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

Abstract

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.

Peptidoglycan in obligate intracellular bacteria

“…The two major human pathogens are C. trachomatis and C. pneumoniae. However, some of the lesser-known socalled 'environmental' chlamydia (sometimes referred to as 'chlamydia-like' bacteria), which live inside amoeba, have recently been described as putative human pathogens, including Waddlia chondrophila and possibly Simkania negevensis (Ammerdorffer et al, 2017;Vouga et al, 2017). Chlamydiae are tropic for endothelial, epithelial and monocyte/macrophage cells and even primitive macrophage-like cells such as amoebae (Kebbi-Beghdadi and Greub, 2014).…”

Simkania negevensis, an Example of the Diversity of the Antimicrobial Susceptibility Pattern among Chlamydiales

“…A 6- or 7-day-old coculture, diluted 1:1,000, was used to inoculate fresh A549 cells or Vero cells that had been seeded previously at 1.5 × 10 5 cells/ml on a 24-well plate (Corning), as described previously (7). At 2 h postinfection, the medium was changed for medium containing 2-fold serial dilutions of various antibiotics.…”

“…negevensis particles treated with β-lactams, fosfomycin, and vancomycin, in immunofluorescence assays using an in-house rabbit polyclonal anti-S. negevensis antibody, as described previously (7). As shown in Fig.…”

“… Simkania negevensis strain Z was grown at 37°C in Vero cells in 25-cm 2 cell culture flasks (Corning, USA), in Dulbecco's modified essential medium (DMEM) (PAN Biotech, Aidenbach, Germany) supplemented with 10% fetal calf serum (FCS), with 5% CO 2 . A 6- or 7-day-old coculture, diluted 1:1,000, was used to inoculate fresh A549 cells or Vero cells that had been seeded previously at 1.5 × 10 5 cells/ml on a 24-well plate (Corning), as described previously ( 7 ). At 2 h postinfection, the medium was changed for medium containing 2-fold serial dilutions of various antibiotics.…”

“…Growth at day 2 was also assessed for β-lactams, fosfomycin, and vancomycin, to ensure the absence of effects due to instability of the compounds after 48 h at 37°C. An in-house specific quantitative PCR targeting the 16S rRNA gene was used to quantify S. negevensis DNA, as described previously ( 7 ). The absence of antibiotic toxicity toward cells was determined by examining the microplates using an inverted microscope (Zeiss Axiovert 25; Carl Zeiss).…”