Microbial invasion of the amniotic cavity with Ureaplasma urealyticum is associated with a robust host response in fetal, amniotic, and maternal compartments

OBJECTIVE: Ureaplasma urealyticum is the microorganism most frequently isolated from the amniotic fluid of women with preterm labor and preterm premature rupture of the membranes, yet the significance of amniotic fluid infection exclusively caused by this microorganism is unclear. This study was conducted to examine the presence and intensity of the inflammatory response in the fetal, amniotic, and maternal compartments in patients with preterm premature rupture of membranes and amniotic fluid infection with U urealyticum. STUDY DESIGN: One hundred twenty patients with preterm premature rupture of the membranes who delivered preterm neonates (gestational age less than or equal to 36 weeks) within 5 days of amniocentesis were included. Amniotic fluid was cultured for aerobic and anaerobic bacterias and mycoplasmas. The intensity of the inflammatory response was evaluated by amniotic fluid concentrations of interleukin-6, tumor necrosis factor-alpha, interleukin-1 beta, amniotic fluid white blood cell count, histologic chorioamnionitis, and interleukin-6 concentrations of umbilical cord plasma at birth. Cytokines were measured by sensitive and specific immunoassays. RESULTS: The prevalence of a positive amniotic fluid culture in which the only microbial isolate was U urealyticum was 21% (25/120) and that of positive cultures with other or mixed microorganisms was 9% (11/120). Intrauterine inflammatory response was significantly more intense in patients with positive amniotic fluid cultures limited to U urealyticum than in those with a negative culture (median and range of amniotic fluid interleukin-6, 13.4 [0.7-115.2] ng/mL vs 0.9 [0.001-137.2] ng/mL; median and range of amniotic fluid tumor necrosis factor-a, 85.5 [0.9-1600] pg/mL vs 2.4 [0-1142] pg/mL; median and range of amniotic fluid interleukin-1 beta, 274.0 [0.3->80,000] pg/mL vs 3.4 [0-1449] pg/mL; median and range of amniotic fluid white blood cell count, 306 [0-19,764] cells/mm(3) vs 3 [0-7956] cells/mm3; median and range of cord interleukin-6, 20.0 [2.3-1199.6] pg/mL vs 6.7 [0-5550] pg/mL; histologic chorioamnionitis, 100% [22/22] vs 42% [30/72]; P < .01 for each) but was similar to values of patients with a positive amniotic fluid culture for other bacteria or mixed microorganisms. CONCLUSION: Patients with preterm premature rupture of membranes and microbial invasion of the amniotic cavity with U urealyticum are associated with a robust host inflammatory response in the fetal, amniotic, and maternal compartments.