The antibiotic streptomycin assessed in a battery of in vitro tests for reproductive toxicology

Streptomycin is one of the most widely used antibiotics and is frequently added to cell culture media to prevent bacterial growth. We tested streptomycin in a battery of in vitro assays for assessment of reproductive toxicity. The follicle bio-assay (FBA) is a multiparametric long-term follicle culture system mimicking ovarian function; in vitro fertilisation (IVF) of exposed oocytes enables gamete quality determination through fecundability; the mouse embryo assay (MEA) analyses pre-implantation embryo development whereas the embryonic stem cell test (EST) studies post-implantation embryotoxicity. The FBA revealed a concentration-dependent decrease in oocyte nuclear maturation during continuous exposure from 50 μg/ml streptomycin onwards, characterised by a significantly reduced polar body-rate (40% vs. 92% in the control group). Oocytes that remained arrested in metaphase I (germinal vesicle breakdown) had aberrant spindle formation. IVF of long-term exposed oocytes in the FBA to 50 μg/ml streptomycin resulted in a significantly lower fertilisation rate of 23% vs. 74% in the control group and were unable to develop to the blastocyst stage. The MEA revealed no effect at pre-implantation embryo development and quality. Furthermore, no embryo-toxic effects of streptomycin were observed in the EST. In conclusion, oocytes are vulnerable to streptomycin treatment. Long-term exposure might cause fertility problems in the female and caution should be taken using streptomycin in cell culture media for assisted reproductive technology (ART).