Transmission ofHelicobacterspp. A challenge to the dogma of faecal-oral spread

Abstract

SUMMARY: Faecal oral spread is claimed by many to be the mode of transmission of the gastric pathogenHelicobacter pylori. This idea is based not on experimental data but because the epidemiology ofH. pyloriinfection resembles that of other pathogens known to be spread by the faecal-oral route. This is in spite of the observation that no-one has been successful in culturingH. pylorifrom human stool. In this study, a series of transmission experiments are reported on animals infected with the gastric spirilla,Helicobacter felisand ‘Gastrospirillum hominis’. Germfree mice and rats infected withH. felisdid not transmit their infection to uninoculated mice despite prolonged contact in the same cage nor could the bacterium be isolated from their intestinal contents. This was confirmed in specific pathogen free mice where infected dams did not pass the helicobacter to their progeny. Similarly, mice infected with a human isolate of ‘Gastrospirillum hominis’ did not transmit the infection while in close contact with uninoculated mice. In contrast, in a limited series of experiments, bothH. pyloriandH. feliswere transmitted from infected gnotobiotic Beagle puppies to uninfected animals in the same enclosure. In addition, the gastric mucus from a cat with indigenous ‘Gastrospirillum’-like organisms was infectious for mice, whereas faecal content from the same animal was not. It is suggested that the difference between the murine and canine experiments is that the dogs are more likely to have oral-oral contact than rodents. Unlike dogs, mice and rats do not vomit and are coprophagous. It is concluded that the case for faecal-oral spread ofHelicobacterspecies is ‘not proven’ and that the inter-oral route is more likely.