182 DISINFECTION OF DRY (VAPOR) SHIPPERS (“DEWARS”) FROM MICROBIAL CONTAMINATION ASSOCIATED WITH CRYOPRESERVED GERMPLASM

Abstract

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 liquid nitrogen (LN) dry (vapor) shippers used for short-term storage and transportation of germplasm and other biological specimens. Dry shippers containing either a hydrophobic or a nonhydrophobic 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 vapors of formalin and ethylene oxide were used for disinfection of the shippers. All biocide solutions were diluted with milli-Q water to the concentrations recommended by the manufacturer and poured directly into the chamber of the dry shippers. The dry shipper was filled with the disinfectant for 30 min, drained, washed three times with sterile water, and drained before testing the residue for microbial contaminant. Among the biocidals used, treatment with sodium hypochlorite solution (30% of household bleach), a quaternary ammonium-based disinfectant (100% Expel), and peracetic acid (30%) 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. Other disinfectants (Virkon, Roccal, 1-Stroke, Expel Odor) were not effective due to their foaming properties. Some other disinfectants (Viralex and 70% ethanol) caused irreversible damage to the permeability of the LN-absorbent hydrophobic membrane. Gas sterilization by ethylene oxide was effective for both types of dry shipper.

The author thanks Mr. A. Hanniman for his technical support and Ms. B. Phipps-Todd for processing samples for the scanning electron microscopy.