Comparative occurrence and antibiogram of extended-spectrum β-lactamase-producing Escherichia coli among post-weaned calves and lactating cows from smallholder dairy farms in a parallel animal husbandry area

BACKGROUND AND AIM: Inappropriate overuse of antimicrobials might be associated with the spreading of antimicrobial-resistant bacteria in animal-based food products. Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli have been recognized as an emerging global problem in a One Health approach. This study aimed to assess the occurrence and antimicrobial-susceptible profiles of ESBL-producing E. coli among post-weaned calves and lactating cows in a parallel animal husbandry area. MATERIALS AND METHODS: Seventy-two pool fecal samples were collected from 36 smallholder dairy farms registered in Ban Hong Dairy Cooperatives, Lamphun Province, Thailand. Pre-enriched fecal samples were cultured in MacConkey agar supplemented with cefotaxime. The potential E. coli isolates were identified by not only biochemical tests but also polymerase chain reaction assay of the 16S rRNA gene. ESBL production was confirmed by the combination disk test. Antimicrobial susceptibility testing was performed by the Kirby–Bauer disk diffusion method. RESULTS: The occurrence of ESBL-producing E. coli at the farm level was 80.56%. The different phenotypic antibiogram of ESBL-producing E. coli was observed among post-weaned calf and lactating cow specimens. The most frequent resistance patterns of ESBL-producing isolates from both groups were amoxicillin-ceftiofur-cephalexin-cephalothin-cloxacillin-streptomycin-oxytetracycline-sulfamethoxazole/trimethoprim. For the median zone diameter, enrofloxacin-resistant isolates with narrow zone diameter values from lactating cow specimens were particularly more than post-weaned calf specimens (p<0.05). CONCLUSION: These findings revealed the dynamic changes in ESBL-producing E. coli from calves and lactating cows in Lamphun Province, posing the inevitability to prevent bacterial transmission and optimize antimicrobial therapy in dairy farming.