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To the Editor:
We have read with interest Dr. John G. Bellows' letter on sterility and cryosurgery (Arch Ophthal74:290-291, 1965). Our experiences are consistent with his finding that cryogens are practically free of bacteria. We examined samples of liquid nitrogen by evaporating the samples under sterile conditions and subsequent determining germ count in the container. We found one living bacterium for every 5 to 10 ml of liquid nitrogen. It should be taken into account, however, that even the most dangerous bacteria are not at all impaired at the temperature of the liquid nitrogen. We added lyophilized cultures of Pseudomonas aeruginosa and Staphylococcus aureus thoroughly ground with talc to liquid nitrogen and determined the germ count in the container after the nitrogen had evaporated. The bacteria could be recovered in full number in both cases.We have drawn the conclusion that, in spite of the sterility (in the
Radnot M, Farkas E. STERILITY AND CRYOSURGERY. Arch Ophthalmol. 1966;75(2):302–303. doi:10.1001/archopht.1966.00970050304031
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