Raw meat diets are a major risk factor for carriage of third-generation cephalosporin-resistant and multidrug-resistant E. coli by dogs in the UK

Abstract

Introduction: Raw-meat diets (RMD) for dogs, comprising unprocessed or non-heat-treated animal material, are increasingly popular. However, RMDs have been demonstrated to be contaminated with antimicrobial resistant (AMR) bacteria, and there is concern that such diets may pose a zoonotic disease risk. Additionally, dogs fed RMD may shed more AMR- fecal bacteria compared to those fed conventional cooked diets. Data from the UK remain limited; the present study investigated the presence of AMR-Escherichia coli in the feces of RMD and non-RMD (NRMD)-fed dogs in the UK, the E. coli AMR gene complement, and the lifestyle risk factors associated with AMR- E. coli carriage.

Methods: Fecal samples from UK-owned dogs (N = 193 RMD, N = 239 NRMD) and questionnaires discussing lifestyle factors, were obtained between October 2020-August 2021. Samples underwent culture and antimicrobial susceptibility testing to determine the presence of AMR-E. coli. Whole genome sequencing determined AMR gene carriage. Risk factors for the presence of AMR-E. coli were determined by multivariable modeling.

Results: RMD dogs carried significantly more fecal AMR E. coli (p < 0.001), including third-generation cephalosporin resistant, extended-spectrum beta-lactamase (ESBL) producing, and multidrug resistant isolates and multivariable modeling confirmed raw-meat diets to be a significant risk factor. The bla _CTX-M-15 gene was the most frequently identified bla _ESBL gene. The bla _CTX-M-55 and bla _SHV-66 genes were also prevalent and were only found in RMD dogs. The mobile colistin resistance gene, mcr-4 was identified in one ESBL-producing E. coli isolate from a NRMD-fed dog.

Conclusion: This study has shown that dogs fed RMD in the UK are significantly more likely to shed E. coli which is resistant to highest priority critically important antibiotics, and multidrug resistant E. coli, than dogs fed NRMD. Additionally, AMR-E. coli isolates from RMD-fed dogs harbor multiple, diverse, and novel AMR genes. Therefore, provision of RMD to dogs could pose an important potential threat to human and animal health, especially given the close nature of the relationship many owners share with their pets. Awareness of these findings should be shared with pet owners, veterinary and medical professionals, pet food manufacturers and public health to mitigate potential risks.

Keywords: AMR; E. coli; One Health; carriage; dog; raw meat diet.

FIGURE 1

ESBL, pAmpC and quinolone resistance associated qnr genes associated with each isolate which underwent whole genome sequencing, alongside the sequence type (ST) and clonal complex (CC) identified and phenotypic resistance demonstrated via disk diffusion. For the “raw” column, a yellow box denotes a raw-fed dog isolate, whereas a blue box denotes a non-raw fed dog isolate. For the genes, a colored box indicates presence of a gene. For the phenotypic resistance, a black box denotes a resistance, and a gray box denotes susceptible. Although amikacin, tigecycline and meropenem were all tested via disk diffusion, no resistance was observed, and they have been omitted from this figure. *Amp, ampicillin; AmxC, amoxycillin-clavulanate; Cip, ciprofloxacin; TMS, trimethoprim-sulphamethoxazole; Ctx, cefotaxime; Ctz, ceftazidime; MDR, multidrug resistance. ^inhibitor-resistant genes.

FIGURE 2

Phylogenetic tree demonstrating the eBURST groups and sequence types (ST) present, and their relationships, for E. coli isolates which underwent whole genome sequencing. For the “group” column, a pink box denotes raw-fed, blue denotes non-raw-fed isolate.