IMPROVED CLEAVAGE RATE OF HUMAN EMBRYOS CULTURED IN ANTIBIOTIC-FREE MEDIUM

Retarded development and blastomere fragmentation of human preimplanta tion embryos represent a common phenomenon in in-vitro culture systems , Even though media composition is generally formulated to meet embryo nutritional requirements, the influence of antibiotic supplementation has not been investigated thoroughly, The present study was performed to evaluate the effects of antibiotics on embryo morphology and growt h in modified culture media, A total of 196 zygotes from 18 couples ma s cultured in three different media: (i) conventional medium (II = 99, control group); (ii) medium modified with half the standard antibioti c concentration (rt = 54); and (iii) antibiotic-free medium (n = 43); 49 embryos from the control group were selected at the zygote stage an d transferred to the patients on day 2, The remaining 147 zygotes were cultured to the blastocyst stage for cryopreservation; their morpholo gy and cell number were assessed daily at 40, 64, 88, and 112 h post-i nsemination. Overall cleavage rate was 95% and embryo scoring revealed 91% grade 1 embryos throughout the culture period in the three media. Significantly higher cleavage rates were obtained in the antibiotic-f ree medium at each observation, including the blastocyst stage, when c ompared to the other two groups, In addition, no notable improvement w as observed in the embryos cultured in a reduced concentration of anti biotics, In conclusion, antibiotic supplementation of media has an adv erse effect on the growth rate of preimplantation embryos, even in red uced concentrations, suggesting that antimicrobial drugs may interfere with the timing of cleavage events either by delaying or blocking emb ryo development.