Prevalence of Antimicrobial-Resistant Bacterial Pathogens Among Livestock in Subtropical Environments

Background/Objectives: The prevalence of resistant pathogens in livestock and the environment threatens human health. Frequently used antibiotics in livestock gradually increase the resistance pattern, which intimately threatens the livestock industry. Methods: About 536 pathological samples were collected from January 2023 to December 2024 from chicken (472), birds (2), goat (25), sheep (12), and cows (21) and buffaloes (4), across the Sindh, Pakistan. A wide variety and number of bacterial pathogens were isolated and identified. After performing their antibiogram study, phylogenetic analysis was also performed. Results: The prevalence of different bacterial infections was studied in livestock. Salmonella spp. was found to be the most common cause of bacterial infection in livestock (77.79%), followed by Escherichia coli (62.69%) and Staphylococcus aureus (8.02%). The highest number of Salmonella spp. and S. aureus isolates were found to be resistant to ampicillin (80.67% and 81.4%, respectively), while E. coli isolates were found to be resistant to amoxicillin (97.87%) majorly. MARI revealed that 79.7% of Salmonella spp., including all MDR strains (n = 332); 55.59% of E. coli (n = 336), and 88.37% of S. aureus (n = 43) had indexes greater than 0.2. 16S bacterial identification and phylogenic analysis were performed through molecular methods. Conclusions: AMR is one of the most considerable livestock health issues that also affect human health. The MARI indicate a high rate of antibiotic use and resistance in the isolated Salmonella, E. coli, and S. aureus require the urgent need for continuous antimicrobial susceptibility surveillance and control of antibiotic use in livestock.