Molecular identification and characterization of Salmonella species isolated from poultry value chains of Gazipur and Tangail districts of Bangladesh

The aim of this study was to identify and characterize Salmonella species isolated from poultry value chains of Gazipur and Tangail districts of Bangladesh during the period of October 2015 to May 2016. For this purpose a total of 153 samples (35 chick meconium, 49 cloacal swab, 30 poultry carcass, 14 feed, 16 water, 7 transport swab, 2 floor swab) were collected and were subjected to various cultural, biochemical techniques and polymerase chain reaction (PCR). Furthermore, the isolated Salmonella species were characterized by antimicrobial susceptibility testing. Among the samples, 23.53% (n=36) were found to be associated with Salmonella species. The Salmonella species were identified by observing black centered colonies on XLD agar, positive to MR test and negative to VP and Indole test. All isolates of Salmonella species were positive to 16s rRNA gene based PCR (574 bp). Serogrouping of Salmonella species were performed by slide agglutination test using commercial Salmonella specific polyvalent O (A-I) antisera, Salmonella O group B (Factor O: 4, 5, 27) antisera and Salmonella O group D (Factor O: 9, 46) antisera. Among the 36 isolates, 30.56% (n=11) belonged to serogroup B and rest of the isolates 69.44% (n=25) to serogroup D. The most prevalent serogroup identified in this study was serogroup D. The isolated Salmonella species were subjected to antimicrobial susceptibility testing with the aid of disk diffusion method using 8 antimicrobial agents. All isolates of Salmonella species were susceptible to ciprofloxacin, norfloxacin, streptomycin and gentamicin. Out of 36 isolates 100% Salmonella species were resistant to erythromycin and tetracycline. The findings of this study revealed the presence of multidrug resistant Salmonella species in poultry value chains of Gazipur and Tangail districts of Bangladesh that posseses a serious threat to public and poultry health. To the best of our knowledge, this is the first report on the prevalence, serogrouping and antimicrobial resistance patterns of Salmonella species from poultry value chains of selected districts in Bangladesh.