AUTHOR=Becker Christin , Adam Aysegül , Dommisch Henrik , Stach Thomas , Schaefer Arne S. 

TITLE=In vitro induction of Entamoeba gingivalis cyst-like structures from trophozoites in response to antibiotic treatment

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=13

YEAR=2023

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2023.1201394

DOI=10.3389/fcimb.2023.1201394

ISSN=2235-2988

ABSTRACT=<sec><title>Background</title><p>Entamoeba <italic>gingivalis (E. gingivalis)</italic> is an anaerobic protozoan that is strongly associated with inflamed periodontal pockets. It is able to invade the mucosal epithelium of the human host, where it can feed on epithelial cells and elicit a severe innate immune response. Unlike other <italic>Entamoeba</italic> species, it is considered that <italic>E. gingivalis</italic> cannot form cysts, because it is a non-infectious protozoan. The lack of encystation capability would make it susceptible to periodontal treatment. However, it is not clear how the human host becomes infected with <italic>E. gingivalis</italic> trophozoites. We investigated the ability of <italic>E. gingivalis</italic> to encapsulate in response to an unfavorable environment <italic>in vitro</italic>.</p></sec><sec><title>Methods</title><p>Different strains of <italic>E. gingivalis</italic>, isolated from inflamed periodontal pocket samples, were cultured for 8 days in the presence or absence of the antimicrobials amoxycillin and metronidazole. To reveal cyst formation, we investigated the morphology and ultrastructure of the amoeba by light, fluorescence, transmission and scanning electron microscopy. We also used the fluorescent dye calcofluor white M2R to demonstrate chitin present in the cyst wall.</p></sec><sec><title>Results</title><p>We observed exocysts and an intra-cystic space separating the encapsulated trophozoite from the environment. Remarkably, cysts showed a smooth surface, polygonal edges and smaller size compared to free-living trophozoites. In addition, encapsulated trophozoites that detached from the cyst wall had a dense cytoplasma without phagocytic vesicles. The cyst walls consisted of chitin as in other <italic>Entamoba</italic> species. The encapsulated trophozoids were mononuclear after antibioticinduced encapsulation.</p></sec><sec><title>Discussion</title><p>We conclude that <italic>E. gingivalis</italic> cyst formation has significant implications for dissemination and infection and may explain why established treatment approaches often fail to halt periodontal tissue destruction during periodontitis and peri-implantitis.</p></sec>