1512 BACTERIA CAUSING A FALSE POSITIVE TEST FOR PHOSPHATIDYLGLYCEROL (PG) IN AMNIOTIC FLUID

Abstract

Measurement of amniotic fluid PG is often used to assess fetal lung maturation. We documented three cases of chorioamnionitis where PG was present despite L/S ratios indicative of pulmonary immaturity. In one case PG was present in a vaginal pool specimen yet absent in a specimen obtained via amniocentesis. We hypothesized that bacterial organisms present may be responsible for the production of PG. E. coli isolated from amniotic fluid and neonatal blood was cultured in broth. One ml of 10⁵ colony forming units (CFU) per ml of E. coli was added to 4 ml of broth. One ml samples were removed at 0, 2, 3, and 4 hours and frozen at -65°C until phospholipid analysis was performed. A sample of broth containing no bacteria served as control. Specimens were analyzed for the presence of PG by a one dimensional thin-layer chromatographic (TLC) method. Postive test results were confirmed by two dimensional TLC. PG was present in cultured specimens at 3 and 4 hours incubation (270 × 10⁶ and 4000 × 10⁶ CFU, respectively). Broth alone and at 0 and 2 hours (2 × 10⁶ and 110 × 10⁶ CFU) contained no detectable PG. It appeared that more PG was present in the specimen incubated the longest. We conclude that bacteria regarded as normal flora can produce PG in detectable amounts and patients with amniotic fluid samples contaminated by growing bacteria may have detectable PG secondary to bacterial rather than fetal production of PG. These observations may weaken the usefulness of PG detection as predictive of lung maturity in patients with amniotic fluid samples contaminated by bacteria.

Log in or create a free account to read this content

Gain free access to this article, as well as selected content from this journal and more on nature.com

Access through your institution

or

Sign in or create an account

Continue with Google

Continue with ORCiD