Background Gardnerella vaginalis is one of the commonest organisms that causes bacterial vaginosis, which is also implicated as a risk factor of preterm birth. This bacterium is also considered the second commonest cause of intrauterine inflammation (chorioamnionitis). Although it creates the characteristic “clue cells” when infecting the vaginal epithelium, the evidence of its pathogenicity on other epithelial surfaces is lacking.
Aim To study the pathogenic changes on the human respiratory tract epithelium as the basis for the understanding of Gardnerella vaginalis-induced fetal lung inflammation, which may occur in preterm intrauterine infection.
Methods A549®ATCC Human alveolar basal epithelial cell line was grown over an average period of 48–72 h before exposure to Gardnerella vaginalis serotype ATCC® 14018TM. The multiplicity of infection (MOI) of 100 was used to infect the cell line over a period of 4h. Adherence, apoptosis and cytotoxicity changes were studied using immunofluorescence and light microscopy. Comparisons were also made to E.coli and GBS, the common pathogens causing neonatal sepsis.
Results Gardnerella vaginalis showed similar adherence to E.coli. It has moderate cytotoxicity when compared to GBS. At 4h, co-culturing Gardnerella vaginalis with A549 cell line consistently exhibited the presence of apoptosis in more than 50% of the cells as shown using the TUNEL assay. Cytotoxicity was confirmed morphologically with cellular features of pyknosis and elevated LDH in culture supernatant.
Conclusions Gardnerella vaginalis exerts some characteristic changes of infection on respiratory epithelium with signs of cytotoxicity, suggesting that the fetal lung could be similarly affected when this bacterium causes intrauterine infection.