The molecular screening of the virulence gene and blaCTX gene of resistant Salmonella typhi in Iraq

The types of salmonella are among the most dangerous types of human health and safety, which are associated with many diseases. It is widespread and difficult to control. Preventive measures must be properly implemented to prevent the spread of this bacterium. The appearance of resistance strains of salmonella against some antibiotics led to serious complications in patients and thus inhibiting immunity with infection. Many different virulence factors play affects in the pathogenesis of this bacteria. The present project aimed to isolate and identify clinical Salmonella typhi in terms of antibiotic resistance, virulence genes and protein expression profiles (n = 139). 44 were excluded on suspicion of co-growth with other bacteria and final results showed only 11 positive (Salmonella typhoid). First, Salmonella verification was performed by chemical and molecular tests. Then electrophoresis gel test was performed. Finally, polymerase chain reaction test was performed. DNA was extracted from Salmonella samples for the investigation. After electrophoresis on an agarose gel, all of the isolates indicated the presence of bands at the same intensity. Extracted DNA was analyzed by spectrophotometer to determine concentration and purity using nanodrop technology. The purity of the DNA recovered from the tested isolates was found to be between fifteen and twenty five ng/μL. The Salmonella bacteria isolates were diagnosed using biochemical tests, as well as genetically characterized by 16SrRNA gene using polymerase chain reaction as a final diagnostic test. After diagnosis, we obtained isolates confirmed to be Salmonella. Its sensitivity to the antibiotics Piperacillin, Tazobactam, Ceftazidime, and Cefepime Aztreonam was tested. The results of Imipenem, Meropenem, Clavulanic Acid and Ticarcillin tests with the help of Vitek were as indicated in the results chapter. The genetic detection of some genes responsible for the virulence of Salmonella bacteria was conducted using the polymerase chain reaction the genes blaTEM, blaCTX, aadA, intI1, qnrA, qnrB, dfr and blaSHV were screened. blaTEM gene was not expressed in all isolates. While the blaCTX gene was expressed by 63% within the expected size of gene 754; the qnrA and qnrB genes were also revealed the qnrA gene was not expressed in the samples under study there is a 36% gene expression of qnrB within the 466 genome. The DNA samples were electrophoresed to detect blaSHV and Intl1 genes within the molecular size (865, 484) respectively, we did not observe any gene expression for all isolates.