Antimicrobial Resistance Characteristics and Phylogenetic Groups of Escherichia coli Isolated From Diarrheic Calves in Southeast of Iran

Background: Antimicrobial resistance is one of the main challenges in diarrheal diseases in human and animals. Regardless to the main reason of the disease, approximately all antimicrobial actions including treatment, control and prevention are mostly centralized against Escherichia coli (E. coli) strains. Objectives: This work purposed to antimicrobial resistance (AR) and determinate virulence genes and phylogenetic groups in E. coli isolates (n=170) obtained from calves with diarrhea. Materials and methods: Isolates were molecular characterized for 17 AR genes and 3 phylogenetic sequences. AR phenotyping were performed on all strains for 12 antimicrobial agents by using disc diffusion method. Results: All AR genes but qnrS were identified with different prevalence in E. coli isolates that the most common genes were aadA (20%), blaTEM (11.7%) and sulII (11.2 %) belonging to aminoglycoside, β-lactamase and sulphonamide families, respectively. Resistance to the penicillin and sulphamethoxazole drugs was found in 100% of isolates and followed by tetracycline (73.5%), streptomycin (60%), trimethoprim sulphamethoxazole (56.5%) and kanamycin (53.5%). The phylogenetic groups A and B1 considerably surrounded the majority of isolates with the frequency of 65.8% and 30.6%, respectively. Conclusions: In Iran, diarrheic calves have an important role as reservoir of resistant E. coli strains against the some drugs which are registered for treatment of calf diarrhea.