Escherichia coli O157:H7-persistence studies in experimentally infected chickens and pigs

Escherichia coli O157:H7, first implicated in human illness in 1982, is an emerging food borne pathogen currently accounting for 74,000 cases of illness in the United States which manifests itself as diarrhea illness, hemorrhagic colitis and in extreme cases hemolytic uremic syndrome, a severe complication of the disease seen in approximately 10% of infections which can lead to death. Beef products are most often implicated as sources for infections and studies have found carriage rates up to 28% for normal healthy cattle, with herd prevalence from 22-100%. Although several ruminant species have been implicated in outbreaks of illness, the role of other food production animals in the spread of the disease is unclear. Included here are experimental studies conducted to determine the ability of chickens and pigs to become persistently infected with E. coli O157:H7 and the possibility of these animals becoming potential reservoirs. Broiler chickens and feeder pigs were inoculated with five E. coli strains. The inoculum included two Shigatoxigenic E. coli (STEC) O157:H7 strains, two enterotoxigenic E. coli (ETEC) strains and one enteropathogenic E. coli (EPEC) strain. A high dose inoculum with all five strains at approximately 1010 cfu/animal and a low dose inoculum with the STEC strains at approximately 107 cfu/animal and the EPEC and ETEC strains remaining at approximately 1010 cfu/animal were used. All of the strains persisted in the feces of some chickens given the high dose inoculum at two weeks post inoculation (pi). However, none of the strains persisted in the alimentary tracts of chickens at two months. In contrast to the results with chickens, the STEC strains persisted in the alimentary tracts of some pigs at two months pi following inoculation with both the high and low dose inocula. When all strains were given at approximately 1010 cfu (high dose inoculum) the STEC strains persisted in greater numbers and in more pigs than did the other strains. The results of this study demonstrated that persistent ([Greater than or equal to symbol]2 months) E. coli O157:H7 infections can occur in pigs. These findings were similar to those reported from sheep inoculated with the same set of E. coli strains

Colonization and Transmission of Escherichia Coli O157:H7 in Swine

Escherichia coli O157:H7 and other serogroups of Shiga toxin-producing E.coli (STEC) have emerged over the last several decades as a significant cause of food-borne illness in the United States. Approximately 5-10% of people clinically infected by these bacteria develop a systemic disease, hemolytic uremic syndrome, which has a fatality rate of approximately 5%. The Centers for Disease Control estimates that STEC cause some 110,000 illnesses and 90 deaths annually in the United States (Mead et al. 1999). In addition, the economic consequences of recalling large lots of food for public health reasons are significant. Cattle are considered to be the primary reservoir for STEC. Depending on the season, the methods used for bacterial culture and the age of the animals, the prevalence of E. coli O157:H7 in U.S. cattle ranges from 2-28% (Hancock et al. 1994; Elder et al. 2000). E.coli O157:H7 has also been recovered from other ruminants such as sheep (Kudva et al. 1996) and deer (Keene et al. 1997; Sargeant et al. 1999)

Intervention with Shiga Toxin (Stx) Antibody after Infection by Stx-Producing Escherichia coli

Shiga toxins (Stxs) produced by Escherichia coli (STEC) cause systemic vascular damage, manifested as hemolytic uremic syndrome in humans and as edema disease in pigs. Edema disease, a naturally occurring disease of pigs, was used to determine whether Stx antibodies, administered after infection and after the onset of Stx production, could prevent the systemic vascular damage and clinical disease caused by Stxs. A total of 119 STEC-infected pigs were treated with low, medium, or high doses of Stx antibody or with placebo. After inoculation with STEC, antibodies or placebo was injected intraperitoneally at 2 days postinoculation (DPI; low dose) or 4 DPI (medium and high doses). Edema disease was prevented with the low- and high-dose Stx antibody treatments administered at 2 and 4 DPI, respectively. Highdose antibody treatment also reduced the incidence and extent of vascular lesions. The degree of protection depended on the dose of antibody and the time of administration

Escherichia coli O157:H7-persistence studies in experimentally infected chickens and pigs

Escherichia coli O157:H7, first implicated in human illness in 1982, is an emerging food borne pathogen currently accounting for 74,000 cases of illness in the United States which manifests itself as diarrhea illness, hemorrhagic colitis and in extreme cases hemolytic uremic syndrome, a severe complication of the disease seen in approximately 10% of infections which can lead to death. Beef products are most often implicated as sources for infections and studies have found carriage rates up to 28% for normal healthy cattle, with herd prevalence from 22-100%. Although several ruminant species have been implicated in outbreaks of illness, the role of other food production animals in the spread of the disease is unclear. Included here are experimental studies conducted to determine the ability of chickens and pigs to become persistently infected with E. coli O157:H7 and the possibility of these animals becoming potential reservoirs. Broiler chickens and feeder pigs were inoculated with five E. coli strains. The inoculum included two Shigatoxigenic E. coli (STEC) O157:H7 strains, two enterotoxigenic E. coli (ETEC) strains and one enteropathogenic E. coli (EPEC) strain. A high dose inoculum with all five strains at approximately 1010 cfu/animal and a low dose inoculum with the STEC strains at approximately 107 cfu/animal and the EPEC and ETEC strains remaining at approximately 1010 cfu/animal were used. All of the strains persisted in the feces of some chickens given the high dose inoculum at two weeks post inoculation (pi). However, none of the strains persisted in the alimentary tracts of chickens at two months. In contrast to the results with chickens, the STEC strains persisted in the alimentary tracts of some pigs at two months pi following inoculation with both the high and low dose inocula. When all strains were given at approximately 1010 cfu (high dose inoculum) the STEC strains persisted in greater numbers and in more pigs than did the other strains. The results of this study demonstrated that persistent ([Greater than or equal to symbol]2 months) E. coli O157:H7 infections can occur in pigs. These findings were similar to those reported from sheep inoculated with the same set of E. coli strains.</p

