Molecular characterisation and antimicrobial resistance of salmonella species isolated from chickens in elazig and surrounding area

The aim of this project was to obtain quantitative data about the frequency, molecular characterization and antibiotic resistance status of Salmonella agents in chicken flocks located in Elazığ and the surrounding area. For this reason, feces samples representing at least 20% of the flock area were collected via sock swabs from poultry flocks in the study region in addition to internal organs (liver, spleen, intestine) collected at necropsy of suspected chickens belonging to small family enterprises. The samples were analysed by conventional bacteriological methods ISO 6579:2002 /Amd 1:2007 and the suspected colonies were identifed at the genus level by PCR using primers specific to invA gene. Subsequently, subspecies characterisation of the field isolates confirmed as Salmonella spp. was performed by multiplex PCR (mPCR). In addition, resistance status of the isolates to ampicillin, tetracycline, trimethoprim-sulfamethoxazole and chloramphenicol antibiotics were determined genotipically. In the analysis of sock swabs and internal organ samples collected from the total of 77 chicken flocks by the isolation steps of ISO 6579: 2002 /Amd 1:2007 protocol, Salmonella suspected colonies were detected in 84.4% (65/77) of the samples. As a result of PCR analysis combined with invA specific primers, 98.5% (n = 64) of the isolates were confirmed as Salmonella spp. In the mPCR analysis of the confirmed Salmonella isolates, the most prevalent serotype identified was S. Infantis with the proportion of 26.6% (17/64), followed by S. Enteritidis with 21.9% (14/64) and S. Typhimurium with 9.4% (6/64). The remaining 27 isolates of Salmonella could not be typed with the species-specific primers used in the study. A total of 64 isolates obtained in this study were examined by mPCR using primers specific to resistance genes of ampicillin (blaTEM), tetracycline (tetA), trimethoprim-sulfamethoxazole (sul1) and chloramphenicol (cat1) antibiotics. According to the mPCR results, all the isolates of S. Infantis were resistant to tetracycline and trimethoprim/sulfamethoxazole, whereas only 11.8% (2/17) were resistant to ampicillin. It was also found that 66.7% (4/6) of S. Typhimurium isolates were resistant to ampicillin, while 33.3% (2/6) were resistant to trimethoprim-sulfamethoxazole and ampicillin. On the other hand, only one isolate of S. Enteritidis (7.14%) was determined to be resistant to trimethoprim-sulfamethoxazole, ampicillin and tetracycline. It was also determined that 63% (17/27) of Salmonella isolates which could not be characterized by species-specific primers used in this study were resistant to trimethoprim-sulfamethoxazole, while 14.8% (4/27) were resistant to tetracycline and ampicillin. Resistance to chloramphenicol was not detected in any of the isolates obtained in the study. In conclusion, Salmonella agents were detected in the majority (over 70%) of the farms in the region, and S. Infantis, S .Enteritidis and S. Typhimurium were found to be the most common serotypes respectively, in molecular characterisation by mPCR. These findings, when considered together with the results of other studies conducted in Turkey, indicate that Salmonella infections constitute a potential risk for chicken flocks. In addition, detection of significant resistance of the field isolates to ampicillin, tetracycline and trimethoprim-sulfamethoxazole antibiotics should be considered as an important output in terms of both human and animal health. Antibiotic susceptibility testing before the selection of antibiotics for the treatment of Salmonella infections is therefore important in preventing the use of random antibiotics and minimizing the development of resistance in strains.