Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/29/2016
Publication Date: 6/16/2016
Citation: Kudva, I.T., Casey, T., Lippolis, J.D., Trachsel, J., Allen, H.K. 2016. Comparative analysis of Escherichia coli O157 growth and protein-expression, in vitro and in vivo, in rumen fluid of cattle [abstract]. American Society for Microbiology Microbe, June 16 - 20, 2016, Boston, Massachusetts. p. 567.
Technical Abstract: Cattle are the primary reservoirs for Escherichia coli O157 (O157), a Shiga toxin-producing E. coli, with potential for serious extraintestinal sequelae in humans. In a recent study (Kudva IT et al. BMC Microbiol. 2014; 14:48), we reported that when cultured in rumen fluid from dairy cattle on the maintenance diet (high in fiber), O157 expresses proteins involved in survival rather than those contributing to virulence. This observation was in contrast to the well-established expression of virulence factors by O157 during colonization of the human host. In the current study, we evaluated if similar results would be obtained when different O157 strains are grown, (i) in vitro in rumen fluid from animals on other diets usually provided to dairy cattle, and (ii) in vivo within the rumen of fistulated animals on the same diets, using a new method that not only allows such in vivo studies in the cattle rumen but also permits reuse of animals. Rumen-fistulated, dairy cattle were fed either the maintenance diet as reported previously, or a lactation diet (high in protein). Three different strains of O157 were studied: EDL 933, 86-24 and a super shed isolate SS-17. As expected, the two diets had differing influences on the ruminal pH and volatile fatty acid (VFA) profiles. The ruminal pH ranged from 6.2 - 7.0, with total VFA concentrations of 109 - 141 microM/ml, among animals fed the maintenance diet. On the other hand, animals fed the lactation diet had ruminal pH ranging between 5.14 – 6.0, and total VFA of 125 - 241 microM/ml. O157 strains demonstrated different growth patterns in these rumen fluids, after 48 h at 39degree C, in both the in vitro and in vivo assays. A greater reduction in O157 viable counts was observed in rumen fluid from, or rumen of, cattle fed the lactation diet compared to the maintenance diet. We are presently profiling the proteomes of O157 isolates recovered from the in vitro and in vivo assays, to obtain insights into mechanisms adapted by these O157 strains in rumen fluid with different compositions. Such data will be helpful in formulating effective therapeutic and/or diagnostic modalities to curtail O157 in cattle.