Intimin Facilitates Colonization by Escherichia coli O157:H7 in Adult Ruminants

We compared the magnitude and duration of fecal shedding of wild-typeEscherichia coli O157:H7 to that of an isogenic intimin mutant in young adult cattle and sheep. In both ruminant species, wild-type E. coli O157:H7 was shed in greater numbers and for a longer duration than was the intimin mutant.This article is from Infection and Immunity 70 (2002): 2704, doi:10.1128/IAI.70.5.2704-2707.2002. Posted with permission.</p

Intimin Facilitates Colonization by Escherichia coli O157:H7 in Adult Ruminants

We compared the magnitude and duration of fecal shedding of wild-type Escherichia coli O157:H7 to that of an isogenic intimin mutant in young adult cattle and sheep. In both ruminant species, wild-type E. coli O157:H7 was shed in greater numbers and for a longer duration than was the intimin mutant

Colonization and Transmission of Escherichia Coli O157:H7 in Swine

Escherichia coli O157:H7 and other serogroups of Shiga toxin-producing E.coli (STEC) have emerged over the last several decades as a significant cause of food-borne illness in the United States. Approximately 5-10% of people clinically infected by these bacteria develop a systemic disease, hemolytic uremic syndrome, which has a fatality rate of approximately 5%. The Centers for Disease Control estimates that STEC cause some 110,000 illnesses and 90 deaths annually in the United States (Mead et al. 1999). In addition, the economic consequences of recalling large lots of food for public health reasons are significant. Cattle are considered to be the primary reservoir for STEC. Depending on the season, the methods used for bacterial culture and the age of the animals, the prevalence of E. coli O157:H7 in U.S. cattle ranges from 2-28% (Hancock et al. 1994; Elder et al. 2000). E.coli O157:H7 has also been recovered from other ruminants such as sheep (Kudva et al. 1996) and deer (Keene et al. 1997; Sargeant et al. 1999).This is a chapter from Perspectives on Food-Safety Issues of Animal-Derived Foods. 2010: 27-33. Posted with permission.</p

Prevalence of Virulence Factors Among Escherichia coli

Polymerase chain reaction (PCR) assays were used to characterize 575 Escherichia coli isolates from swine submitted to the veterinary diagnostic laboratory from January through May 1998. About one-third of the isolates carried genes characteristic of enterotoxigenic (ETEC), or Shiga toxin-producing (STEC), or attaching and effacing (AEEC) E. coli pathotypes. The ETEC were the most common pathotype. The data indicate that vaccination or vaccine development based on F18 and K88 pilus antigens continues to be appropriate for the control of ETEC infections. The STEC and AEEC infections also contribute to intestinal diseases in swine but apparently at lower prevalences than ETEC in this population. Nearly 25% of the ETEC lacked genes for any of the pilus types included in the assay. It is not known if these are nonpathogenic ETEC or if they produce other (as yet undiscovered) pilus antigens. If the latter interpretation is correct, they could represent an emerging population of ETEC pathogens not reflected in current pilus-based vaccines and diagnostic tests. There were also a number of strains that carried genes for K88 or F18 pili but did not have genes for enterotoxins. It was speculated that such strains may be acting as naturally occurring live oral pilus vaccines in herds where they occur.</p

Persistent Colonization of Sheep by Escherichia coli O157:H7 and Other E. coli Pathotypes

Shiga toxin-producing Escherichia coli (STEC) is an important cause of food-borne illness in humans. Ruminants appear to be more frequently colonized by STEC than are other animals, but the reason(s) for this is unknown. We compared the frequency, magnitude, duration, and transmissibility of colonization of sheep by E. coli O157:H7 to that by other pathotypes of E. coli. Young adult sheep were simultaneously inoculated with a cocktail consisting of two strains of E. coli O157:H7, two strains of enterotoxigenic E. coli (ETEC), and one strain of enteropathogenic E. coli. Both STEC strains and ETEC 2041 were given at either 10(7) or 10(10) CFU/strain/animal. The other strains were given only at 10(10) CFU/strain. We found no consistent differences among pathotypes in the frequency, magnitude, and transmissibility of colonization. However, the STEC strains tended to persist to 2 weeks and 2 months postinoculation more frequently than did the other pathotypes. The tendency for persistence of the STEC strains was apparent following an inoculation dose of either 10(7) or 10(10) CFU. One of the ETEC strains also persisted when inoculated at 10(10) CFU. However, in contrast to the STEC strains, it did not persist when inoculated at 10(7) CFU. These results support the hypothesis that STEC is better adapted to persist in the alimentary tracts of sheep than are other pathotypes of E. coli