Non-transmission of bacterial and viral microbes to embryos and semen stored in the vapour phase of liquid nitrogen in dry shippers

Cryopreservation and storage of germplasm is an important factor in the prevention of disease transmission by embryo transfer and artificial insemination. Here we report the results of an investigation on transmission of selected bacterial and viral pathogens by the vapour phase of liquid nitrogen (VPLN) to embryos and semen in dewars designed for short-term storage and transportation of biological specimens. In this study transmission of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, BVDV, and BHV-1 was examined from: (1) contaminated dry shippers to germplasm; (2) between contaminated and non-contaminated cryopreserved germplasm; and (3) between stock culture of pathogenic agents and germplasm. Contaminated and non-contaminated samples of embryos and semen were stored in proximity in the vapour phase LN in open containers for 7 days prior to testing for the presence of microbes. The results showed that there was no cross-contamination from either the contaminated dewars to germplasm or between contaminated and non-contaminated samples of embryos and semen during 7 days storage under LN vapours. The outcome of our investigation indicates that VPLN is a safe means for short-term storage of embryos and semen in dry shipper dewars commonly used for transportation of bovine germplasm.