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<jats:title>ABSTRACT</jats:title> <jats:p> To get insights into the temporal pattern of commensal <jats:named-content content-type="genus-species">Escherichia coli</jats:named-content> populations, we sampled the feces of four healthy cows from the same herd in the Hwange District of Zimbabwe daily over 25 days. The cows had not received antibiotic treatment during the previous 3 months. We performed viable <jats:named-content content-type="genus-species">E. coli</jats:named-content> counts and characterized the 326 isolates originating from the 98 stool samples at a clonal level, screened them for <jats:italic>stx</jats:italic> and <jats:italic>eae</jats:italic> genes, and tested them for their antibiotic susceptibilities. We observed that <jats:named-content content-type="genus-species">E. coli</jats:named-content> counts and dominant clones were different among cows, and very few clones were shared. No clone was shared by three or four cows. Clone richness and evenness were not different between cows. Within each host, the variability in the <jats:named-content content-type="genus-species">E. coli</jats:named-content> count was evidenced between days, and no clone was found to be dominant during the entire sampling period, suggesting the existence of clonal interference. Dominant clones tended to persist longer than subdominant ones and were mainly from phylogenetic groups A and B1. Five <jats:named-content content-type="genus-species">E. coli</jats:named-content> clones were found to contain both the <jats:italic>stx</jats:italic> <jats:sub>1</jats:sub> and <jats:italic>stx</jats:italic> <jats:sub>2</jats:sub> genes, representing 6.3% of the studied isolates. All cows harbored at least one Shiga toxin-producing <jats:named-content content-type="genus-species">E. coli</jats:named-content> (STEC) strain. Resistance to tetracycline, penicillins, trimethoprim, and sulfonamides was rare and observed in three clones that were shed at low levels in two cows. This study highlights the fact that the commensal <jats:named-content content-type="genus-species">E. coli</jats:named-content> population, including the STEC population, is host specific, is highly dynamic over a short time frame, and rarely carries antibiotic resistance determinants in the absence of antibiotic treatment. </jats:p> <jats:p> <jats:bold>IMPORTANCE</jats:bold> The literature about the dynamics of commensal <jats:named-content content-type="genus-species">Escherichia coli</jats:named-content> populations is very scarce. Over 25 days, we followed the total <jats:named-content content-type="genus-species">E. coli</jats:named-content> counts daily and characterized the sampled clones in the feces of four cows from the same herd living in the Hwange District of Zimbabwe. This study deals with the day-to-day dynamics of both quantitative and qualitative aspects of <jats:named-content content-type="genus-species">E. coli</jats:named-content> commensal populations, with a focus on both Shiga toxin-producing <jats:named-content content-type="genus-species">E. coli</jats:named-content> and antibiotic-resistant <jats:named-content content-type="genus-species">E. coli</jats:named-content> strains. We show that the structure of these commensal populations was highly specific to the host, even though the cows ate and roamed together, and was highly dynamic between days. Such data are of importance to understand the ecological forces that drive the dynamics of the emergence of <jats:named-content content-type="genus-species">E. coli</jats:named-content> clones of particular interest within the gastrointestinal tract and their transmission between hosts. </jats:p>
- 出版日期2017-7
- 单位常州工学院
