The influence of the antimicrobial use in the resistance data on clinical and non-clinical isolates from broilers and turkeys in Germany

Antimicrobial use (AMU) is a main driver of antimicrobial resistance (AMR), one of the major public health concerns in the human and animal sectors. However, it is frequently difficult to demonstrate this association as AMR is also influenced by many factors. Surveillance and monitoring systems on AMU and AMR are essential pillars for global, regional, and national strategies against AMR to control and assess the trends. German data on AMR in clinical and non-clinical E. coli isolates together with usage data (based on the German unit therapy frequency) in broilers and turkeys were collected from monitoring systems between 2014 and 2017. Resistance had been determined using broth microdilution and interpreting the minimum inhibition concentrations according to the EUCAST epidemiological cut off values. The purpose of this work is to find associations between AMU and AMR. Logistic regression analyses were performed to assess the association between the AMU and the dependent variable (AMR) for the antimicrobial panel overlap between the monitoring systems for clinical and non-clinical isolates (ampicillin, ciprofloxacin, colistin, cefotaxime, gentamicin, nalidixic acid tetracycline). A negative association between AMU and AMR was shown to ciprofloxacin and nalidixic acid in non-clinical isolates from broilers. In turkeys, positive associations were found to nalidixic acid and tetracycline in non-clinical isolates and to tetracycline in clinical isolates. Cefotaxime resistance was low in isolates from broilers and turkeys which is in line with cephalosporins not being licensed for use in poultry. In summary, we found some associations of AMU and AMR in E. coli isolates from broilers and turkeys.This study indicates that further data analyses over longer time intervals are required to assess the long-term effects of changes in AMU on the prevalence of AMR.