Escherichia coli: - biofilms and the adulteration of fresh lettuce and antimicrobial resistance in a One Health Continuum

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dc.contributor.authorAdator, Emelia
dc.contributor.examiningcommitteeHouse, James (Food and Human Nutritional Sciences)en_US
dc.contributor.examiningcommitteeNadon, Celine (Medical Microbiology and Infectious Disease)en_US
dc.contributor.examiningcommitteeMcEwen, Scott (Population Medicine, University of Guelph)en_US
dc.contributor.supervisorNarvaez, Claudia (Food and Human Nutritional Sciences) McAllister,Tim (Food and Human Nutritional Sciences)en_US
dc.date.accessioned2020-08-20T13:48:48Z
dc.date.available2020-08-20T13:48:48Z
dc.date.copyright2020-08-14
dc.date.issued2020-08-14en_US
dc.date.submitted2020-08-14T15:25:04Zen_US
dc.date.submitted2020-08-19T20:57:55Zen_US
dc.degree.disciplineFood and Human Nutritional Sciencesen_US
dc.degree.levelDoctor of Philosophy (Ph.D.)en_US
dc.description.abstractBiofilm formation and antimicrobial resistance (AMR) posse serious food safety concerns. Bacteria AMR can be enhanced by biofilm formation. The WHO recently recommended a One Health approach to AMR surveillance due to the complexity of AMR occurrence and the two major pathways; (i) the environment and (ii) food by which AMR can arrive in humans. This thesis investigated the biofilm formation ability of the top seven Shiga toxigenic E. coli, their survival, and transfer from dry-surface biofilms to fresh lettuce at different times and temperatures using crystal violet assays. E. coli biofilms formed on polystyrene and stainless steel plates at 10°C were week biofilm producers. All STEC transferred viable cells (up to 6.35 log cfu/g) onto fresh lettuce after 2 minutes and were recovered from dry-surface biofilms on polystyrene and stainless steel plates after 30 days using enrichment. Results signify that STEC can potentially survive desiccation and subsequently serve as a source of contamination in processing environments. The thesis also investigated AMR along the One Health continuum using generic (n=663) and presumptive ESBL E. coli (ESBL-EC) (n=705) originating from beef production systems, municipal sewage treatment, and human clinical isolates. E. coli were characterized for phenotypic and genotypic AMR using antimicrobial susceptibility tests and PCRs. A subset of resistant ESBL-EC (n=162) was subjected to whole genome sequencing (WGS) and the presence of AMR genes, plasmids, integrative conjugative elements, virulence factors, multi-locus sequence, and serotypes were explored. Multidrug resistance ranged between MSewage (98.0%) and SStreams (61.4%) for presumptive ESBL-EC and between BProcessing (10.7%) and CFeces (45.1%) for generic E. coli. WGS corroborated phenotypic AMR, with tetracycline resistance determinants [tet(A), tet(B), tet(C), tet(M) and tet(32)] detected in cattle- (91.6%) and human-sourced ESBL-EC (87.3%) and β-lactams [blaTEM, blaCTX-M, blaOXA, blaLAP,blaSHV, blaEC, and blaCMY] detected in ESBL-EC from all sources (100%). WGS sensitivity to predict phenotypic AMR ranged between 93.2% and 100%. Comparative genomics identified distinct clusters for human and cattle-sourced isolates, with ST131 and ST244 being respectively predominant. Virulence genes identified included those involved with surface adhesion, biofilm formation, and hemolysis. Of all plasmids identified, 8/38 were often significantly higher in human isolates (P≤0.018). The niche-specific AMR, plasmids, virulence, and sequence/ serotype traits highlight the fact that although similar genetic factors occur across various segments of the continuum, presumptive ESBL-EC originating from beef cattle may not be responsible for recent human ESBL-EC infections. Elucidating the nature and dynamics of AMR along the One Health continuum is a first step that provides invaluable information for risk assessment and mitigation strategies targeted at AMR from farm-to-fork.en_US
dc.description.noteOctober 2020en_US
dc.identifier.urihttp://hdl.handle.net/1993/34879
dc.language.isoengen_US
dc.rightsopen accessen_US
dc.subjectFood microbiologyen_US
dc.subjectFood safetyen_US
dc.subjectAntimicrobial resistanceen_US
dc.subjectE. colien_US
dc.subjectBiofilmen_US
dc.subjectWhole genome sequencingen_US
dc.subjectComparative genomicsen_US
dc.subjectESBL E. colien_US
dc.subjectExtended-spectrum beta-lactamaseen_US
dc.titleEscherichia coli: - biofilms and the adulteration of fresh lettuce and antimicrobial resistance in a One Health Continuumen_US
dc.typedoctoral thesisen_US
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