[Experimental study on the pathogenesis of Entamoeba gingivalis].

OBJECTIVE: To study the pathogenesis of Entamoeba gingivalis (E. g.) and its relation to periodontal diseases. METHODS: Rats were treated with immuno-inhibitor for one week and the neck of incisor teeth of the rats was bound with steel wire. They were randomly divided into three groups: the first group was infected by E. g. in the periodontal tissue, the second group was infected by symbiotic bacteria (s. b.), and the third group was given physiological saline as control. Observation on the periodontal inflammation was made for each group of rats, and the purulent secretion from periodontal abscess was examined for living pathogens. RESULTS: The incidence of periodontal diseases in rats infected by E. g. was higher than that of symbiotic bacteria group and that of control (P < 0.05), the incidence of periodontal diseases in rats infected by s. b. was higher than that of control group (P < 0.05). Living pathogens were found in the abscess liquid. CONCLUSION: E. g. is an opportunistic pathogen, which, together with synergistic symbiotic bacteria, can cause periodontal diseases in hosts with low immunity.

[Studies on the continuous culture and pathogenicity of Entamoeba gingivalis].

OBJECTIVE: To establish a method for continuous culture of Entamoeba gingivalis (E. g.) and study the pathogenicity of E. g.. METHODS: The culture conditions of E. g. were compared by observing its growth and reproduction. The pathogenicity of E. g. was studied by investigating its infection rate in humans and observing the relationship between E. g. infection and periodontal abscess in rats and the in vitro effect of some drugs. RESULTS: The optimal culture condition of E. g. was modified LES medium containing Locke's solution with 20% bovine serum, penicillin, streptomycin and rice starch. Reproduction of E. g. peaked at the fourth day of incubatoin, E. g. could live continuously for 120 to 168 h. The infection rate of E. g. was higher in patients with periondontal diseases than in healthy groups. The animal test showed that E. g. could cause periondontal abscess in rats. The levels of acid phosphatase and MDA were higher in patients with E. g.-positive periondontal disease than in healthy individuals. Metronidazole and SBF are effective against E. g.. CONCLUSION: E. g. could grow very well in modified LES medium, and cause periondontal abscess in patients with low immunity.