Antimicrobial Effect of Amniotic Fluid

Abstract

The antimicrobial effect of amniotic fluid (AF) obtained during the first (AF₁) and second (AF₂) trimesters was compared with the third (AF₃) against anaerobic bacteria, such as Bacteroides fragilis ss. fragilis (6 strains), Eubacterium lentum (3 strains), and Peptostreptococcus anaerobius (4 strains). Escherichia coli (5 strains) served as a positive control. AF, supported the growth of all 4 anaerobes (except B fragilis for 4 hours) for the entire 24-hour period tested. AF₂ supported the growth of E coli and B fragilis for 24 hours but temporarily inhibited P anaerobius and E lentum. In contrast, AF₃ inhibited all bacteria tested for 8 hours or more. It is concluded that AF, is the least inhibitory, AF₃ the most, and AF₂ intermediate for the organisms tested. Lack of antimicrobial effect of AF on anaerobic bacteria may be one explanation for the higher incidence of anaerobic infections during absortion than during the prenatal period.