Transit effect s on fecal Escherichia coli Ol57 prevalence and coliform concentrations in feedlot cattle.

Our objectives were to evaluate the effects of transportation and lairage on fecal shedding of Escherichia coli 0157 {E. coli 0157), total Escherichia coli, and total coliforms in feedlot cattle, and the rela-tionships between E. coli 0157 prevalence and total E. coli population. The study was a randomized complete block design with a split-plot including 2 treatments: a nontransported group, which remained in its pen at all times, and a transported group, which was transported for 1 h in a trailer and subsequently unloaded in a differ-ent pen. The experiment was repeated on 3 different days (blocking factor) with 20 steers/d (10 steers/treatment, 60 total). Fecal samples were taken pretransport (h 0) and after 4 and 28 h, lairage from freshly voided fecal pats were taken from each animal. One gram of feces was transferred to a PBS tube, serially diluted, and plated onto Petrifilm for enumeration of total coliforms. Another sample (1 g) was added to gram-negative broth contain-ing Cefixime, cefsulodin, and vancomycin, and subjected to immunomagnetic separation. Resulting beads were plated onto MacConkey agar with sorbitol, Cefixime, and tellurite. Nonsorbitol fermenting colonies were selected and tested for indole production and Ol 57 antigen agglu-tination. Results were confirmed using an API 20E kit. Prevalence of E. coli 0157 was transient across blocks. E. coli 0157 prevalence revealed no treatment x sam-pling time interaction (P = 0.179) or sampling time effect (P = 0.937), but a tendency for a treatment effect (P = 0.092). Numbers of E. coli and other coliforms did not change across blocks. No effect of treatment (P > 0.7) was observed on total E. coli concentrations or total coli-forms. However, tendencies for treatment x sampling time interactions were observed on both populations (P < 0.08), as well as a tendency for a sampling time effect on total E. coli (P = 0.087) and an effect on total coliforms (P = 0.004). Prevalence of E. coli 0157 was not correlated with the concentration of total E. coli (P = 0.954). Results suggest that shedding of E. coli 0157 and eolifonns can vary within a period of 29 h. Greater statis-tical power and pathogen quantification, as well as hide sampling and stress-related measurements, are needed to be able to conclude on the effects of transport stress on E. coli 0157 prevalence and the changes undergone in pathogen shedding patterns after transportation. [ABSTRACT FROM AUTHOR]