Prevalence and antibiotic resistance profiles of Salmonella serotypes isolated from backyard poultry flocks in West Bengal, India

The present study was conducted to determine prevalence, virulence gene profile, serotyping, and antibiotic resistance patterns of Salmonella in birds kept under the backyard system in West Bengal, India. The study also incorporated the detection of Salmonella prevalence in their environment, including feed, drinking water, utensils, litter, dried manure under the house, soil, and eggs, which helped to formulate a biosecurity strategy. The study was conducted in 4 agro-climatic zones, such as the terai, new alluvial, red laterite, and coastal. Out of 360 samples, 22 Salmonella isolates (6.1%) were identified. Salmonella were isolated from cloacal swabs of 6 birds (15%, n = 40), from 4 feed samples (10%, n = 40), 8 drinking water samples (20%, n = 40), and 4 eggs (10%, n = 40). Similar antigenic structure, nucleotide sequence (invA) of Salmonella Enteritidis and Typhimurium, and randomly amplified polymorphic DNA banding patterns of Salmonella Enteritidis were observed. It seems that the same Salmonella isolate was present in feed sample, cloacal swabs, and eggs in the terai zone, whereas, it was found in drinking water, birds, and eggs in the new alluvial and in drinking water and birds in the coastal zone. A zone-specific biosecurity strategy was formulated based on the findings. The isolates were found to be resistant to chloramphenicol, ciprofloxacin, gentamicin, levofloxacin, norfloxacin, and oxytetracycline. None of the isolates possessed genes for major extended spectrum beta-lactamases. Thus, the present study identified the source of Salmonella contamination in the backyard chickens and their eggs in India with possible forms of biosecurity strategies. Our study was the first attempt in India to determine the prevalence, virulence gene profile, serotyping, and antibiotic resistance pattern of Salmonella in backyard birds, including the environment and product.