Background Intra-amniotic
inflammation, which is associated with adverse pregnancy outcomes, can occur in the presence or absence of detectable microorganisms, and involves activation of the
inflammasome. Intra-amniotic
inflammasome activation has been reported in clinical
chorioamnionitis at term and
preterm labor with intact membranes, but it has not yet been investigated in women with preterm prelabor
rupture of membranes (preterm PROM) in the presence/absence of detectable microorganisms. The aim of this study was to determine whether, among women with preterm PROM, there is an association between detectable microorganisms in amniotic fluid and intra-amniotic
inflammation, and whether intra-amniotic
inflammasome activation correlates with microbial burden. Methods Amniotic fluids from 59 cases of preterm PROM were examined for the presence/absence of microorganisms through culture and
16S ribosomal RNA (rRNA) gene quantitative real-time polymerase chain reaction (qPCR), and concentrations of
interleukin-6 (IL-6) and ASC [apoptosis-associated spec-like
protein containing a caspase recruitment domain (CARD)], an
indicator of
inflammasome activation, were determined. Results qPCR identified more microbe-positive amniotic fluids than culture. Greater than 50% of patients with a negative culture and high
IL-6 concentration in amniotic fluid yielded a positive qPCR signal. ASC concentrations were greatest in patients with high qPCR signals and elevated
IL-6 concentrations in amniotic fluid (i.e. intra-amniotic
infection). ASC concentrations tended to increase in patients without detectable microorganisms but yet with elevated
IL-6 concentrations (i.e. sterile intra-amniotic
inflammation) compared to those without intra-amniotic
inflammation. Conclusion qPCR is a valuable
complement to microbiological culture for the detection of microorganisms in the amniotic cavity in women with preterm PROM, and microbial burden is associated with the severity of intra-amniotic inflammatory response, including
inflammasome activation.