Effects of Subtherapeutic Administration of Antimicrobial Agents to Beef Cattle on the Prevalence of Antimicrobial Resistance in Campylobacter jejuni and Campylobacter hyointestinalis

Abstract

The influence of antimicrobial agents on the development of antimicrobial resistance (AMR) in Campylobacter isolates recovered from 300 beef cattle maintained in an experimental feedlot was monitored over a 315-day period (11 sample times). Groups of calves were assigned to one of the following antimicrobial treatments: chlortetracycline and sulfamethazine (CS), chlortetracycline alone (Ct), virginiamycin, monensin, tylosin phosphate, and no antimicrobial agent (i.e., control treatment). In total, 3,283 fecal samples were processed for campylobacters over the course of the experiment. Of the 2,052 bacterial isolates recovered, 92% were Campylobacter (1,518 were Campylobacter hyointestinalis and 380 were C. jejuni). None of the antimicrobial treatments decreased the isolation frequency of C. jejuni relative to the control treatment. In contrast, C. hyointestinalis was isolated less frequently from animals treated with CS and to a lesser extent from animals treated with Ct. The majority (>94%) of C. jejuni isolates were sensitive to ampicillin, erythromycin, and ciprofloxacin, but more isolates with resistance to tetracycline were recovered from animals fed Ct. All of the 1,500 isolates of C. hyointestinalis examined were sensitive to ciprofloxacin. In contrast, 11%, 10%, and 1% of these isolates were resistant to tetracycline, erythromycin, and ampicillin, respectively. The number of animals from which C. hyointestinalis isolates with resistance to erythromycin and tetracycline were recovered differed among the antimicrobial treatments. Only Ct administration increased the carriage rates of erythromycinresistant isolates of C. hyointestinalis, and the inclusion of CS in the diet increased the number of animals from which tetracycline-resistant isolates were recovered. The majority of C. hyointestinalis isolates with resistance to tetracycline were obtained from cohorts within a single pen, and most of these isolates were recovered from cattle during feeding of a forage-based diet as opposed to a grain-based diet. The findings of this study show that the subtherapeutic administration of tetracycline, alone and in combination with sulfamethazine, to feedlot cattle can select for the carriage of resistant strains of Campylobacter species. Considering the widespread use of in-feed antimicrobial agents and the high frequency of beef cattle that shed campylobacters, the development of AMR should be monitored as part of an on-going surveillance program.

Food Animals and Antimicrobials: Impacts on Human Health

“…Each animal feeding on an antibiotic becomes a "factory" for the production and subsequent dispersion of antibiotic-resistant bacteria. NTA uses are also clearly linked to the propagation of multidrug resistance (MDR), including resistance against drugs that were never used on the farm (10,52,59,60,92,107,111,132,141,153,154,164). The chronic use of a single antibiotic selects for resistance to multiple structurally unrelated antibiotics via linkage of genes on plasmids and transposons (111,143).…”

Changes in Tetracycline Susceptibility of Enteric Bacteria following Switching to Nonmedicated Milk Replacer for Dairy Calves

“…Studies have associated antimicrobial use with resistance in enteric pathogens on dairy farms (16,21,38,40,41), with various levels of resistance depending on the dosage of antimicrobial agents used (24), and declines in resistance after removing exposure to antimicrobial agents (21). However, some studies have found no difference in resistance between treated and untreated cattle (22,35).…”

Genomics-Based Molecular Epidemiology of Campylobacter jejuni Isolates from Feedlot Cattle and from People in Alberta, Canada

“…In that same year, campylobacteriosis was the most common (notifiable) bacterial, enteric disease, with a provincial rate of 36.1 cases for every 100,000 people (38a, 41). Because of the relatively high number of human cases and the large numbers of cattle on feed in Alberta, research into the role of feedlot cattle as Campylobacter reservoirs has been ongoing (15,(18)(19)(20)(21). Campylobacter jejuni is of public health significance as the most common Campylobacter species isolated from human cases (approximately 85%) (28).…”