Survival of bacteria after freezing of human semen in liquid nitrogen

Thirty-four semen samples from fertile men were subjected to bacteriologic evaluation before and after freezing to -196 degrees C using 10% glycerol as the protective medium. Cultures of the fresh portions from all ejaculates examined showed the presence of aerobic bacteria. Staphylococcus epidermidis, Corynebacterium sp., alpha-streptococci, and nonhemolytic streptococci were found so commonly that they were considered commensals. Enterococci, Escherichia coli, S. aureus, and beta-hemolytic streptococci group B, as well as Pseudomonas aeruginosa, P. maltophilia, and P. fluorescens, were also recovered from a few semen samples of these fertile men. Practically all bacteria isolated from the fresh ejaculate were also recovered from the portions frozen in liquid nitrogen.