Abstract
The aim of this study was to investigate the relationship between antimicrobial use and the occurrence of antimicrobial resistance in the digestive and respiratory tract in three different production systems of food producing animals. A longitudinal study was set up in 25 Belgian bovine herds (10 dairy, 10 beef, and 5 veal herds) for a 2 year monitoring of antimicrobial susceptibilities in E. coli and Pasteurellaceae retrieved from the rectum and the nasal cavity, respectively. During the first year of observation, the antimicrobial use was prospectively recorded on 15 of these farms (5 of each production type) and transformed into the treatment incidences according to the (animal) defined daily dose (TIADD) and (actually) used daily dose (TIUDD). Antimicrobial resistance rates of 4,174 E. coli (all herds) and 474 Pasteurellaceae (beef and veal herds only) isolates for 12 antimicrobial agents demonstrated large differences between intensively reared veal calves (abundant and inconstant) and more extensively reared dairy and beef cattle (sparse and relatively stable). Using linear mixed effect models, a strong relation was found between antimicrobial treatment incidences and resistance profiles of 1,639 E. coli strains (p<0.0001) and 309 Pasteurellaceae (p≤0.012). These results indicate that a high antimicrobial selection pressure, here found to be represented by low dosages of oral prophylactic and therapeutic group medication, converts not only the commensal microbiota from the digestive tract but also the opportunistic pathogenic bacteria in the respiratory tract into reservoirs of multi-resistance.
Highlights
Associations between antimicrobial use and the prevalence of resistance in commensal faecal E. coli of cattle have been documented [1,2,3] but that detailed records on the antimicrobial regimens are limited. Such detailed records retrieved from swine production have allowed to show that many applied antimicrobial regimens deviate from leaflet instructions [4], which on their turn influence the occurrence of antimicrobial resistance in faecal Enterobacteriaceae [5]
Detailed data on antimicrobial use by route of administration for the first year of the study period in the 5 dairy and the 5 beef farms, and the average of the total production cycle (6 months) in the 5 veal calf farms are presented in Tables 2 to 4
The antimicrobial use was monitored in bovine herds using a multi-centre approach and an intensive sample strategy of the digestive and respiratory tract
Summary
Associations between antimicrobial use and the prevalence of resistance in commensal faecal E. coli of cattle have been documented [1,2,3] but that detailed records on the antimicrobial regimens (e.g. dose) are limited Such detailed records retrieved from swine production have allowed to show that many applied antimicrobial regimens deviate from leaflet instructions [4], which on their turn influence the occurrence of antimicrobial resistance in faecal Enterobacteriaceae [5]. Large variations in antimicrobial resistance profiles of Pasteurellaceae between different bovine herds complicate empirical antimicrobial therapy of bovine respiratory disease [6,7] Inclusion of these opportunistic pathogenic bacteria in studies exploring relationships with antimicrobial use might aid to explain different stakeholders of the clinical relevance of antimicrobial resistance
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