Antimicrobial Resistance Profile of Salmonella Enterica Isolated from Improved Poultry Breed Farming Chain, Maharashtra, India

Aims: With rising demand for poultry meat, globally backyard farms have adopted semi-intensive systems using improved birds. Food safety is a prime issue in antimicrobial-resistant Salmonella spp. found in meat, which has often been traced back to farms. Study Design: We carried out a cross-sectional prospective study. Place and Duration of Study: The study was conducted in selected districts of Maharashtra India during October 2023 to March 2024. Methodology: A total of 364 samples were collected from improved indigenous poultry breed hatcheries (n=5), improved indigenous breed commercial farms (n=5), and improved breed rearing backyard poultry setups (n=30) in Marathwada, Maharashtra state, India. The isolation of Salmonella spp. was carried out as per IS-5887 (Part 3): 1999 protocol. The bacterial isolates were further identified by cultural, microscopic morphology and biochemical characteristics (BAM 2007). Confirmation of Salmonella spp. was done by polymerase chain reaction (PCR) assays with primers designed for the invA gene. All Salmonella isolates were subjected for antibiotic susceptibility testing by disk diffusion method against 14 commonly used antimicrobials. Further, isolates were characterized for the presence of blaTEM, blaSHV, blaOXA, blaCTXM, tetA, and Sul1 AMR genes. Results: A total of 15 isolates recovered with prevalence rates of 4.83, 6.36, and 1.53 percent in hatcheries, farms, and backyard households, respectively. Five isolates that were randomly analyzed showed a homologous sequence as Salmonella enterica. Antimicrobial susceptibility testing of all isolates revealed higher resistance against Erythromycin (100%), followed by Ceftazidime (40%), while sensitivity (93.33%), was recorded against Ampicillin/Sulbactam, Amoxicillin/Sulbactam, and Enrofloxacin. The average multiple antibiotic resistance (MAR) index, of Salmonella isolates was 0.117. Genotypic resistance pattern revealed that all isolates (100%) were carrying the blaTEM gene, while none were harbouring broad spectrum extended-spectrum beta-lactamases (blaSHV, blaOXA, and blaCTXM) genes. All isolates were positive for the tetA gene (100%) but none of them was positive for Sul1 genes. Conclusion: The study highlights the low antimicrobial resistance in Salmonella isolates isolated from Improved Poultry Breed Farming Chain, which might be due to low usage of antimicrobials. However, monitoring of multidrug-resistant Salmonella enterica in improved poultry breed farming chains is essential to protect human health.