THE ISOLATION AND TRANSMISSION OF Helicobacter hepaticus sp. nov., ISOLATED FROM THE LIVERS AND INTESTINAL CONTENTS OF MICE

Abstract

In the fall of 1992 at the National Cancer Institute - Frederick Cancer Research and Development Center (NCI-FCRDC), A/JCr stock mice which showed suppurative skin lesions and treated and untreated A/JCr mice from a long-term toxicologic study were found to have a unique chronic active hepatitis of unknown etiology. No biological agent was known to cause such lesions. A major effort was undertaken to determine the cause of the hepatitis, since all these mice were obtained from the NCI-FCRDC Animal Production Area (NCI-FCRDC-APA). The initial approach was to examine potential environmental toxins. Upon failure to identify any specific environmental cause, a search for a possible biological agent was pursued. In the course of utilizing a Steiner's modification of the Warthin-Starry stain (Steiner's stain), pathologists found what appeared to be a helical organism in the hepatic parenchyma of affected mice. The hepatitis was successfully reproduced in A/J mice obtained from Jackson Laboratories (Jax), Bar Harbor, ME, which had been injected with liver suspensions from affected A/JCr mice. A histopathologic survey employing the Steiner's stain on livers from adult NCI-FCRDC-APA mice demonstrated hepatic lesions in numerous mouse strains (A/JCr, C3H/HeNCr, SJL/NCr, BALB/cAnNCr and SCID/NCr), while hepatic lesions were absent in others (C57BL/6NCr, B6C3F1 and nude [nu/nu]). Hepatic lesions were found more frequently in male mice than female mice. Isolation of the organism was accomplished by culturing the livers of affected A/JCr and SCID/NCr mice and incubating the suspensions on trypticase soy agar plates with 5% sheep blood and brucella blood agar with antibiotics at 37°C under microaerophilic conditions. The organism was motile, catalase positive, oxidase positive and rapidly hydrolyzed urea. The organism was tentatively designated Helicobacter hepaticus sp. nov. Subsequently, Helicobacter hepaticus sp. nov. has been cultured from the intestinal tract and feces of affected mice from the NCI-FCRDC-APA and research holding colonies. To demonstrate infectivity, the organism was injected into unaffected A/J mice from Jax. At several time points livers were aseptically collected, cultured, and a portion submitted for histopathological examination. The hepatitis and presence of the organism was confirmed by histopathology and culture. In a third transmission study, CB.17 SCID mice from Taconic Farms (Tac), Germantown, N.Y., were exposed by direct animal or fecal contact to affected SCID/NCr mice from NCI-FCRDC-APA. Over time the organism and the hepatitis were found to have been transmitted to the CB.17 SCID mice, thus demonstrating that the route of infection was fecal-oral. To date, there are no other organisms known to cause the same type of hepatitis as Helicobacter hepaticus sp. nov.. This novel organism has the potential to provide a much needed animal model for biocarcinogenesis and other human health problems.