M. VOUGA¹, D. BAUD², G. GREUB<sup>1

1</sup>Center for Research on Intracellular Bacteria, Institute of Microbiology, Faculty of Biology and Medicine, University of Lausanne and University Hospital, Lausanne, Switzerland, ²Materno-fetal and Obstetrics Research Unit, Department “Femme-Mère-enfant”, Maternity, University Hospital, Lausanne, Switzerland

Simkania negevensis (Sneg) is an emerging Chlamydia-related bacterium. As other Chlamydiales, it is an obligate intracellular bacterium characterized by a biphasic developmental cycle. A growing interest has developed towards Chlamydia-related bacteria as they provide new insights in the biology of the Chlamydiales and may represent potential emerging pathogens. Indeed, W. chondrophila and P. acanthamoebae have been associated with miscarriages and lower respiratory tract diseases, respectively.
Little is known about the biology and pathogenesis of Sneg. Evidence of human exposition has been reported worldwide and current data suggest an association with pneumonia and bronchiolitis. In addition, its similarities with adverse pregnancy outcomes-related pathogens (C. trachomatis or W. chondrophila) make it a putative candidate for genital infections and obstetrical complications.
Here, we characterized the growth cycle of Sneg in Vero cells, endometrial cells (Ishikawa cell line) and pneumocytes (A549 cell line) using a specific quantitative PCR, specifically developed, immunofluorescence and a mortality assay, based on propidium iodide incorporation.
Sneg efficiently replicated in these cell lines within 6 days and new infective particles were released in the cell culture supernatant starting from day 3. Infectivity was higher in pneumocytes. No cytopathic effects were observed as shown by similar mortality rates in both infected and uninfected cells. We confirmed that Sneg-containing vacuole is closely associated with the endoplasmic reticulum and mitochondria in these cell lines and showed that Sneg does not induce Golgi apparatus fragmentation. These findings emphasize the specificities of the replication cycle and host nutrients parasitism in each family level lineage of Chlamydiales members. From a clinical perspective, our work suggests that Sneg infection might persist for a prolonged time in pneumocytes or endometrial cells and induce chronic lung or endometrial infections. These data strongly support the role of Sneg as an agent of lower respiratory tract infections and should encourage clinicians to assess its implication in genital tract infections.