Clinical implications of detection of Ureaplasma urealyticum in the amniotic cavity with the polymerase chain reaction.

OBJECTIVE: The objective of this study was to determine the frequency and clinical significance of the detection of Ureaplasma urealyticum by means of the polymerase chain reaction with specific primers in the amniotic fluid of patients with preterm premature rupture of membranes. STUDY
DESIGN: Amniocentesis was performed in 154 patients with preterm premature rupture of membranes. Amniotic fluid was cultured for aerobic and anaerobic bacteria and for mycoplasmas. Ureaplasma urealyticum was detected by means of the polymerase chain reaction with specific primers. Patients were divided into the following 3 groups according to the results of amniotic fluid culture and polymerase chain reaction for U. urealyticum: those with a negative amniotic fluid culture and a negative polymerase chain reaction (n = 99), those with a negative amniotic fluid culture but a positive polymerase chain reaction (n = 18), and those with a positive amniotic fluid culture regardless of the results of the polymerase chain reaction (n = 37). Contingency table and survival techniques were used for analysis.
RESULTS: (1) U. urealyticum was detected by polymerase chain reaction in 28% (43/154) of patients and by culture in 16% (25/154). (2) Among the 43 patients with a positive polymerase chain reaction for U urealyticum, amniotic fluid culture was negative in 42% (18/43). (3) Patients with a negative amniotic fluid culture for U urealyticum but a positive polymerase chain reaction had a significantly shorter median interval from amniocentesis to delivery and a higher amniotic fluid interleukin 6 and white blood cell count than did those with a negative amniotic fluid culture and a negative polymerase chain reaction (interval to delivery; median, 53 hours; range, 0.3-335 hours; vs. median, 141 hours; range, 0.1-3552 hours; P<.05; amniotic fluid white blood cell count: median, 513 cells/mm(3); range, 1-2295 cells/mm(3); vs. median, 1 cell/mm(3); range, 0-7956 cells/mm(3); amniotic fluid interleukin 6: median, 16.6 ng/mL; range, 0.3-53.0 ng/mL; vs. median 0.4 ng/mL; range, 0-69.8 ng/mL; P<.0001 for all). (4) Patients with a positive polymerase chain reaction for U. urealyticum but a negative amniotic fluid culture had a higher rate of significant neonatal morbidity than did those with both a negative culture and a negative polymerase chain reaction (P<.05). (5) No significant differences in perinatal outcome were observed between patients with a negative culture but a positive polymerase chain reaction and those with a positive amniotic fluid culture.
CONCLUSION: (1) Culture techniques for mycoplasmas missed 40% of cases of microbial invasion of the amniotic cavity with U. urealyticum. (2) Patients with a positive polymerase chain reaction but a negative amniotic fluid culture are at risk for adverse outcomes. (3) The use of molecular microbiologic techniques is likely to increase the detection of infection among patients with obstetric complications.