PCR based early detection and antibiotic resistance pattern of Salmonella Gallinarum isolates from Pakistan poultry

The poultry industry in developing countries is still combating mortality and economic loss due to Salmonella contamination. Salmonella Gallinarum is a common pathogen of poultry birds, being the etiologic agent of fowl typhoid, which specifically infects adult birds via the oral-fecal route. Timely detection of S. Gallinarum in poultry flocks can allow early treatment intervention leading to a decrease in economic losses. Detection of S. Gallinarum is challenging, while its PCR-based detection is a promising strategy, however, due to its high genomic similarity with other commonly existing Salmonella spp., identification of S. Gallinarum from poultry samples with high specificity is still a challenge. The current study was conducted to isolate S. Gallinarum from different districts of Pakistan, assess their antibiotic susceptibility profile, and develop a method for its early detection. A total of 20 strains were isolated using buffer peptone water, selenite cysteine broth, and Xylose Lysine Tergitol-4 (XLT-4) agar supplemented with tergitol and characterized by biochemical procedures. The antibiotic sensitivity profile highlighted the highest resistance of isolates towards novobiocin and nalidixic acid, commonly used antibiotics in Pakistan Poultry production. The primers designed to amplify a unique genomic region of S. Gallinarum, showed successful detection of twenty S. Gallinarum strains, while no amplification with genomic DNA from other common Salmonella spp. The reported method can be utilized to detect S. Gallinarum from tissue samples of infected birds in a short time leading to early diagnosis and timely treatment intervention.