Gastrointestinal Tract Location of Escherichia coli O157:H7 in Ruminants

Abstract

Experimentally inoculated sheep and cattle were used as models of natural ruminant infection to investigate the pattern of Escherichia coli O157:H7 shedding and gastrointestinal tract (GIT) location. Eighteen forage-fed cattle were orally inoculated with E. coli O157:H7, and fecal samples were cultured for the bacteria. Three distinct patterns of shedding were observed: 1 month, 1 week, and 2 months or more. Similar patterns were confirmed among 29 forage-fed sheep and four cannulated steers. To identify the GIT location of E. coli O157:H7, sheep were sacrificed at weekly intervals postinoculation and tissue and digesta cultures were taken from the rumen, abomasum, duodenum, lower ileum, cecum, ascending colon, descending colon, and rectum. E. coli O157:H7 was most prevalent in the lower GIT digesta, specifically the cecum, colon, and feces. The bacteria were only inconsistently cultured from tissue samples and only during the first week postinoculation. These results were supported in studies of four Angus steers with cannulae inserted into both the rumen and duodenum. After the steers were inoculated, ruminal, duodenal, and fecal samples were cultured periodically over the course of the infection. The predominant location of E. coli O157:H7 persistence was the lower GIT. E. coli O157:H7 was rarely cultured from the rumen or duodenum after the first week postinoculation, and this did not predict if animals went on to shed the bacteria for 1 week or 1 month. These findings suggest the colon as the site for E. coli O157:H7 persistence and proliferation in mature ruminant animals.For many years it has been known that healthy ruminants transiently harbor the human pathogen Escherichia coli O157:H7 in their gastrointestinal tract; however, the conditions that lead to its acquisition, persistence, and clearance from that site are not clearly understood (18,30). Elucidating the relationship between cattle and E. coli O157:H7 may impact the development of interventions to curb its presence in ruminants and thereby reduce the incidence of human infections with this pathogen.The hallmark of human disease with E. coli O157:H7 is a hemorrhagic colitis that is most often self-limiting (2, 18). However, among reported outbreaks, as many as 25% of infected individuals have been hospitalized, 6% have developed life-threatening sequelae, the hemolytic uremic syndrome, and 1% have died from their infection. For children infections are even more severe, with 5 to 10% progressing to hemolytic uremic syndrome and a 3 to 5% mortality rate (2, 6, 18). E. coli O157:H7 is transmitted by ingestion of contaminated bovine food products, contaminated drinking water or fruit juice, contact with contaminated recreation water or culture-positive animals, and in rare cases, human-to-human transmission via the fecal-oral route (2,3,18,24).Although healthy cattle (5, 9, 15, 21, 37), sheep (9, 26, 28), deer (16, 34), and goats (9, 32) have been shown to transiently harbor E. coli O157:H7 naturally, cattle are the main source of human infections ...

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.…”

Microbiological quality of organic vegetables produced in soil treated with different types of manure and mineral fertilizer

“…This concern is directed to Salmonella spp. (24,27,40,47,49) and E. coli O157:H7, because cattle is its main reservoir, explaining the risk of transmission by manure (22,34,43,50).…”

Escherichia coli O157:H7-secreted cytotoxins are toxic to enterocytes and increase Escherichia coli O157:H7 colonization of jejunum and descending colon in cattle

“…Challenged older calves can have transient watery diarrhea or have no symptoms, as observed for mature cattle (Cray and Moon 1995;Brown et al 1997). EHEC O157:H7 has been isolated from the small and large intestine of older calves and mature cattle but not necessarily associated with A/E lesions (Cray and Moon 1995;Brown et al 1997;Grauke et al 2002;Naylor et al 2003;van Baale et al 2004). The current model for EHEC O157:H7 colonization in cattle suggests that the lymphoid-follicle dense mucosa in the terminal rectum is the primary colonization site and it is this colonization that is responsible for persistent shedding (Naylor et al 2003Sheng et al 2004Sheng et al , 2006Lim et al 2007).…”