Ability of Escherichia coli to produce hemolysis leads to a greater pathogenic effect on human sperm

Objective: To determine the effect on human sperm of Escherichia coli strains separated on the basis of their ability to produce hemolysis. Design: Experimental study. Setting: University-based laboratory. Patient(s): Semen samples from healthy donors. Intervention(s): Five million sperm, selected via the swim-up method, were incubated with 3 E. coli concentrations to obtain ratios of sperm to E. coli of 1: 2, 1: 16, and 1: 128. The E. coli strains were: a hemolytic isolated strain (H), a nonhemolytic American Type Culture Collection strain (NH-ATCC), and a nonhemolytic isolated strain (NH-I). Main Outcome Measure(s): Aliquots of human sperm were used to measure progressive motility using computer-aided sperm analysis, mitochondrial membrane potential (Delta Psi m) with a JC-1 (5,50,6,60 tetrachloro-1,10,3,30-tetraethylbenzamidazolocarbocyanin iodide) and propidium iodide stain, and intracellular reactive oxygen species (iROS) with a dihydroethidium (DHE) stain. Sperm Delta Psi m and iROS were measured by flow cytometry. Sperm vitality was considered the mean of propidium iodide-negative and DHE-negative cells. Result(s): Sperm incubated with the H strain in a 1: 2 sperm to bacteria ratio demonstrated a significant decrease in motility and Delta Psi m, and an increase of iROS. The NH-ATCC strain decreased sperm motility and Delta Psi m, but in a ratio of sperm to bacteria of 1: 128; it increased iROS at a ratio of 1: 16. The NH-I strain did not affect the analyzed sperm functions, even at a 1: 128 sperm to bacteria ratio. Conclusion(s): Results show a greater pathogenic effect on human sperm of E. coli strains with, versus without, hemolytic capacity. (C) 2015 by American Society for Reproductive Medicine.