Trichomonas vaginalis Weakens Human Amniochorion in an In Vitro Model of Premature Membrane Rupture

OBJECTIVE Trichomonas vaginalis (TV) infection is associated with preterm rupture of membranes (PROM) and preterm birth. We evaluated the effects of TV growth and metabolism on preparations of human amniochorion to understand and characterize how TV may impair fetal-membrane integrity and predispose to PROM and preterm birth. METHODS Term fetal membranes were evaluated using an established in vitro fetal-membrane model. Fresh TV clinical isolates were obtained from pregnant women. The protozoa (5.0x10(5) to 1.5x10(6)/ml) were incubated with fetal membranes in modified Diamond's medium for 20 h at 37 degrees C in 5% CO2.The effects of fetal-membrane strength (bursting tension, work to rupture, and elasticity) were measured using a calibrated Wheatstone-bridge dynamometer. Tests were also performed to evaluate the effects of 1) inoculum size; 2) metronidazole (50 microg/ml); and 3) cell-free filtrate. RESULTS The TV-induced membrane effects were 1) isolate variable; 2) inoculum dependent; 3) incompletely protected by metronidazole; and 4) mediated by both live organisms as well as protozoan-free culture filtrates. Six of 9 isolates significantly reduced the calculated work to rupture (P < or = 0.02); 7 of 9 reduced bursting tension; and 1 of 9 reduced elasticity. One isolate significantly increased the work to rupture and bursting tension (P < or = 0.002). CONCLUSIONS In vitro incubation of fetal membranes with TV can significantly impair the measures of fetal-membrane strength. This model may be used to delineate the mechanisms of TV-induced membrane damage. This study suggests that there are enzyme-specific effects as well as pH effects.