Oral Presentation The Prato Conference on the Pathogenesis of Bacterial Infections of Animals 2016

The effect of antimicrobial treatment strategies on selection of resistant bacteria and adaptation of the resistant bacteria to treatment (#15)

John Elmerdahl Olsen 1
  1. University of Copenhagen, Frederiksberg C, Denmark

Antimicrobial resistance is a global threat to human and animal health. Strategies to reduce the problem include improvement on current use of antimicrobials, increased effort to find new drugs, finding alternative approaches to antimicrobials, and improving diagnostic tools to avoid unnecessary treatments. Pig production is a major consumer of antimicrobials in many countries, mainly because flock medication is widely used in treatments. The first part of this presentation will compare effect of treatment and selection of antimicrobial resistant bacteria following flock treatment with oxytetracycline versus treatment of smaller groups of pigs and individual treatment of pigs against Lawsonia induced diarrhoea in post weaning pigs. Surprisingly, flock treatment did not results in significantly higher levels of tetracycline resistant coliform bacteria than treatment of smaller groups of pigs, and flock treatment was significantly better than treatment of smaller groups and individual pigs in reducing the number of affected animals. Rather than developing novel antimicrobials, attempts can be made to counteract the resistant organisms by targeting cell systems that are essential to express the resistant phenotype during treatment. In the second part of the presentation, the transcriptional response of an ESBL producing Escherichia coli strain to treatment with the cephalosporin drug cephalexin at therapeutic dose will be presented. Treatment resulted in significant changes in more than 200 biosynthesis and metabolic genes. The study hypothesized that targeting adaptive pathways during treatment could be used to prevent the resistant bacteria from growing in the presence of the drug, and indeed mutagenesis or chemical blocking of selected significantly regulated pathways was shown to results in significant reduction of resistance. Drugs, which specifically target adaptive pathways, may be given together with current antibiotics to tackle the problem with resistant bacteria.