BCG vaccine bacilli that seemed less virulent, and changed the course of their research to see if repeated subculturing would produce a strain that was attenuated enough to be considered for use as a vaccine. The BCG strain was isolated after subculturing 239 times during 13 years from virulent strain on glycerine potato medium. The research continued throughout World War I until 1919, when the now avirulent bacilli were unable to cause tuberculosis disease in research animals. Calmette and Guerin transferred to the Paris Pasteur Institute in 1919. The BCG vaccine was first used in humans in 1921. Public acceptance was slow,
Inoculation needle the aseptic technique. An open flame from an incinerator, a bunsen burner, or an alcohol burner is used to flame along the tip and the length of the needle that is to be in contact with the inoculum. For ease of manipulation it is common practice to hold the needle with the dominant hand as if handling a pencil. The needle will be flamed at a downward angle through the flame’s inner cone until it is red-hot. The downward angle will minimize the amount of microbial aerosols created. Inoculation needles must be sterilized prior and following contact with microbial life