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 c linical 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 prem ature rupture of membranes. Amniotic fluid was cultured for aerobic and ana erobic bacteria and for mycoplasmas. Ureaplasma urealyticum was detected by means of the polymerase chain reaction with specific primers. Patients wer e 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 polyme rase chain reaction (n = 18), and those with a positive amniotic fluid cult ure regardless of the results of the polymerase chain reaction (n = 37). Co ntingency 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 pati ents with a positive polymerase chain reaction for U urealyticum, amniotic fluid culture was negative in 42% (18/43). (3) Patients with a negative amn iotic fluid culture for U urealyticum but a positive polymerase chain react ion had a significantly shorter median interval from amniocentesis to deliv ery and a higher amniotic fluid interleukin 6 and white blood cell count th an did those with a negative amniotic fluid culture and a negative polymera se chain reaction (interval to delivery; median, 53 hours; range, 0.3-335 h ours; 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 interle ukin 6: median, 16.6 ng/mL; range, 0.3-53.0 ng/mL; vs median 0.4 ng/mL; ran ge, 0-69.8 ng/mL; P < .0001 for all). (4) Patients with a positive polymera se chain reaction for U urealyticum but a negative amniotic fluid culture h ad 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 pati ents with a negative culture but a positive polymerase chain reaction and t hose with a positive amniotic fluid culture. CONCLUSION: (1) Culture techniques for mycoplasmas missed 40% of cases of m icrobial invasion of the amniotic cavity with U urealyticum. (2) Patients w ith a positive polymerase chain reaction but a negative amniotic fluid cult ure are at risk for adverse outcomes. (3) The use of molecular microbiologi c techniques is likely to increase the detection of infection among patient s with obstetric complications.