Background and Aim: Antibiotic-resistant infections are one of the leading threats to public health globally. Indiscriminate use of antibiotics in food animal production is an important driver of resistance, particularly among foodborne pathogens such as non-typhoidal Salmonella enterica (NTS). While there has been extensive research on antimicrobial-resistant (AMR) S. enterica in India and China, there have been few studies in countries in South Asia, including Nepal. This is particularly important with the rise of commercial poultry farming in Nepal as a means of economic development and nutritional subsistence. This descriptive study seeks to identify the prevalence and resistance patterns of NTS serotypes focusing on Chitwan, Nepal's leading poultry producing district.

Materials and Methods: A mixture of purposive and judgment sampling of 18 poultry farms and 20 slaughterhouses representing a broad geographic distribution across multiple municipalities in Chitwan was conducted in May 2019. Environmental samples taken from poultry farms included: Water, litter, feces, feed, farm swabs, and eggshell swabs. Biological samples taken from nearby slaughterhouses included: Muscle, heart, liver, skin, cecum, crop, and spleen. Samples were cultured and tested for the presence of NTS. Positive isolates were serotyped and tested for antimicrobial susceptibility to seven antibiotics known to be important to both human and animal health regionally. Farm practices were also characterized through a survey, the results of which are detailed in the accompanying paper.

Results: Out of 708 samples (288 environmental and 420 biological), 103 (15%) tested positive for NTS (9% of environmental; n=26, 18% of biological; n=77). The percentage of positive environmental and biological samples varied by source. Environmental sample positive rates were water (27.5%), feces (10.6%), litter (8.6%), farm swabs (5%), feed (1.8%), and eggshells (0%). Biological sample positive rates were skin (28%), heart (23%), crop (20%), muscle (15%), liver (15%), spleen (15%), and cecum (12%). Out of 103 positive S. enterica isolates, 48.5% were identified as Salmonella Typhimurium, 35% Salmonella Enteritidis, 7.8% Salmonella Gallinarum, 4.9% Salmonella Virchow, and 3.9% were Salmonella Agona. Of the 103 positive isolates, 80 (78%) were resistant to at least one antibiotic, and 21 (20%) were multidrug-resistant (MDR).

Conclusion: NTS is highly prevalent among Chitwan's growing poultry industry with higher rates of positivity found in slaughterhouse samples compared with environmental samples from farms. In addition, a high rate of AMR (78%) was revealed, and an extremely concerning number of those were shown to be MDR (20%). This baseline data has important implications for poultry production and consumption in the region. Further research will elucidate the extent to which this contamination and drug resistance is impacting the health of the local population and help inform treatment and management strategies.

Note: The characterization of the poultry industry and practices that might be linked to NTS contamination in the Chitwan district are detailed in the previous paper in this series (www.veterinaryworld.org/Vol.14/February-2021/14.pdf).

Keywords: antibiotic resistance, Nepal, non-typhoidal Salmonella, poultry, serotype.