A new method to rescue embryos contaminated by bacteria

Case Report

VOLUME 3, ISSUE 2, P168-171, JUNE 01, 2022


Ruiqi Li, Ph.D., Fengjiao Du, B.D., Songbang Ou, B.D., Nengyong Ouyang, Ph.D., Wenjun Wang, Ph.D. 



To report a case of successful pregnancy involving embryos that wereaffected by bacterial contamination.


A case report.


Academic assisted reproductive center.


A 31-year–old infertile patient with obstructed fallopian tubes facing bacterial contamination in her embryos during in vitro fertilization.


The zona pellucida (ZP) of the embryos that was contaminated by bacteria was removed by acidic Tyrode’s solution. The ZP-free embryos were then cultured in a time-lapse culture dish with 1 zygote per well until day 5 when a single ZP-free blastocyst was selected for transfer.

Main Outcome Measure(s)

The rate of obtaining embryos without recurrence of bacterial contamination and the developmental potential of the embryos.


Twenty oocytes were retrieved and were coincubated with sperm in vitro overnight. A total of 9 zygotes with 2 pronuclei and 3 zygotes with 1 pronucleus were obtained. Unfortunately, all zygotes were contaminated by the Klebsiella pneumoniae bacteria. The ZP of 7 zygotes were removed using acidic Tyrode’s solution (ZP-free group), whereas the remaining 5 zygotes and 3 metaphase II (MII) stage oocytes were washed with G-1 PLUS medium multiple times (washing treatment group). In the washing treatment group, all embryos experienced recontamination on day 2 and were dead by day 3. In the ZP-free group, 2 embryos were found to be recontaminated on day 2. The remaining 5 embryos that stayed uncontaminated were selected for blastocyst culture. On day 5, 2 of the cultured embryos developed into blastocysts. One blastocyst was transferred during the fresh cycle, and the other was vitrified. A single intrauterine gestation was confirmed 4 weeks after the transfer. At the time of writing this article, the patient was 30 weeks pregnant without any occurrence of intrauterine infection during pregnancy.


Zona pellucida removal is a safe and effective method to rescue embryos contaminated with bacteria.