Epidemiologic investigation of pathogenic Escherichia coli in domestic dogs in Nanchong area

Pathogenic Escherichia coli is a zoonotic bacterial pathogen that causes significant losses to the farming industry and threatens public health safety. Dogs, as companion animals, are closely intertwined with human life and health. Therefore, heightened attention to pathogenic E. coli in canines is particularly crucial. This study investigated the infection and incidence of canine pathogenic E. coli disease in Nanchong of Sichuan province in China. 3229 diseased dogs from 2020 to 2021, according to different seasons, gender, age, breed, and immunization status, were analyzed. Meanwhile, pathogenic E. coli was isolated and identified from the fecal samples of the sick dogs, and the virulence factors and drug resistance of the strains were also analyzed. The study identified 129 cases of pathogenic E. coli infections in dogs from 2020 to 2021, accounting for 4% of the total (129/3229). compared to factors such as season, sex, and immune status, there is a significant difference in the infection rates between different age groups of dogs (P=0.029). Canine pathogenic E. coli can be infected throughout the year, The study found that the highest rate of pathogenic E. coli infections in dogs occurred during spring, with summer having the second-highest rate, followed by winter. The infection rate of males was higher than that of females, the infection rate of juvenile dogs was higher than that of adult dogs, and the infection rate of small dogs was higher than that of medium-sized and large dogs. In addition, all 27 pathogenic E. coli strains isolated from diverse geographical regions demonstrated antibiotic susceptibility, with the lowest sensitivity to tetracycline at 60%, followed by amoxicillin, streptomycin, and butyl carbamate, with a sensitivity of 80%. The results of whole gene sequencing showed that the main virulence factors were Fimbriae, LPS, Brk, and the canine pathogenic E. coli in the Nanchong area had developed resistance to some antibiotics. Although the infection rate of pathogenic E. coli in canines was relatively low in Nanchong, it remains essential to advance research on its pathogenic characteristics, antimicrobial resistance patterns, and control measures. Concurrently, clinical antimicrobial use must be standardized, immunity in juvenile dogs enhanced, and environmental hygiene management within breeding facilities strengthened.