Infertility is increasingly common worldwide. Sometimes the causes are in the male organism and can be due to hormonal disorders, inability of spermatozoa to penetrate the fallopian tubes, impaired production of spermatozoa and infections of the genital organs. It has been found that these infections are the cause of 10% of infertility cases. A study conducted by Pathogens has shown the impact of Escherichia coli infection on sperm quality. Most infections are caused by staphylococci, streptococci, enterococci, but E.coli is the cause of almost 80% of cases of bacterial prostatitis. This bacteria affects the functions of sperm and their ability to fertilize an egg. This involves a change in sperm motility as the egg and sperm fuse upon contact with the carbohydrate residues on the cell surface of E.coli, which are found mainly on its type 1 and P cilia. Type P cilia, in contact with galactosyl residues on the surface of the spermatozoon, cause its head and tail to stick together. Type 1 cilia, upon contact with mannose residues on the sperm surface, are associated with fusion of the two sperm heads. Another reason for reduced motility or absolute immobilization of spermatozoa is due to reduced function of their mitochondrial membrane in contact with bacteria. This contact damages the sperm head, its ability to penetrate the egg, and is associated with increased destruction of male gametes. Also, the increased level of free radicals causes damage to the lipid membranes of spermatozoa and their genetic material. The study tracked the impact of sperm contact with E.coli’s outer membrane vesicles, which contain, among other things, factors related to their ability to cause infection – proteins and toxins. These blisters protect the bacteria from the body’s immune defenses, deliver toxins and other immunomodulators. For the purpose of the study, such bubbles isolated from E.coli were added to samples of seminal fluid for a period of 30 to 90 minutes. Sperm motility, viability and structure were then assessed. Sperm functions were found to be decreased after contact within 45 minutes. After 90 minutes, motile spermatozoa predominated in the samples. In addition, these bubbles caused the accumulation of free radicals in the cervix of the spermatozoon, and after 90 minutes, their concentration was already 40%. Longer contact time was also associated with increased DNA damage. However, no change in the morphology of the spermatozoa was detected, which is most likely explained by their difficult observation due to the covering with these membrane bubbles. One hour contact was found to result in increased cell death. The accumulation of free radicals, in turn,it reduces the motility and flexibility of spermatozoa and disrupts the production of energy necessary for movement, which is synthesized in the mitochondria located in the neck. References: https://www.mdpi.com/2076-0817/11/7/782