[Pathogenicity of Ureaplasma urealyticum serotype 3 in genital tract of mice].

OBJECTIVE: To study the pathogenicity of Ureaplasma urealyticum serotype 3 (UU3) with different concentration in the genital tract of the mice. METHODS: A total of 156 Kunming mice were divided into 4 groups randomly, including group A, B, C (48 mice in every experimental group) and control group (12 mice in control group). UU 3 at concentration of 1x10(7) copy/g (group A), 1x10(6) copy/g (group B), 1x10(5) copy/g (group C) were inoculated into 48 mice in every experimental group intravaginally, in the mean time, culture medium of UU was given into 12 mice in control group. They were necropsied at 1, 3, 7, 14, 21, 35 days of postinoculation randomly, which included 8 mice of every experimental group and 2 mice of control group every time, and to detect UU3 expression from cervical secretions by FQ-PCR and observing the pathogenicity rate in tissues of cervix, endometrium, fallopian tube by light microscope and calculate the morbidity rate. RESULTS: (1) The total positive rates of UU3 were 63% (30/48) in group A, 50% (24/48) in group B, 17% (8/48) in group C, which showed a significant difference (P<0.01). And at 1, 3, 7, 14, 21, 35 days of postinoculation, the positive rates of group A were 8/8, 7/8, 6/8, 5/8, 4/8 and 0, group B were 7/8, 5/8, 5/8, 4/8, 3/8 and 0, group C were 3/8, 2/8, 2/8, 1/8, 0 and 0; all mice in control group were zero. At all time points, there were statistical difference in the positive rate among three experimental groups only at 1 day (P<0.05). (2) In the positive mice, their UU3 quantity concentration at 1, 3, 7, 14, 21 days were 1.70x10(7), 8.26x10(6), 4.04x10(6), 2.86x10(6), and 2.41x10(5) copy/g in group A; 3.75x10(6), 2.56x10(6), 1.37x10(6), 6.72x10(5), and 1.12x10(5) copy/g in group B, and 1.45x10(5), 1.07x10(5), 5.43x10(4), 4.68x10(3), and 0 copy/g in group C. There were statistical difference among experimental groups at all time points except 21 days (P<0.05). Comparing the concentration among all time points of every group, both group A and B showed a significant difference (P<0.05), group C didn't reach it (P>0.05). (3) The total pathogenicity rates of three groups were significant different at 7-35 days, which were 56% (18/32) in group A, 44% (14/32) in group B, 6% (2/32) in group C (P<0.01). And at 7, 14, 21, 35 days of postinoculation, the pathogenicity rates in group A were 5/8, 5/8, 4/8 and 4/8, group B were 4/8, 4/8, 3/8 and 3/8, group C were 1/8, 0, 1/8 and 0; all mice in control group were zero, which demonstrated significant difference only at 14 days (P<0.05), no other statistical difference were observed (P>0.05). CONCLUSIONS: The pathogenicity of UU3 varies with different concentration in genital tract of mice. When UU3 concentration is more than 1x10(6) copy/g, the susceptibility to infection was intensified significantly.