Evidence that intra-amniotic infections are often the result of an ascending invasion – a molecular microbiological study

Microbial invasion of the amniotic cavity resulting in intra-amniotic infection is associated with obstetrical complications such as preterm labor with intact or ruptured membranes, as well as clinical and histological chorioamnionitis. The most widely accepted pathway for intra-amniotic infection is ascension of microorganisms from the lower genital tract. This is because the microorganisms most often detected in amniotic fluid are those that are typical inhabitants of the vagina. Yet, no studies have shown that microorganisms in the amniotic cavity are simultaneously present in the vagina of the woman from which they were isolated.

PRB researchers determined how frequent microorganisms isolated from women with intra-amniotic infection and intact membranes are also present in the lower genital tract. Microorganisms isolated from bacterial cultures of amniotic fluid were taxonomically identified through matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) and 16S rRNA gene sequencing. The broader bacterial profiles of amniotic and vaginal fluids were characterized through 16S rRNA gene sequencing. The majority of women with intra-amniotic infection had bacteria cultured from their amniotic fluid that were typical vaginal commensals, and these bacteria were detected within the vagina at the time of amniocentesis. Molecular microbiological interrogation of amniotic fluid revealed that the bacterial profiles of amniotic fluid were largely consistent with those of the vagina. Taken together, these findings demonstrate that ascension from the lower genital tract is the primary pathway for intra-amniotic infection.

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