Rectoanal Junction Colonization of Feedlot Cattle by Escherichia coli O157:H7 and Its Association with Supershedders and Excretion Dynamics

Abstract

Feedlot cattle were observed for fecal excretion of and rectoanal junction (RAJ) colonization with Escherichia coli O157:H7 to identify potential "supershedders." RAJ colonization and fecal excretion prevalences were correlated, and E. coli O157:H7 prevalences and counts were significantly greater for RAJ samples. Based on a comparison of RAJ and fecal ratios of E. coli O157:H7/E. coli counts, the RAJ appears to be preferentially colonized by the O157:H7 serotype. Five supershedders were identified based on persistent colonization with high concentrations of E. coli O157:H7. Cattle copenned with supershedders had significantly greater mean pen E. coli O157:H7 RAJ and fecal prevalences than noncopenned cattle. Cumulative fecal E. coli O157:H7 excretion was also significantly higher for pens housing a supershedder. E. coli O157:H7/E. coli count ratios were higher for supershedders than for other cattle, indicating greater proportional colonization. Pulsed-field gel electrophoresis analysis demonstrated that isolates from supershedders and copenned cattle were highly related. Cattle that remained negative for E. coli O157:H7 throughout sampling were five times more likely to have been in a pen that did not house a supershedder. The data from this study support an association between levels of fecal excretion of E. coli O157:H7 and RAJ colonization in pens of feedlot cattle and suggest that the presence of supershedders influences group-level excretion parameters. An improved understanding of individual and population transmission dynamics of E. coli O157:H7 can be used to develop preslaughter-and slaughter-level interventions that reduce contamination of the food chain.

Climate, lactation, and treatment factors influence faecal shedding ofEscherichia coliO157 pathotypes in dairy cows

“…Although studies to date have not assessed aEPEC prevalence, other studies of stx and O157:H7 dairy prevalence have shown both higher (72·7%, 11·1-32·3%) [15,18] and lower (1%) levels [10]. Importantly, high-shedding cattle have been hypothesized to influence herd EHEC propagation, and only one was observed in the current study [21,22]. To date, this is the first assessment of EHEC prevalence on dairies in the Rocky Mountain biome, so it is possible that lower shedding prevalence and measured outcomes may be inherent to the particular environment studied.…”

“…Importantly, those animals shedding high quantities of the pathogen ('high-shedders'; >10 3 -10 4 c.f.u./g faeces) may account for the majority of O157 contamination within a herd, increasing animal-to-animal transmission and risk of food chain contamination [18,21,22]. When classifying cows based on O157 shedding magnitude vs. positive shedding alone, outcomes for risk factor analyses can become altered [17].…”

Naturally resident and exogenously applied T4-like and T5-like bacteriophages can reduceEscherichia coliO157

“…38,39 These initial studies centered on bovine ruminal phages, but more recent O157:H7 phage research has moved to the recto-anal junction, the demonstrated major site of colonization in cattle. 15,40 Much less is known about O157:H7 colonization in sheep but the data suggests that it attaches more widely, including in the colon and rectum. [41][42][43] During our studies we found that half of the members of a single sheep flock carried the same new O157:H7-infecting phage, CEV2.…”

Recent Advances in Understanding Enteric Pathogenic Escherichia coli

“…A study in Scotland showed that cattle feces can contain from 100 to over 10 6 CFU of STEC O157:H7 per gram of feces (213). Increased shedding was associated with STEC mucosal colonization at the rectoanal junction (213,214). High-level shedding has implications for within-herd and between-farm transmission, as well as direct-contact and potential environmental exposure of humans, and has been discussed in more detail by Chase-Topping et al (215).…”