Emerging antimicrobial resistance against fluorochinolones and cephalosporins with public health relevance in commensal e.coli from animals and food in Germany

Resistance to antimicrobials in zoonotic bacteria and commensals is of special concern since this may compromise the effective treatment of infections in humans. To assess these risks and to identify factors of major impact, a systematic monitoring approach was established in Germany covering each of the major food production chains within a 3-year interval. All isolates were tested using the broth dilution method according to NCCLS/CLSI standards M31-A3 and minimum inhibitory concentrations were evaluated according to epidemiological cut-off values as published by EUCAST. Within the years 2009 and 2010, 3,802 E.coli isolates could be collected, covering primary production, animals at slaughterhouses and animal derived food at retail level. Whereas the majority of isolates from laying hens and dairy cattle were susceptible to the 14 antimicrobials tested, most isolates from broilers, turkeys, veal calves, chicken meat and turkey meat were resistant to at least one antimicrobial class. Most of these isolates were even resistant to several antimicrobial classes. Besides resistance to the commonly used antimicrobial classes, e.g. sulphonamides and tetracyclines, resistance to (fluoro)quinolones and cephalosporins was frequently observed. Resistance rates to ciprofloxacin, the fluoroquinolone tested, were highest in broilers and chicken meat, ranging between 43% and 54% resistant isolates. In turkeys and turkey meat, ciprofloxacin resistance was slightly lower, ranging between 30% and 34%. In the veal production chain, resistance to ciprofloxacin decreased markedly from 42% in veal calves tested at primary production, to 13% in calves tested at slaughterhouses and 4% in veal sampled at retail. In contrast, resistance rates to (fluoro)quinolones in E.coli isolates from laying hens, dairy cattle and pork were below 10%. Resistance to ceftazidime, a 3¶rd generation cephalosporins was observed in isolates from all production chains studied but till now in a low level. Highest rates could be observed in broilers, where an increase from 5.9% to 13.5% was observed from 2009 to 2010 and chicken meat (6.2%). The observed resistance levels to (fluoro)quinolones and cephalosporins in commensal E.coli isolates are of concern since these are critically important antimicrobials in human medicine. The emerging pattern warrants close monitoring and regular assessment. Together with continuous monitoring of the antimicrobial usage, this may allow for assessing and adapting management strategies continuously.