Antimicrobial resistance in commensal Escherichia coli in veal calves is associated with antimicrobial drug use

The aim of this study was to determine the association between farm management factors, including antimicrobial drug usage, and resistance in commensal Escherichia coli isolates from the faeces of white veal calves. Ninety E. coli isolates from one pooled sample per farm (n=48) were tested for their phenotypical resistance against amoxicillin, tetracycline, cefotaxime, ciprofloxacin and trimethoprim/sulfamethoxazole (TMP/SMX). Logistic regression analysis revealed the following risk factors (P < 0.05); farmer wearing the same work clothes for several days [ciprofloxacin, odds ratio (OR) 2.6; tetracycline, OR 2.4], administration of trimethoprim-sulfonamide combinations (TMP/SMX, OR 3.0; amoxicillin, OR 3.1; tetracycline, OR 2.6), >= 0.3 animal daily dosage per production cycle (ADD/pc), quinolones (ciprofloxacin, OR 2.8), >= 1.3 ADD/pc, penicillins (ciprofloxacin, OR 3.3; tetracycline, OR 3.4), >40 ADD/pc, tetracyclines (tetracycline, OR 3.2) and >40 ADD/pc, tetracyclines (tetracycline, OR 13.1; amoxicillin, OR 6.5). In this study antimicrobial resistance in commensal E. coli was mainly associated with antimicrobial drug use.