The Effect of Reduced Bacterial Dilution on Human Amniotic Membrane Antibacterial Activity, in Vitro

Background : The human amniotic membrane is the inner most layer of placenta and has antimicrobial effect, due to the presence of human beta-defensins and elafins. The purpose of this study is to investigate the effect of dilution reduction of 0.5 McFarland prepared from standard bacterial strains of Salmonella enterica BAA-708, Escherichia coli ATCC25922, Pseudomonas aeruginosa ATCC27853, Klebsiella pneumoniae ATCC7881, and Enterococcus faecalis ATCC29212 on antibacterial effect of human amniotic membranes in vitro.
Materials and Methods : The amniotic membranes were obtained from the bank of organ transplantation in Imam Khomeini hospital, of women with elective cesarean section whose HIV, HBV, HCV and VDRL serological tests were negative. They were cut to 1.5×1.5 cm pieces. Then 0.5 McFarland suspensions of 1.5×108, 0.5×107 and 1.5×106 dilutions were prepared from bacteria which then were spread on Mueller Hinton medium agar and a piece of membrane was put in the center of each plate. After 24 hours incubation at 37ᵒC, the results were observed.
Results : In 0.5 McFarland standard dilution an inhibition zone was created in three standard strains of Pseudomonas aeruginosa, Escherichia coli, and Salmonella enterica unlike the other two strains. There was no change in the above results with two other dilutions and inhibition zone of sensitive strains was not created.
Conclusion : Dilution reduction of microbial strains does not affect the antibacterial impact of amniotic membrane and dilution reduction does not yield to a false positive response and the conversion of resistant to sensitive strains.