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 slant culture to needle, the open end of the culture will be treated with flame and the cap will be replaced. An inoculation needle is used in the transfer of microbial organisms from plate culture to needle by first sterilizing the needle to prevent contaminants. The lid of the agar plate culture is then removed to allow the needle access to the microorganisms cultured on the agar plate. The lid is held hovering above the culture plate to prevent contamination from the surrounding environment. The inoculation needle after incineration is cooled down on an uninoculated region of the agar plate