During their journey through the female reproductive tract to reach the oocyte in the ampulla of the fallopian tube, spermatozoa interact with substances and microorganisms that affect sperm quality, thus altering their fertilizing capacity.To determine in vitro the effect of Streptococcus agalactiae, Klebsiella pneumoniae and their soluble factors on sperm parameters, and to evaluate the ability of human sperm to interact with and transport these bacteria.The effects of S. agalactiae, K. pneumoniae and their soluble factors on the viability, sperm motility and functional sperm parameters were quantified. In addition, motile spermatozoa were incubated with decreasing concentrations of bacteria for one hour, washed and post-infection treatments were performed with trypsin and transport capacity was assessed by quantitative cultures.Incubation of spermatozoa with K. pneumoniae decreased progressive motility. The soluble factors of K. pneumoniae increased the number of necrotic spermatozoa and the soluble factors of S. agalactiae increased lipid peroxidation of the sperm membrane (p<0.05). A strong interaction between sperm and bacteria was observed in the transport assays even in washed trypsin-treated samples.Human spermatozoa act as vectors for infections, generating strong interactions with K. pneumoniae and S. agalactiae favoring their diffusion through the female reproductive tract. This interaction affects male fertility by altering progressive motility, increasing the number of necrotic cells and inducing apoptosis.