Do mycoplasmas inhibit the human sperm fertilizing ability in vitro?

Although clinical observations have suggested that Ureaplasma urealyticum may be associated with reproductive failure, the role of ureaplasmas in human infertility remains controversial. However, the mechanism whereby ureaplasmas can interfere with the fertilization process is not known. To study possible mechanisms, we used the human sperm-hamster egg fertilization test. Eggs were exposed to the spermatozoa preincubated with Mycoplasma hominis or U. urealyticum (serotype 1-8). U. urealyticum serotype 4 showed greater interference activity on the penetration rate (6.6%) than did the other mycoplasmas, as compared with the control (55%). Furthermore, our data suggest that the inhibition of penetration was not related to a masking of sperm membrane sites, since the mean of adsorbed spermatozoa/egg after preincubation of spermatozoa with mycoplasmas was not significantly different from that of the control. In addition, eggs preincubated with U. urealyticum serotype 4 gave a reduction of the penetration rate by untreated spermatozoa.