Effects of Therapeutic Ceftiofur Administration to Dairy Cattle on Escherichia coli Dynamics in the Intestinal Tract
- 15 November 2008
- journal article
- Published by American Society for Microbiology in Applied and Environmental Microbiology
- Vol. 74 (22), 6956-6962
- https://doi.org/10.1128/aem.01241-08
Abstract
The goal of this study was to follow ceftiofur-treated and untreated cattle in a normally functioning dairy to examine enteric Escherichia coli for changes in antibiotic resistance profiles and genetic diversity. Prior to treatment, all of the bacteria cultured from the cows were susceptible to ceftiofur. Ceftiofur-resistant E. coli was only isolated from treated cows during and immediately following the cessation of treatment, and the 12 bla CMY-2 -positive isolates clustered into two genetic groups. E. coli bacterial counts dropped significantly in the treated animals ( P < 0.027), reflecting a disappearance of the antibiotic-susceptible strains. The resistant bacterial population, however, did not increase in quantity within the treated cows; levels stayed low and were overtaken by a returning susceptible population. There was no difference in the genetic diversities of the E. coli between the treated and untreated cows prior to ceftiofur administration or after the susceptible population of E. coli returned in the treated cows. A cluster analysis of antibiotic susceptibility profiles resulted in six clusters, two of which were multidrug resistant and were comprised solely of isolates from the treated cows immediately following treatment. The antibiotic treatment provided a window to detect the presence of ceftiofur-resistant E. coli but did not appear to cause its emergence or result in its amplification. The finding of resistant isolates following antibiotic treatment is not sufficient to estimate the strength of selection pressure nor is it sufficient to demonstrate a causal link between antibiotic use and the emergence or amplification of resistance.Keywords
This publication has 37 references indexed in Scilit:
- Optimization of Analytical Parameters for Inferring Relationships among Escherichia coli Isolates from Repetitive-Element PCR by Maximizing Correspondence with Multilocus Sequence Typing DataApplied and Environmental Microbiology, 2006
- Use of a Nonmedicated Dietary Supplement Correlates with Increased Prevalence of Streptomycin-Sulfa-Tetracycline-Resistant Escherichia coli on a Dairy FarmApplied and Environmental Microbiology, 2006
- Molecular Epidemiology of Ceftiofur-Resistant Escherichia coli Isolates from Dairy CalvesApplied and Environmental Microbiology, 2006
- Variability in the Region Downstream of the bla CMY-2 β-Lactamase Gene in Escherichia coli and Salmonella enterica PlasmidsAntimicrobial Agents and Chemotherapy, 2006
- Antimicrobial Drug Resistance Genes Do Not Convey a Secondary Fitness Advantage to Calf-Adapted Escherichia coliApplied and Environmental Microbiology, 2006
- genalex 6: genetic analysis in Excel. Population genetic software for teaching and researchMolecular Ecology Notes, 2005
- β-Lactam Resistance andEnterobacteriaceae, United StatesEmerging Infectious Diseases, 2005
- Ceftriaxone-Resistant Salmonella Infection Acquired by a Child from CattleThe New England Journal of Medicine, 2000
- The ecology of Escherichia coli in calves reared as dairy‐cow replacementsJournal of Applied Bacteriology, 1985
- The ecology of Escherichia coli in market calves fed a milk‐substitute dietJournal of Applied Bacteriology, 1985