title: Population and evolutionary dynamics of Shiga-toxin producing Escherichia coli O157 in a beef herd: A longitudinal study.
abstract: Shiga toxin producing Escherichia coli O157:H7 (STEC O157) is naturally found in the gastrointestinal tract of cattle and can cause severe disease in humans. There is limited understanding of the population dynamics and microevolution of STEC O157 at herd level. In this study, isolates from a closed beef herd of 23 cows were used to examine the population turnover in the herd. Of the nine STEC O157 clades previously described, clade 7 was found in 162 of the 169 isolates typed. Multiple locus variable number tandem repeat analysis (MLVA) differentiated 169 isolates into 33 unique MLVA types. Five predominant MLVA types were evident with most of the remaining types containing only a single isolate. MLVA data suggest that over time clonal replacement occurred within the herd. Genome sequencing of 18 selected isolates found that the isolates were divided into four lineages, representing four different 'clones' in the herd. Genome data confirmed clonal replacement over time and provided evidence of cross transmission of strains between cows. The findings enhanced our understanding of the population dynamics of STEC O157 in its natural host that will help developing effective control measures to prevent the spread of the pathogen to the human population.
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Meghan
authors.initials: M
authors.lastname: Jones
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Sophie
authors.initials: S
authors.lastname: Octavia
authors.affiliation: School of Animal and Veterinary Science, Charles Sturt University, Wagga Wagga, New South Wales, Australia.
authors.forename: Geraldine
authors.initials: G
authors.lastname: Lammers
authors.affiliation: School of Animal and Veterinary Science, Charles Sturt University, Wagga Wagga, New South Wales, Australia.
authors.forename: Jane
authors.initials: J
authors.lastname: Heller
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Ruiting
authors.initials: R
authors.lastname: Lan
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002417:Cattle; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology; D019453:Escherichia coli O157 / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D005260:Female; D000069196:Gastrointestinal Microbiome / Q000235:genetics*; D016680:Genome, Bacterial / Q000235:genetics*; D006801:Humans; D008137:Longitudinal Studies; D018598:Minisatellite Repeats / Q000235:genetics*; D058889:Molecular Typing / Q000379:methods*; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011157:Population Dynamics; D000069466:Red Meat / Q000382:microbiology; D022603:Shiga Toxins / Q000235:genetics / Q000378:metabolism
chemical_list: D022603:Shiga Toxins