Examination of Pathotypes, Phylogroups, and Antibiotic Resistance of Escherichia coli Isolates Obtained from Diarrheic Pet Dogs

Intestinal pathogenic Escherichia coli (DEC) remains a significant zoonotic etiological agent causing diarrhea leading to fatalities in both humans and animals. This study aimed to assess the pathotypes, phylogroups, and antimicrobial resistance profiles of DEC isolates obtained from pet dogs and analyze their interrelationships. Two hundred E. coli isolates were collected from rectal swab samples of 40 diarrheic and 40 apparently clinically healthy (non-diarrheic) pet dogs puppies aged between 1-6 months, between January and June 2023. After E. coli isolation using classical conventional methods, their identification was performed phenotypically using the BD Phoenix 100 automatic microbiology system and confirmed genotypically using PCR. Pathotypes (EHEC, EPEC, ETEC, EIEC) and phylogenetic groups (A, B1, B2, C, D, E, F, Clade 1) of isolates were investigated via multiplex PCR. Resistance profiles to 19 antibiotics belonging to ten antimicrobial families were determined using the BD Phoenix 100 automated microbiology system with NMIC/ID 400 Gram negative identification cards. The relationship between the clinical status of the sampled dogs (diarrheic and healthy) and the antibiotic resistance profiles, multi-drug resistance (MDR), pathotypes, and phylogroups of E. coli isolates was analyzed using the Chi-square (chi 2) 2 ) test. Pathotyping revealed that all E. coli isolates belonged to EHEC (47.2%), EPEC (34.5%), ETEC (12.8%), and EIEC (5.5%) pathotypes, while phylogenetic analysis indicated that the isolates were distributed among filogroups B2 and C (23.7%), D (20.0%), B1 (12.7%), E (9.0%), F (3.6%), and A (1.8%). Antibiotic susceptibility test results revealed that 78.2% of isolates exhibited MDR. Significant statistical associations were observed between the clinical status of dogs and resistance to ampicillin, amoxicillin-clavulanic acid, ciprofloxacin and tigecycline. However, no significant statistical relationship was found between multi-drug resistance profiles, pathotypes and phylogroups of the isolates. The presence of virulence genes specific to DEC pathotypes in canine isolates indicated that apparently healthy pet dogs could serve as a potential source of human infections, similar to diarrheic dogs. The presence of diverse phylogroups highlights the population diversity of E. coli, , while the high prevalence of multi-drug resistant isolates underscores the necessity for careful antibiotic selection in the treatment and control of infections.