Genital mycoplasmas and inhibitory substances in amniotic fluid: A negative result

Abstract

BECAUSE OF THE POTENTIAL importance of genital mycoplasmas as a cause of amnionitis, we cultured 50 amniotic fluid samples obtained at the time of routine amniocentesis for :~f~c~~fdasrnu hominis and Ureaplasma rr~crl$icum. In addition. we studied 25 amniotic fluid samples for inhibitory stubstances to either of these mycoplasmas. ,4mniotic fluids were kept at -70” C until they were thawed for culturing. After thawing the fluid was spun at 2,000 rpm for 10 minutes; 0.6 ml was removed from the bottom of the tube. and 0.2 ml was distributed into each of three vials: urea broth, urea broth with lincomycin, and arginine broth with erythromycin. Cultures were incubated at 37” C and checked twice daily for a color change consistent with a rise in pH. Such vials were subcultured onto mycoplasma agar. All .N specimens were negative for either mycoplasma species. In order to ascertain whether amniotic fluid might contain an inhibitory substance to genital mycoplasmas. filter paper disks. 6 mm in diameter, were impregnated with 25 ~1 samples of amniotic fluid and the disks were placed on plates which had been seeded with a known strain of ,Lf. hominis and I,‘. urc~alyticum. The 25 amniotic fluid samples selected for these experiments were derived from pregnancies of 15 to 43 weeks’ gestation with a mean of 35.5 weeks. These plates were incubated in an atmosphere of 90%’ nitrogen and 10% carbon dioxide and, beginning 23 hours after incubation, were inspected for anv inhibition of mycoplasma growth around the disks. None of the 25 amniotic fluid samples demonstrated any inhibition of either mycoplasma species. Chorioamnionitis has been associated with infant, but not maternal. colonization with U. urenlyticum.’ It is thought that amnionitis. which occurs with intact membranes. is mainly a result of invasion of these membranes in the area of the cervical OS. After rupture of membranes ,M. ho~fi~b has been cultured from amniotic fluid,’ but, just as we observed, Klein and Milunsky were unable to culture mycoplasmas from 32 amniotic fluid specimens. It might be surmised that the antibacterial polypeptide that has been found in amniotic fluid would also have a role in preventing the