Biology of Campylobacter fetus S-Layer Proteins

Abstract

Campylobacter fetus (formerly called Vibrio fetus) is a microaerophilic, curved, motile, gram-negative bacterium. Originally described early in this century as causes of bovine infertility, these organisms now are known to be pathogenic for both animals and humans (Smibert, 1984). Two major subspecies are recognized that are closely related; C. fetus subsp. fetus and C. fetus subsp. venerealis. C. fetus subsp. fetus has a broad host range including sheep, cattle, horses, poultry, and reptiles; humans are occasionally infected. In sheep and cattle, following oral ingestion, there is bacteremia. Pregnant ewes and cows may abort because of the tropism of the organism for the placenta. In other infected ungulates, infection may be inapparent but eventually may lead to chronic biliary carriage and fecal excretion. Humans occasionally ingest C. fetus in foods, but illness mostly occurs in compromised hosts. Bacteremia is the hallmark of clinically significant human infections, which may then result in lesions in organs distant to the gastrointestinal tract (Blaser and Relier, 1981). C. fetus infection of humans may be underdiagnosed because of the fastidious nature of these organisms (Wang and Blaser, 1986). C. fetus subsp. venerealis infection is essentially confined to cattle. Bulls carry the organism in the penile prepuce and overlaying the deep epithelial crypts, and introduce it into cows via sexual intercourse. Infection causes endometritis, which leads to infertility. After several months, cows are usually able to clear this infection focus but chronic vaginal colonization may persist for months or years.