Detection of bacteria in placental tissues obtained from extremely low gestational age neonates.

The objective of the study was to quantify and identify aerobic and anaerobic bacteria as well as Mycoplasma and Ureaplasma in the chorionic parenchyma. A sample of the chorionic parenchyma from neonates delivered between 23-27 completed weeks was cultured and tested by polymerase chain reaction (PCR) methods using universal bacterial primers for the presence of bacteria and mycoplasmas. The culture positive rate was higher for vaginal deliveries (333/489; 68%) than for cesarean sections (363/876; 41%). Thirty percent of all culture-positive samples had only aerobic bacteria, 21% of the samples had only anaerobic bacteria, and 9% of the samples had only Mycoplasma/Ureaplasma. The mean concentration of Mycoplasma/Ureaplasma (4.00 +/- 1.11 log10 CFU/g) was significantly higher (P < .001) than the total count of either aerobes (3.24 +/- 1.12 log10 CFU/g) or anaerobes (2.89 +/- 0.99 log10 CFU/g). Staphylococcus sp. and Corynebacterium sp. as well as organisms associated with bacterial vaginosis were the most frequently recovered. A PCR product was not detected from either randomly selected or known culture-positive samples. Approximately half of second-trimester placentas harbor organisms within the chorionic plate. The chorion parenchyma appears to harbor constituents that prevent the identification of bacterial deoxyribonucleic acid by PCR methods.