ФЕНОТИПИЧЕСКАЯ И ГЕНОТИПИЧЕСКАЯ ХАРАКТЕРИСТИКА АНТИБИОТИКОРЕЗИСТЕНТНОСТИ ESCHERICHIA COLI И CAMPYLOBACTER JEJUNI, ВЫДЕЛЕННЫХ ИЗ ФЕКАЛИЙ ТЕЛЯТ

Antimicrobial resistance among bacterial pathogens associated with neonatal calf diarrhea is a significant challenge for veterinary medicine. This study aimed to characterize the phenotypic and molecular genetic profiles of antimicrobial resistance in Escherichia coli and Campylobacter jejuni isolated from calves within the first month of life showing clinical signs of diarrhea. A total of 25 fecal samples from Simmental calves were examined. Isolates were identified by MALDI-TOF MS, antimicrobial susceptibility was determined by disk diffusion, and resistance genes and mobile genetic elements were detected by real-time PCR. Thirteen E. coli isolates (52.0%) and four C. jejuni isolates (16.0%) were recovered. Among E. coli, the highest resistance rates were observed for ampicillin and ceftriaxone (92.3% each) and co-trimoxazole (76.9%); an MDR phenotype was detected in 84.6% of isolates. Molecular analysis of six representative E. coli isolates revealed a broad range of resistance determinants and mobile genetic elements, including blaTEM, blaCTX-M, blaCMY, mcr-1, intI1, and IS26. Among C. jejuni, resistance to tetracycline and ciprofloxacin was detected in 50.0% of isolates, while susceptibility to macrolides was retained. The tetA, tetO, and IS26 markers were detected in all isolates. These findings demonstrate the circulation of antimicrobial-resistant E. coli and C. jejuni variants among diarrheic calves and highlight the need for integrated phenotypic and molecular surveillance.