Bacterial growth inhibition by amniotic fluid. VII. The effect of zinc supplementation on bacterial inhibitory activity of amniotic fluids from gestation of 20 weeks.

Twenty human amniotic fluids obtained from gestations of 20 weeks' duration supported bacterial growth. Nine of the 20 fluids could be made inhibitory by adjusting the phosphate to zinc ratios of the fluids to less than 200 mug per milliliter. These fluids contained the phosphate-sensitive bacterial inhibitor previously, but the fluids contained sufficient phosphate to inactivate the antibacterial system. The remaining 11 amniotic fluids did not contain the peptide component of the phosphate-sensitive bacterial inhibitor and could not be made inhibitory by adjusting the phosphate to zinc ratio to less than 200 mug per milliliter. The data obtained suggested synthesis of the peptide component may occur at a gestational age of approximately 20 weeks. The peptide may indirectly be detected in fluids by determining whether antibacterial activity is obtained when the phosphate to zinc ratio of the fluids is adjusted to less than 200 mug per milliliter.