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Antimicrobial Use and Carriage of Antimicrobial-Resistant Escherichia Coli and Staphylococci in Dogs and Horses in the Community: Molecular Mechanisms of Resistance and Risk to Humans


Antimicrobial resistance is an increasing problem in both human and veterinary medicine. Many bacteria now have mechanisms of resistance to antimicrobials, which makes treatment difficult and these can also spread to other bacteria. The mechanisms of antimicrobial resistance vary for different bacteria and are mainly associated with having the presence of the antimicrobial in their environment. There is often a cost to the bacteria of having such resistance genes, however bacteria can adapt to negate such costs and maintain resistance in the absence of selection.
Antimicrobial usage may be associated with development of resistance, however the use of the antimicrobials may not necessarily be in the same species as the resistance develops. Furthermore antimicrobials used in animals and not in man may confer cross-resistance to antimicrobials used in human medicine. Therefore, this project aims to study the effect of using antimicrobials in companion animals and the impact this has on the development of antimicrobial resistance in bacteria from these animal species. Furthermore it will also investigate the mechanisms responsible for resistance and allow comparison with those found in human clinical isolates. This will also inform on any difficulties in treating companion animals with antimicrobials, where resistance is present and thereby have an impact on animal welfare. We will also investigate risk pathways for zoonotic transmission of antimicrobial resistant organisms/genes and evaluate the use of a risk assessment of the likely role antibacterial treatment in companion animals plays in terms of antibacterial resistance in humans.
Cross-sectional studies will be carried out on both dogs and horses for antibiotic resistant E. coli and staphylococci, recruited by veterinary surgeons. In addition faecal samples already collected from a previous DEFRA-funded study on dogs in a community, will be assessed for the prevalence of antimicrobial resistant E.coli. From both dogs and horses faecal samples will be collected for culture of antimicrobial resistant E.coli and determination of what antimicrobial resistance is present. In addition, nasal swabs will be collected for culture of antimicrobial resistant staphylococci, including identification of methicilllin resistance S.aureus (MRSA).Molecular characterisation of antimicrobial resistance will be determined and this will allow comparison with known mechanisms of resistance found in human bacterial isolates.
A survey to determine the use of antimicrobials in companion animal practice will be carried out. A questionnaire will be administered to veterinary surgeons to provide data on antimicrobials used, condition treated, dosage and duration of treatment. This information could be used to compile rational guidelines on the use of antimicrobials in companion animal practice.
Humans have frequent and close contact with dogs, horses and their faeces and therefore there is much opportunity for zoonotic spread of antimicrobial resistance. This study will determine risk pathways and evaulate a risk assessment framework for the zoonotic potential of antimicrobial resistant organisms/genes in companion animals. The risk pathways and risk assessment framework will provide a model for further studies of other zoonotic pathogens from companion animals. To date there is no published risk assessment framework available for companion animal zoonoses.
Objectives: <OL> <LI>
To determine prescribing practice of antimicrobials in companion animal medicine.
<LI> To estimate the prevalence of antimicrobial resistance in Escherichia coli in dogs in a community.
<LI> To estimate the prevalence of antimicrobial resistance in E. coli and staphylococci in dogs and horses nationwide (mainland UK).
<LI> To identify genes responsible for antimicrobial resistance by molecular characterisation of resistant isolates from dogs and horses.
<LI> To compare the genes responsible in companion animals with those prevalent in human clinical settings and their transferability.
<LI> To determine duration of shedding of organisms with antimicrobial resistance in both dogs and horses.
<LI> To identify risk pathways for the transmission of antimicrobial resistance between companion animals and humans, and to determine key data requirements and areas of specific uncertainty, and if deemed feasible the potential offered by quantitative and qualitative risk assessment.

University of Liverpool
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