Doctoral Thesis
Investigating pet dogs as a potential source of antimicrobial resistant enteric bacteria and parasites that may impact on human health
Doctor of Philosophy (PhD), Murdoch University
2024
Abstract
Australia, with over six million dogs residing in households as of 2021, has one of the highest pet ownership rates globally. Dogs often share close living spaces with humans, creating potential health risks, such as the transmission of resistant bacteria and zoonotic parasites, given dogs' role as reservoirs for these microorganisms.
This project aimed to isolate and characterize antimicrobial-resistant Escherichia coli and enterococci, significant to human medicine, from non-clinical samples in Western Australia's companion dog community. Ciprofloxacin-resistant E. coli were found in 5.8% of the dogs, along with antimicrobial resistant enterococci detected in low to moderate resistance to other antimicrobials, except oxazolidinone and streptogramin. Genotyping revealed emerging multidrug-resistant E. coli strains with critical importance antibiotic (CIA) resistance, indicating that healthy dogs can carry and potentially spread pandemic strains resistant to vital human medicines. Sequence typing of E. faecium showed a diverse range of sequence types, with human-associated virulence genes detected in all isolates, suggesting bacterial sharing between humans and dogs.
This thesis also aimed to assess parasite carriage and prevalence in Western Australian puppies and pet dogs. Parasites were present in 50.9% of puppies, with Ancylostoma spp., Toxocara spp., Cystoisospora spp., and Giardia spp. detected, while juvenile and adult dogs only carried protozoan parasites (18%), with G. duodenalis persisting across all groups. Genotyping Giardia-positive samples identified zoonotic assemblages in two puppies and one community dog, highlighting significant public health implications and the need for effective anti-protozoan drugs to prevent parasitism spread.
The final aim was to identify novel anti-giardial compounds from a library of robenidine analogues, aiming for increased potency and selectivity for treating G. duodenalis in dogs. A new class of anti-protozoal agents, derived from this unique chemical library, showed improved in-vitro anti-giardial activity compared to metronidazole. Out of 40 robenidine analogues screened, four exhibited superior activity and were selected for further evaluation. The lead analogue emerged as a promising compound with high potency and selectivity, without existing resistance.
Overall, this thesis contributes to understanding of the carriage of potentially zoonotic antimicrobial resistant bacteria, E. coli and enterococci, and gastrointestinal parasites by domestic dogs in Western Australia. Additionally, a proposed solution to a lack of effective Giardia treatments was investigated through evaluating the efficacy and toxicity of a novel class of antiprotozoal agents.
Details
- Title
- Investigating pet dogs as a potential source of antimicrobial resistant enteric bacteria and parasites that may impact on human health
- Authors/Creators
- Breanna R Knight
- Contributors
- Amanda Ash (Supervisor) - Murdoch University, Centre for Biosecurity and One HealthSam Abraham (Supervisor) - Murdoch University, Centre for Biosecurity and One HealthUna Ryan (Supervisor) - Murdoch University, Centre for Biosecurity and One HealthMark O'Dea (Supervisor)
- Awarding Institution
- Murdoch University; Doctor of Philosophy (PhD)
- Identifiers
- 991005703769407891
- Murdoch Affiliation
- Centre for Biosecurity and One Health; School of Medical, Molecular and Forensic Sciences
- Resource Type
- Doctoral Thesis
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