Multidrug antibiotic resistance index and antimicrobial resistance patterns of Escherichia coli in intensive pig farms in Kenya

Antibiotic resistance is a significant global public health threat, rendering treating human and animal infections difficult, longer and expensive. This study was conducted to determine the antibiotic resistance profiles of Escherichia coli isolated from pig farming environments in selected pig farms around Kenya. Wastewater, the associated sludge, and ground surface boot sock samples were collected from preselected intensive pig farms. A total of 80 samples were collected from 16 intensive pig farms. The samples were cultured, and 112 E. coli isolates were identified using standard microbiological procedures and confirmed by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectroscopy (MALDI-TOF MS). Antibiotic susceptibility testing was performed using the Kirby-Bauer disc diffusion method against ampicillin, amoxicillin-clavulanic acid, gentamicin, trimethoprim-sulfamethoxazole, chloramphenicol, enrofloxacin and cefotaxime. The highest resistance was recorded against ampicillin at 27.7% and the lowest for cefotaxime at 7.1%. Multidrug-resistance was observed for 25.9% of the isolates. There was no significant difference between resistances from the sampling locations. Fisher's exact test conducted to determine the difference between resistance rates of different sample types and the antibiotics tested showed that trimethoprim-sulphamethoxazole showed a statistically significant difference (p = 0.003). The isolates had varied multidrug antibiotic resistance (MAR) indices, but the average index was 0.33. The mean MAR index was highest in boot socks samples (0.3 ± 0.3). Kruskal-Wallis test did not find a statistically significant difference between sample type and MAR index. The results suggest that there is potentially high antibiotic exposure in the intensive pig farms that may increase the selection pressure leading to the development and dissemination of antibiotic-resistant E. coli among pig populations. These findings highlight the presence of multidrug-resistant E. coli in intensive pig farm environments, posing a potential risk to humans and the wider environment, which may further compound the public health threat.