Ureaplasma parvum or Mycoplasma hominis as sole pathogens cause chorioamnionitis, preterm delivery, and fetal pneumonia in rhesus macaques.

The authors assess causal, cellular and inflammatory links between intraamniotic infection with Ureaplasma parvum or Mycoplasma hominis and preterm labor in a nonhuman primate model. Long-term catheterized rhesus monkeys received intraamniotic inoculations of clinical isolates of Ureaplasma parvum serovar 1, M hominis, media control or physiological saline. Genital mycoplasmas were quantified in amniotic fluid (AF) and documented in fetal tissues by culture and PCR. In association with elevated AF colony counts for U parvum or M hominis, there was a sequential upregulation of AF leukocytes, proinflammatory cytokines, prostaglandin E2 and F2a, metalloproteinase-9 and uterine activity ( P< .05). Fetal membranes and lung were uniformly positive for both microorganisms; fetal blood and cerebrospinal fluid cultures and PCR were more often positive for M hominis than U parvum. Histopathologic findings of chorioamnionitis, a systemic fetal inflammatory response and pneumonitis worsen with duration of in utero infection. U parvum or M hominis, as sole pathogens, elicit a robust proinflammatory response which contributes to preterm labor and fetal lung injury.