Journal article
Antimicrobial Drug Resistance Genes Do Not Convey a Secondary Fitness Advantage to Calf-Adapted Escherichia coli
Applied and environmental microbiology, Vol.72(1), pp.443-448
01/2006
Handle:
https://hdl.handle.net/2376/107246
PMCID: PMC1352232
PMID: 16391076
Abstract
Maintenance of antimicrobial drug resistance in bacteria can be influenced by factors unrelated to direct selection pressure such as close linkage to other selectively advantageous genes and secondary advantage conveyed by antimicrobial resistance genes in the absence of drug selection. Our previous trials at a dairy showed that the maintenance of the antimicrobial resistance genes is not influenced by specific antimicrobial selection and that the most prevalent antimicrobial resistance phenotype of
Escherichia coli
is specifically selected for in young calves. In this paper we examine the role of secondary advantages conveyed by antimicrobial resistance genes. We tested antimicrobial-susceptible null mutant strains for their ability to compete with their progenitor strains in vitro and in vivo. The null mutant strains were generated by selection for spontaneous loss of resistance genes in broth supplemented with fusaric acid or nickel chloride. On average, the null mutant strains were as competitive as the progenitor strains in vitro and in newborn calves (in vivo). Inoculation of newborn calves at the dairy with antimicrobial-susceptible strains of
E. coli
did not impact the prevalence of antimicrobial-resistant
E. coli
. Our results demonstrate that the antimicrobial resistance genes are not responsible for the greater fitness advantage of antimicrobial-resistant
E. coli
in calves, but the farm environment and the diet clearly exert critical selective pressures responsible for the maintenance of antimicrobial resistance genes. Our current hypothesis is that the antimicrobial resistance genes are linked to other genes responsible for differential fitness in dairy calves.
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Details
- Title
- Antimicrobial Drug Resistance Genes Do Not Convey a Secondary Fitness Advantage to Calf-Adapted Escherichia coli
- Creators
- Artashes R Khachatryan - Department of Veterinary Microbiology and PathologyDale D Hancock - Department of Veterinary Microbiology and PathologyThomas E Besser - Department of Veterinary Microbiology and PathologyDouglas R Call - Department of Veterinary Microbiology and Pathology
- Publication Details
- Applied and environmental microbiology, Vol.72(1), pp.443-448
- Academic Unit
- Veterinary Microbiology and Pathology, Department of; Paul G. Allen School for Global Animal Health
- Publisher
- American Society for Microbiology
- Identifiers
- 99900547024901842
- Language
- English
- Resource Type
- Journal article