Harley W. Moon

Plasmid-mediated adhesion in enteropathogenic Escherichia coli.

Summary: A survey of classical serotype enteropathogenic Escherichia coli has been made with respect to their plasmid profile and ability to adhere to HEp‐2 cells. Thirty‐one of the 32 strains examined contained a 50‐70 Md plasmid, and many exhibited HEp‐2 adherence. Strain E2348 (0127:H6), which causes diarrhea in volunteers and is HEp‐2‐adhesive, was chosen for further study. The large 55 Md plasmid in E2348, pMAR2, has been marked with a transposon coding for ampicillin resistance. E2348 that has been cured of pMAR2 loses the ability to adhere to HEp‐2 cells, while HB101, a nonadherent E. coli K12, acquires HEp‐2 adhesiveness after gaining this plasmid. Plasmid presence was also shown to correlate with in vivo adhesion to intestine, using the colostrum‐deprived piglet model.

Vaccination of pregnant dams with intimin(O157) protects suckling piglets from Escherichia coli O157:H7 infection.

ABSTRACT Cattle are important reservoirs of enterohemorrhagic Escherichia coli (EHEC) O157:H7 that cause disease in humans. Both dairy and beef cattle are asymptomatically and sporadically infected with EHEC. Our long-term goal is to develop an effective vaccine to prevent cattle from becoming infected and transmitting EHEC O157:H7 to humans. We used passive immunization of neonatal piglets (as a surrogate model) to determine if antibodies against EHEC O157 adhesin (intiminO157) inhibit EHEC colonization. Pregnant swine (dams) with serum anti-intimin titers of ≤100 were vaccinated twice with purified intiminO157 or sham-vaccinated with sterile buffer. IntiminO157-specific antibody titers in colostrum and serum of dams were increased after parenteral vaccination with intiminO157. Neonatal piglets were allowed to suckle vaccinated or sham-vaccinated dams for up to 8 h before they were inoculated with 106 CFU of a Shiga toxin-negative (for humane reasons) strain of EHEC O157:H7. Piglets were necropsied at 2 to 10 days after inoculation, and intestinal samples were collected for determination of bacteriological counts and histopathological analysis. Piglets that ingested colostrum containing intiminO157-specific antibodies from vaccinated dams, but not those nursing sham-vaccinated dams, were protected from EHEC O157:H7 colonization and intestinal damage. These results establish intiminO157 as a viable candidate for an EHEC O157:H7 antitransmission vaccine.

Intimin facilitates colonization by Escherichia coli O157:H7 in adult ruminants.

ABSTRACT 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.

Long Polar Fimbriae Contribute to Colonization by Escherichia coli O157:H7 In Vivo

ABSTRACT The contribution of long polar fimbriae to intestinal colonization by Escherichia coli O157:H7 was evaluated in sheep, conventional pigs, and gnotobiotic piglets. E. coli O157:H7 strains with lpfA1 and lpfA2 mutated were recovered in significantly lower numbers and caused fewer attachment and effacement lesions than the parent strain.

Persistent colonization of sheep by Escherichia coli O157: H7 and other E. coli pathotypes.

ABSTRACT 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 107 or 1010CFU/strain/animal. The other strains were given only at 1010 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 107 or 1010 CFU. One of the ETEC strains also persisted when inoculated at 1010 CFU. However, in contrast to the STEC strains, it did not persist when inoculated at 107 CFU. These results support the hypothesis that STEC is better adapted to persist in the alimentary tracts of sheep than are other pathotypes ofE. coli.

Pathogenesis of Escherichia coli O157:H7 in weaned calves.

Cattle are an important reservoir of Shiga toxin-producing Escherichia coli O157:H7 and other enterohemorrhagic E. coli (EHEC) that cause diarrhea, hemorrhagic colitis, and hemorrhagic uremic syndrome in humans. One strategy for reducing human foodborne EHEC infections is to reduce the levels of EHEC in cattle. Bovine O157:H7 infection models will facilitate identification of virulence factors involved in bovine infections. O157:H7 cause severe diarrhea and attaching and effacing (A/E) mucosal lesions in colostrum-deprived neonatal (< 2 h) calves. We hypothesized that O157:H7 also cause A/E lesions in older calves, but these were not detected in earlier studies because intestinal levels of O157:H7 were too low (< 10(6) CFU/g of tissue) for detection of focally distributed microscopic lesions. Weaned 3- to 4-month-old calves were fasted 48 h, inoculated via stomach tube with 10(10) CFU of O157:H7 or nonpathogenic E. coli, necropsied 4 d pi and examined histologically. Calves inoculated with O157:H7 had higher intestinal levels of inoculated E. coli than control animals. The rectum was the major site of colonization. A/E lesions were seen in the rectum and cecum of calves with high levels of O157:H7. Weaned calves, like neonatal calves, are susceptible to intestinal damage induced by EHEC O157:H7. The rectum and cecum may be principal sites of EHEC O157:H7 colonization during the carrier-shedder state in cattle.

