Biological properties of acute intestinal bacterial infection agents in calves and their antibiotic resistance

The article presents the results of a study of morphological, cultural and antigenic properties and antibiotic resistance of the main bacterial pathogens causing acute intestinal infections in calves: Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis. Samples from sick and dead calves from farms in the Krasnodar Kray served as the study material. The aim of the study was to investigate morphological, cultural and antigenic properties of bacterial pathogens causing acute intestinal infections in calves, as well as their antimicrobial resistance. The study used classical bacteriological methods: Gram staining, an O-serum agglutination test and mass spectrometry. Sensitivity to 11 antibiotics from 9 groups was determined using the disk diffusion method. Seven E. coli strains belonging to serogroups O4, O137, O1, O86, O2 and O115 were isolated during the study, as well as one isolate each of P. aeruginosa and E. faecalis. E. coli were found to be lactose-positive and exhibit α-hemolysis on blood agar. P. aeruginosa produces a blue-green pigment, shows characteristic growth with a surface pellicle and exhibits β-hemolysis. E. faecalis forms dark red colonies on enterococcal agar and γ- hemolysis on blood agar. During assessment of antibiotic resistance revealed that 43% of E. coli strains were resistant to all 11 drugs tested. Partial susceptibility was observed only to fluoroquinolones (levofloxacin and ciprofloxacin). P. aeruginosa was susceptible to gentamicin, levofloxacin and ciprofloxacin; E. faecalis was susceptible to vancomycin, gentamicin and ciprofloxacin. Obtained data confirm the necessity for continuous antibiotic susceptibility monitoring and a review of treatment regimens when treating bacterial intestinal infections in calves.