Although Louis Pasteur famously developed pasteurization to kill harmful bacteria in wine in 1864, a half century later—in 1913, when bacteriologist Alice Evans began her career at the US Department of Agriculture’s dairy division—pasteurization of milk was still not mandatory. Evans started out studying common milk-borne bacteria, particularly Bacillus abortus, which can cause spontaneous abortion of bovine fetuses. At the time, just a few studies hinted that the bacterium could be harmful to human health, and the link was far from certain. Still, “the idea of drinking milk contaminated with bacteria capable of causing disease in animals was distasteful to me,” Evans recalled in the unpublished memoir she wrote in 1963. That hunch led her to question whether B. abortus was related to any bacterial species that cause disease in humans.
Talking with a USDA colleague, Evans learned about Micrococcus melitensis, a bacterium that in humans causes undulant or Malta ...
