Necrotoxigenic Escherichia coli type-2 invade and cause diarrhoea during experimental infection in colostrum-restricted newborn calves

Abstract

There exists experimental evidence that necrotoxigenic Escherichia coli (NTEC) strains producing the cytotoxic necrotising factor 1 cause intestinal and extra-intestinal disease in piglets. On the other hand, no experimental model has been developed with NTEC strains producing the cytotoxic necrotising factor 2. In all, 14 colostrum-restricted calves were orally challenged with two strains isolated from the faeces of a diarrheic calf (B20a) or from the heart blood of a septicaemic calf (1404). All calves had diarrhoea which lasted until euthanasia in eight of them. In those calves, diarrhoea was correlated with the faecal excretion of the challenge strains. At necropsy, vascular congestion of the intestinal mucosa, hypertrophy of the mesenteric lymph nodes (MLN) and some congestion of the lungs were observed. Bacteriology confirmed the colonisation of the intestine by the challenge strains which were also recovered from the heart blood, the lungs and/or the liver. Histological sections confirmed enterocolitis, lymphadenitis and limited bronchopneumonia. In the intestinal tissue sections, bacteria testing positive in an in situ DNA hybridisation assay with a CNF2 probe were observed. Those results were confirmed by immunohistochemistry with a polyclonal anti-O78 and a monoclonal anti-F17b antisera. Three of the five control calves receiving either saline or a CNF À , F17a strain (25KH09) had no clinical signs or lesions. The other two presented a profuse liquid diarrhoea but those calves were positive for the presence of K99 þ E. coli. In this model, both NTEC2 strains were thus, able to colonise the intestine, to cause long-lasting diarrhoea and to invade the blood stream with localisation in various internal organs in colostrumrestricted conventional newborn calves. #

Molecular characteristics of Escherichia coli serogroup O78 strains isolated from diarrheal cases in bovines urge further investigations on their zoonotic potential

“…They are also widely distributed in healthy cattle and calves [37 -40]. Experimental infections of calves with NTEC-2 have shown that these bacteria are able to colonize the intestine and enter the bloodstream, but their potential to cause clinical symptoms strongly depends on the hosts immune status, and NTEC-2 thus are supposed to be opportunistic pathogens [5]. We were not able to identify genes coding for both ColV-and Vir-plasmid-determinants which is in accordance with other studies on bovine O78 strains [9,41].…”

“…Recently, also necrotoxigenic E. coli (NTEC) gained more attention in diarrheagenic infections in cattle [5,6]. In humans, however, during the last decade, other E. coli pathotypes associated with diarrhea have been increasingly identified, namely enteroinvasive (EIEC), diffuse adhering (DAEC), enteroaggregative (EAEC), and certain necrotoxigenic (NTEC) E. coli.…”

Detection of cytotoxic necrotizing factor types 1 and 2 among fecal Escherichia coli isolates from brazilian children with and without diarrhea

“…The role of CNF-producing E. coli strains in diarrheal diseases has not been defined. Recently, Van Bost et al (2001b) reported that CNF2-producing strains were able to colonize the intestines, cause long-lasting diarrhea, and invade the blood stream of newborn colostrum-restricted calves after experimental inoculation through the oral route. A previous report on the experimental infection of germfree colostrum-deprived newborn piglets showed no evidence for a pathogenic role of CNF1 in the development of diarrhea (Fournout et al 2000).…”

Isolation from a sheep of an attaching and effacing Escherichia coli O115:H− with a novel combination of virulence factors

“…CNF2-producing strains have been isolated from calves and lambs with diarrhoea or bacteraemia, or both [40]. Experimental inoculation of an E. coli strain with proven CNF2 toxin expression into colostrum-restricted newborn calves resulted in intestinal colonisation, causing long-lasting diarrhoea and bacteraemia with localisation in various internal organs [41].…”