Prevalences of Some Virulence Genes among Escherichia Coli Isolates from Swine Presented to a Diagnostic Laboratory in Iowa

1. Anver MR, Park JS, Rush HG: 1976, Dermatophilus in the marble lizard (Calotes mystaceus). Lab Anim Sci 26:817–823. 2. Biberstein EL: 1990, The skin as a microbial habitat: bacterial skin infections. In: Review of veterinary microbiology, ed. Biberstein EL, Zee YC, pp. 268–270. Blackwell, Cambridge, MA. 3. Chineme CN, Addo PB: 1980, Pathologic changes in lizards (Agama agama) experimentally infected with Dermatophilus congolensis. J Wild Dis 16:407–412. 4. Gordon MA: 1964, The genus Dermatophilus. J Bacteriol 88: 509–522. 5. Jacobson ER: 1989, Dermatophilosis in reptiles. Int Colloq Pathol Reptiles Amphib 3:47. [Abstr.] 6. Jacobson ER: 1991, Diseases of the integumentary system of reptiles. In: Dermatology for the small animal practitioner, exotics, feline, canine, ed. Nesbitt GH, Ackerman LJ, pp. 225– 239. Veterinary Learning Systems, Trenton, NJ. 7. Jones RT: 1976, Subcutaneous infection with Dermatophilus congolensis in a cat. J Comp Pathol 86:415–421. 8. LaScola B, Raoult D: 1998. Molecular identification of Gemella species from three patients with endocarditis. J Clin Microbiol 36:866–871. 9. Lloyd DH: 1984, Immunology of Dermatophilus: recent developments and prospects for control. Prev Vet Med 2:93–102. 10. Masters AM, Ellis TM, Carson JM, et al.: 1995, Dermatophilus chelonae sp. nov., isolated from chelonids in Australia. Int J Syst Bacteriol 45:50–56. 11. Montali RJ, Smith EE, Davenport M, et al.: 1975, Dermatophilosis in Australian bearded lizards. J Am Vet Med Assoc 167: 553–555. 12. Roberts DS: 1961, The life cycle of Dermatophilus dermatonomus, the causal agent of ovine mycotic dermatitis. Aust J Exp Biol Med Sci 39:463–476. 13. Simmons GC, Sullivan ND, Green PE: 1972, Dermatophilus in a lizard (Amphibolurus barbatus). Aust Vet J 48:465–466.

Escherichia coli O157:H7 Causes More-Severe Systemic Disease in Suckling Piglets than in Colostrum-Deprived Neonatal Piglets

ABSTRACT Our objective was to determine if suckling neonatal piglets are susceptible to enterohemorrhagic Escherichia coli (EHEC) O157:H7 disease. Surprisingly, EHEC O157:H7 caused more-rapid and more-severe neurological disease in suckling neonates than in those fed an artificial diet. Shiga toxin-negative O157:H7 did not cause neurological disease but colonized and caused attaching-and-effacing intestinal lesions.

Pathogenesis of O157:H7 Escherichia Coli Infection in Neonatal Calves

Cattle have been implicated as an important reservoir of Shiga-like toxin-producing Escherichia coli (SLTEC) O157:H7, enterohemorrhagic E. coli (EHEC) that cause hemorrhagic colitis and hemorrhagic uremic syndrome in humans. Naturally- or experimentally-infected cattle can shed low levels of E. coli O157:H7 long-term, but little is known about the pathogenesis of E. coli O157:H7 infection in cattle. E. coli O157:H7 induce characteristic attaching and effacing (A/E) mucosal lesions in ceca and colons of 1-day-old gnotobiotic piglets and this model is used to study the pathogenesis of SLTEC infections. A/E lesions were not detected in histologic sections of the intestines from adult cattle or 3- to 14-week-old calves infected with E. coli O157:H7. Our objective was to determine if E. coli O157:H7 induce A/E lesions in neonatal calves. Colostrum-deprived calves (< 12-h-old) were bottle-fed with antibiotic-free milk replacer containing 10(10) colony forming units (CFU) of O157:H7 (SLT-I+, SLT-II+) or nonpathogenic E. coli, necropsied 18 h postinfection and their intestines examined histologically. Bacterial attachment, effacement of microvillous borders, and destruction of epithelium were observed in the intestines of the neonatal calves inoculated with E. coli O157:H7. No lesions were observed in calves inoculated with nonpathogenic E. coli. The distribution of intestinal lesions in neonatal calves resembled that in gnotobiotic pigs. Neonatal calves are apparently more susceptible to A/E lesions induced by E. coli O157:H7 than are older calves or adult cattle and provide a model for studying the pathogenesis of E. coli O157:H7 infections in cattle.

Shiga Toxin-Producing Escherichia coli Infection: Temporal and Quantitative Relationships among Colonization, Toxin Production, and Systemic Disease

Edema disease, a naturally occurring disease of swine caused by Shiga toxin-producing Escherichia coli (STEC), was used as a model for the sequence of events that occur in the pathogenesis of STEC infection. The mean time from production of levels of Shiga toxin 2e (Stx2e) detectable in the feces (day 1) to the onset of clinical disease (neurologic disturbances or death) was 5 days (range, 3-9). Bacterial colonization and titers of Stx2e in the ileum peaked at 4 days after inoculation in pigs without signs of clinical disease and at 6 days after inoculation in clinically affected pigs. Animals with the greatest risk of progressing to clinical disease tended to have the highest fecal toxin titers (>/=1:4096). Stx2e was detected in the red cell fraction from blood of some pigs showing clinical signs of edema disease but was not detected in the serum or cerebrospinal fluid.