Faculty of Veterinary Medicine University of Zagreb
Abstract
Day-old infant rabbits inoculated with enterohaemorrhagic Escherichia coli (EHEC) O157:H7 strain developed severe diarrhoea and ruffl ed coats, usually culminating in death. All rabbits (n=8) inoculated intragastrically with either UMDL 29 or MC 110 developed severe diarrhoea two days post inoculation. None of the control rabbits inoculated with PBS developed diarrhoea. The UMDL 29 and MC 110 infected rabbits also developed ruffl ed coats by day two post inoculation. Mortality started to occur on day four post infection. The diarrhoea which started 24 hr post inoculation was associated with loss of mass and infl ammation of the intestines. At necropsy, the ceca and colons of rabbits inoculated with either UMDL 29 or MC 110 were distended or fi lled with loose stool and fl uids. In contrast, the ceca and colons of rabbits inoculated with PBS were not distended and contained hard, formed pellets. The intestinal contents of the infected rabbits that died and of those that were euthanatized were fi lled with watery content. A microscopic examination of colons showed mild infl ammatory cell infi ltration, thinning of the intestinal wall, or necrotic foci. The lungs of infected rabbits were congested. The limitations of current animal models led us to reexamine the day-old infant rabbit model for the study of EHEC pathogenicity. This study indicates that infant rabbits are a useful model for investigation of the intestinal stage of EHEC pathogenesis and suggest that shiga toxin and other virulence factors of E. coli O157 may play a critical role in causing diarrhea and infl ammation in patients infected with EHEC.Pokusna zaraza enterohemoragičnim sojem bakterije Escherichia coli (EHEC) O157:H7 u jednodnevnih se kunića očitovala teškim proljevom, kovrčavom dlakom i uginućem. Teški proljev u kunića (n=8) zaraženih u želudac sojem označenim UMDL 29 ili sojem MC 110 razvio se dva dana nakon inokulacije. Proljev se nije javio u kontrolnih kunića inokuliranih puferiranom fi ziološkom otopinom. Kovrčavost dlačnog pokrivača javila se također dva dana nakon infekcije. Uginuća su se počela javljati četiri dana nakon infekcije. Proljev koji je
započeo 24 sata nakon inokulacije javio se kao posljedica upale crijeva, a doveo je do gubitka tjelesne mase. Razudbom je ustanovljeno da su slijepa crijeva u inokuliranih kunića bila naduta ili ispunjena rijetkim sadržajem odnosno tekućinom. Suprotno, slijepa crijeva i debelo crijevo kunića koji su dobili puferiranu fi ziološku otopinu nisu bila naduta, a sadržavala su tvrdo formirani feces. Crijevni sadržaj uginulih kao i eutanaziranih kunića bio je vodenast. Mikroskopska pretraga tkiva kolona pokazala je blagu infi ltraciju upalnih stanica, stanjenu stijenku crijeva i nekrotična žarišta. Ustanovljena je kongestija pluća u zaraženih kunića. Ograničene mogućnosti rabljenja dosadašnjih životinjskih modela potaknule su na ponovnu uporabu jednodnevnih kunića kao modela za istraživanje patogenosti EHEC. Može se zaključiti da se jednodnevni kunići mogu rabiti za proučavanje patogeneze crijevne infekcije uzrokovane EHEC te da šiga toksin i drugi čimbenici virulencije bakterije E. coli
O157 imaju kritičnu ulogu u nastanku proljeva i upale u pacijenata infi ciranih EHEC
