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Title: Human contact with dogs and the risk of acquiring antimicrobial resistant and extended-spectrum β-lactamase-producing Escherichia coli
Author: Ormandy, E. E.
ISNI:       0000 0004 7428 5838
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2018
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The increasing global disease burden due to antimicrobial-resistant (AMR) infections is a significant public health concern. Multi-drug resistant (MDR) isolates, including those resistant to third generation cephalosporins (3GC), are of particular concern in human and veterinary medicine. Previous studies report faecal carriage of AMR E. coli in up to 63.0% of UK dogs. However, there is currently a paucity of data regarding community carriage rates AMR E. coli in UK human populations, particularly those with high levels of contact with dogs. The aims of this study were to determine the prevalence and risk factors for faecal carriage of AMR and extended-spectrum ß-lactamase (ESBL)-producing E. coli in humans working with dogs in multiple environments, and in-contact kennelled dogs. The study also aimed to characterise and compare isolates of human and canine origin. Two concurrent cross-sectional studies were undertaken collecting faecal samples from 229 human and 296 canine participants across 69 premises in the North of England. All E. coli isolates were subjected to antimicrobial susceptibility testing and phylogenetic grouping, while resistant isolates were also subjected to PCR assays in order to detect resistance genes. Isolates displaying ESBL, AmpC or MDR phenotypes were also subjected to whole genome sequencing. Mixed effect logistic regression models were utilised in order to assess risk factors for carriage of AMR E. coli using questionnaire-derived data. Faecal carriage of AMR E. coli was high in the human (68.7%) and canine (58.9%) populations sampled, with resistance to ampicillin, trimethoprim and tetracycline most prevalent. An increased prevalence of resistance to amoxyclav and 3GCs was noted in dogs (10.6% and 9.7%) when compared to humans (3.1% and 4.2%), while the prevalence of ESBL-producing E. coli was higher in humans (3.1%) than dogs (0.003%). Molecular characterisation of E. coli isolates indicated that in the canine population phylogroup B1 isolates predominated, while in humans B2 isolates were most prevalent. Multi-locus sequence typing identified a large number of sequence types (ST) indicating a high level of diversity, and, while the most prevalent STs varied between host species, many were identified in both humans and dogs. Numerous bla genes conferring resistance to 3GCs were identified in both species. In humans, blaCTX-M-15 was most prevalent (n=4), while in dogs blaCMY-2 predominated (n=23), and was commonly associated with IncI1 ST23 (n=10) plasmids. Potential intra-species transmission of 3GC-resistant and MDR E. coli between individuals was identified on multiple premises and of additional concern, was the potential transmission of a CMY-2-producing E. coli ST372 strain between host species on the same premises. Risk factors associated with each resistance outcome varied between host species, however, some patterns did emerge. Prior hospitalisation was identified as a risk factor for multiple resistance outcomes in both species, and contact with an owner working in a human hospital was a risk factor for 3GC resistance in dogs. The role of diet was also highlighted as a risk factor in both species; feeding of a raw food diet to dogs in particular was associated with multiple outcomes, including carriage of MDR E. coli. Additionally, contact with farm animals was associated with multiple outcomes in both species, while dogs with owners working in farming were additionally at increased risk of carriage of MDR E. coli. Interestingly, the effect of antimicrobial treatment was variable. Our findings indicate dogs may act as a reservoir of resistance determinants to in-contact humans, however transmission may be bidirectional. The potential role of dogs in the complex epidemiology of antimicrobial resistance alongside other healthcare, animal and environment-associated risk factors, highlights the need for multidisciplinary approaches to address this issue effectively.
Supervisor: Williams, Nicola ; Pinchbeck, Gina ; Dawson, Susan ; O'Brien, Sarah Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral