In vitro effect of Escherichia coli on human sperm acrosome reaction

Escherichia coli are known to reduce human sperm motility. The purpose of the present study was to examine whether these bacteria may also affect the acrosome reaction, which is another important sperm function. The acrosome reaction was determined in spermatozoa from 29 fertile men by triple stain after 3-h incubation at 37 degrees C with 2 x 10(6) E. coli/mL or without bacteria (control). Each sample was treated with 0.1% DMSO (spontaneous acrosome reaction) or calcium ionophore A23187 (induced acrosome reaction) for 1 h at 37 degrees C. The inducibility of the acrosome reaction was significantly lower in semen samples pretreated with E. coli than in the control samples (9.8 +/- 4.2% vs. 12.7 +/- 5.3%; p < .05). The results demonstrate that E. coli affect the inducibility of the acrosome reaction in vitro and may impair the fertilizing capacity of human spermatozoa.