Analysis of Canine Small Intestinal and Fecal Microbiota Prevention of Ampicillin-induced Changes with Oral β-lactamase

Background: The intestinal microbiota affects many physiological and immunological functions of the body and is closely connected to the homeostasis and health status of an individual. Due to difficulties in obtaining samples from the intestine and studying complex microbial populations the knowledge of the composition, dynamics and metabolic potential of microbial populations in the upper gut is limited. Antimicrobials may disrupt the balance of the microbiota by causing quantitative and qualitative changes such as emergence and enrichment of antibioticresistant populations, and decrease in colonisation resistance against pathogens. The aims of this study were to analyse cultivable jejunal microbiota of a dog in detail and compare it to faecal findings, and to evaluate the ability of oral β-lactamase administration, targeted to degrade intestinal ampicillin residues, to prevent ampicillin-induced changes in the intestinal microbiota. Material and methods: Jejunal and faecal samples were obtained from healthy laboratory beagles with permanent jejunal fistula randomised into 3 treatment groups receiving ampicillin, ampicillin + β-lactamase or placebo. Samples were collected before, during and after the treatment and analysed using bacterial culture and TGGE (temperature-gradient gel electrophoresis) for total bacterial counts and composition of the dominant microbiota. Susceptibility testing and PCR for detection of TEM gene were the methods for monitoring resistance rates. In addition, jejunal and serum ampicillin concentrations were determined. Results: The relative quantities of predominant bacterial groups, proportion of anaerobes, intraand inter-individual species variety and stability of the microbiota differed significantly between the jejunum and faeces. Oral β-lactamase inhibited the effects of ampicillin, monitored as significant differences in resistance rates and