Experimental microbial contamination and disinfection of dry (vapour) shipper dewars designed for short-term storage and transportation of cryopreserved germplasm and other biological specimens.

Cryopreservation, storage and transport of cryopreserved germplasm without the risk of disease transmission is of great concern to animal and human health authorities. Here we report on the efficacy of microbial decontamination of the liquid nitrogen (LN) dry (vapour) shippers used for short-term storage and transportation of germplasm and other biological specimens. Dry shippers containing either a hydrophobic or a non-hydrophobic LN absorbent were experimentally contaminated with high titers of cultures of Pseudomonas aeruginosa, Escherichia coli, Staphylococus aureus, bovine viral diarrhea virus (BVDV) and bovine herpesvirus-1 (BHV-1). Biocidals with broad spectrum antimicrobial activity and gas vapours of formalin and ethylene oxide were used for disinfection of the dewars. Among the biocidals used, treatment with sodium hypochlorite solution, the quaternary ammonium-based disinfectants and peracetic acid were the most effective and useful for dry shippers with a hydrophobic LN absorbent. None of the bacterial or viral microorganisms were detected in samples of semen and embryos stored in dry shippers following their disinfection with these biocides. An application of some other disinfectants, due to their foaming properties or to the permeability of the absorbent hydrophobic membrane (HM) was not effective or may have caused irreversible damage to the LN absorbent. Gas sterilization by ethylene oxide in contrast to formalin was fully effective for both types of dry shippers.