[A study on the antibacterial activity of amniotic fluid--the significance of intraamniotic transferrin]

In order to study the antimicrobial activity of amniotic fluid, attempts were made to evaluate the in vivo growth of bacteria in amniotic fluid and the role of transferrin in antibacterial activity. The bacteria chosen for these experiments were Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Streptococcus faecalis, respectively. The results obtained were as follows: Amniotic fluid was shown have an antibacterial effect on Escherichia coli and Staphylococcus aureus, while Pseudomonas aeruginosa and Streptococcus faecalis proliferated readily in amniotic fluid. Individual difference in each sample appeared to be responsible for the inconsistent potency of the inhibitory effect observed. When amniotic fluid was heated at 100 degrees C for 5 minutes, the antibacterial activity was lost. The level of transferrin in amniotic fluid obtained at term was determined to be 29.1 +/- 17.6mg/dl (N = 90). The value correlated with neither those measured in cord sera nor maternal sera. The antimicrobial activity was restored by adding transferrin into heat-treated amniotic fluid at a concentration of 250mg/dl or higher. Simultaneous addition of transferrin and a sufficient concentration of iron made it possible to form a transferrin-iron complex. A subsequent decrease in unbound transferrin resulted in the loss of antibacterial properties.