Effect of Mycoplasma bovis and Mycoplasma bovigentalium in semen on fertilization and association with in vitro produced morula and blastocyst stage embryos

Frozen-thawed bovine semen contaminated with Mycoplasma bovis (M. bovis) or Mycoplasma bovigenitalium (M. bovigenitalium) at either a high (10(6) CFU/ mL) or low (10(4) CFU/mL) concentration was used for bovine oocyte insemina tion. The resulting embryos were washed 10 times as recommended by the inte rnational Embryo Transfer Society (IETS) prior to isolation of agent. A tot al of 1494 oocytes was inseminated with contaminated sperm cells and 855 oo cytes with uninfected control semen. There was a significantly higher propo rtion of embryos that developed to the blastocyst stage in control than in the mycoplasma exposed groups (P<0.05), isolation of motile spermatozoa by swim-up procedure prior td insemination did not render sperm cells free of Mycoplasma SM. Although M. bovis was isolated from all washed embryos after the high exposure level, it was found in only 60% of the samples after the low exposure level. In contrast, M. bovigenitalium was isolated from 70 an d 12% of washed embryos exposed to the high and low levels of microorganism , respectively. Using scanning electron microscopy, both microorganisms wer e detected in association with the surface of zona pellucida-intact embryos and with sperm cells. These results indicate that mycoplasmas present in s emen can be transmitted through the IVF system acid infect embryos. Further more, the experiments showed that supplementation of culture media with sta ndard antibiotics and washing embryos as recommended by IETS were not effec tive in rendering IVF embryos free from M. bovis and M. bovigenitalium. (C) 2000 by Elsevier Science Inc.