Avian Chlamydiosis

Recent findings in research on avian chlamydiosis include an increase in the reported prevalence of Chlamydia (C.) psittaci in poultry flocks, detailed descriptions of molecular processes governing the course of infection in vivo, as well as the discovery of new chlamydial species. Here we review the major advances of the last 6 years. In particular, we suggest that the observed re-emergence of C. psittaci infections in domestic poultry are due to a reduction in the use of antibiotics and better diagnostic assays. Cellular and animal models have significantly contributed to improving our understanding of the pathogenesis, including the events leading to systemic disease. The elucidation of host-pathogen interactions revealed the efficiency of C. psittaci in proliferating and disseminating despite the action of pro-inflammatory mediators and other factors during host immune response. Finally, the recent introduction of C. avium and C. gallinacea sheds new light on the epidemiology and aetiopathology of avian chlamydiosis

One face of Chlamydia trachomatis: the infectious elementary body

The lifestyle of Chlamydiae is unique: the bacteria alternate between two morphologically distinct forms, an infectious non-replicative elementary body (EB), and a replicative, non-infectious reticulate body (RB). This review focuses on recent advances in understanding the structure and function of the infectious form of the best-studied member of the phylum, the human pathogen Chlamydia trachomatis. Once considered as an inert particle of little functional capacity, the EB is now perceived as a sophisticated entity that encounters at least three different environments during each infectious cycle. We review current knowledge on its composition and morphology, and emerging metabolic activities. These features confer resistance to the extracellular environment, the ability to penetrate a host cell and ultimately enable the EB to establish a niche enabling bacterial survival and growth. The bacterial and host molecules involved in these processes are beginning to emerge

Deconstructing the Chlamydial Cell Wall

The evolutionary separated Gram-negative Chlamydiales show a biphasic life cycle and replicate exclusively within eukaryotic host cells. Members of the genus Chlamydia are responsible for many acute and chronic diseases in humans, and Chlamydia-related bacteria are emerging pathogens. We revisit past efforts to detect cell wall material in Chlamydia and Chlamydia-related bacteria in the context of recent breakthroughs in elucidating the underlying cellular and molecular mechanisms of the chlamydial cell wall biosynthesis. In this review, we also discuss the role of cell wall biosynthesis in chlamydial FtsZ-independent cell division and immune modulation. In the past, penicillin susceptibility of an invisible wall was referred to as the "chlamydial anomaly." In light of new mechanistic insights, chlamydiae may now emerge as model systems to understand how a minimal and modified cell wall biosynthetic machine supports bacterial cell division and how cell wall-targeting beta-lactam antibiotics can also act bacteriostatically rather than bactericidal. On the heels of these discussions, we also delve into the effects of other cell wall antibiotics in individual chlamydial lineages