Researchers in 2024 detailed a case report of a patient with recurrent implantation failure as a result of bacterial contamination, which was resolved after removal of the zona.
๐ Original studies are referenced in this post or within the linked Remembryo posts.
๐ก Reminder: Terms underlined with a dotted black line are linked to glossary entries. Clicking these does not count toward your paywall limit.
Although embryo culture media is often supplemented with antibiotics, bacterial contamination can still occur. Some bacteria can attach to the zona of the embryo and potentially cause inflammation that prevents implantation.
To rescue embryos that have been contaminated, the embryologist can wash the embryo by transferring it to clean culture media supplemented with antibiotics, although this isnโt always successful.
Another method of removing bacteria from the zona is by using acidic Tyrodeโs solution (Li et al. 2022). This solution dissolves the zona, but it may not work well if the zona is thick, and thereโs a risk of exposing the embryo to the acid.
In a recent case study, Dang et al. (2024) removed the zona using a laser. This was the same laser they used for assisted hatching.
In the report, a patientโs embryos had been contaminated early in the IVF procedure. This caused her 5 euploid embryos to become contaminated, which persisted even after freezing in liquid nitrogen.
At the first transfer, the embryologist noticed that the culture media contained cloudy particles (the bacteria). They performed the transfer but sent off the media for testing, which found Rhizobium radiobacter bacteremia contamination.
Rhizobium radiobacter is commonly found in soil and has been associated with human diseases, including urinary tract infections.
The first euploid transfer failed. For the second and third transfer, the embryos were washed 4 times before transferring. These transfers also failed.
Finally, they decided to remove the zona from the embryo during the fourth transfer, which led to a successful pregnancy and a healthy live birth. Presumably, the bacteria was likely attached to the zona, and this caused problems with implantation.
This case report demonstrates the importance of the lab for IVF outcomes, and adds another reason embryos might fail to implant: IVF culture media contamination! For more reasons, check my post Why do embryos in IVF fail to implant or miscarry?
Reference
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About Embryoman
Embryoman (Sean Lauber) is a former embryologist and the founder of Remembryo, an IVF research and fertility education website. After working in an IVF lab in the US, he returned to Canada and now focuses on making fertility research more accessible. He holds a Masterโs in Immunology and launched Remembryo in 2018 to help patients and professionals make sense of IVF research. Sean shares weekly study updates on Facebook, Instagram, and Reddit regularly. He also answers questions on Reddit or in his private Facebook group.
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