twenty percent of the phenotypically MRSA isolates were found to be mecA gene negative.
The distribution of mecA gene and class1 integron genes cassettes among nosocomial sources were found to be predominant in urine than in pus discharge and wounds as follow; 32%, 25% from urine, 15%, 5% from pus discharge and 28%, 12% from wounds for mecA and CS1 genes cassettes.
In the current study, 16% of isolates were found to have a typical integron structure, the integrase (intI) gene with its promoter (PintI), an integration site named attI (attachment site of the integron) and a constitutive promoter (Pc) for the gene cassette integrated at the attC site and a cluster of gene cassettes, 26% of isolates carry (CALIN) element a cluster of attC site lacking integron-integrase and 20% were In0 having integrase gene only without any gene cassettes and finally 38% of isolates have no integron element detected in them.
Among 100 isolates of MRSA, 42 isolates were identified as being positive for class1 integron. Representative PCR products of 8 isolates with class1 positive strains were sequenced. PCR product of sul1 gene in the isolate ATCC 29213 was sequenced. The class1 gene cassettes were variable ranged between 110 – 906 bp. The sequence of these cassettes showed various genes content. The Qac resistance gene emrE as betB was detected in 4 cassettes; the hypothetical protein (TetR/AcrR family transcriptional regulator and YdeI/OmpD polymyxin resistant protein) was detected in 2 cassettes. The putative integron gene cassette protein (ABC transporter permease) was also detected in one cassette. The dehydropetroate synthase gene Sul1 was detected.
The high prevalence of integron in multi-drug resistant isolates highlights the urgent need to employ effective means to avoid dissemination of drug-resistant bacteria.