Simkania negevensis may produce long-lasting infections in human pneumocytes and endometrial cells

Simkania negevensis is a novel Chlamydia-related bacterium and the founding member of the Simkaniaceae family within the Chlamydiales order. Little is known about the biology and pathogenesis of this bacterium. So far, S. negevensis has been considered as an amoebal symbiont, but its natural host remains unknown. Moreover, evidence of human exposition has been reported worldwide and an association with pneumonia and bronchiolitis is suspected. Here, we evaluated the ability of S. negevensis to replicate in potential environmental reservoirs, namely amoebae and arthropods, as well as in mammalian cells (Vero cells, pneumocytes and endometrial cells) and further evaluated the characteristics of its replicative vacuole. We demonstrated that S. negevensis efficiently replicates in all cell lines tested, with the shortest doubling time and an increased adhesion observed in pneumocytes. Our work highlights the specificities of the Simkania-containing vacuole compared to other Chlamydiales; contrarily to Chlamydia trachomatis, S. negevensis does not disrupt the Golgi apparatus. Importantly, our work suggests that S. negevensis infection is associated with few cytopathic effects and might persist for a prolonged time in infected cells. Further evaluation of its implication in human diseases is required; an implication in chronic or subacute respiratory infections might be suspected.