So close and yet so far – Molecular Microbiology ofCampylobacter fetus subspecies

摘要

Campylobacter fetus comprises two subspecies, C. fetus subsp. fetus and C. fetus subsp. venerealis, which are considered emerging pathogens in humans and animals. Comparisons at the genome level have revealed modest subspecies-specific variation; nevertheless, these two subspecies show distinct host and niche preferences. C. fetus subsp. fetus is a commensal and pathogen of domesticated animals that can be transmitted to humans via contaminated food. The clinical features of human infection can be severe, especially in impaired hosts. In contrast, C. fetus subsp. venerealis is a sexually transmitted pathogen essentially restricted to cattle. Infections leading to bovine venereal campylobacteriosis cause substantial economic losses due to abortion and infertility. Recent genome sequencing of the two subspecies has advanced our understanding of C. fetus adaptations through comparative genomics and the identification of subspecies-specific gene regions predicted to be involved in pathogenesis. The most striking difference between the subspecies is the highly subspecies-specific association of a pathogenicityisland in the C. fetus subsp. venerealischromosome. The inserted region encodes a Type 4 secretion system, whichcontributes to virulence properties of this organism in vitro.This review describes the main differences in epidemiological, phenotypic, andmolecular characteristics of the two subspecies and summarizes recent advancestowards understanding the molecular mechanisms of C. fetuspathogenesis.