It is used to test for toxigenicity of "C. diphtheriae" strains. The most notable human infection is diphtheria, caused by "C. diphtheriae". He used Koch's postulates to prove association between "C. diphtheriae" and diphtheria. Friedrich Loeffler was the first person to cultivate "C. diphtheriae" in 1884. The three main types of "C. diphtheriae" cause different severities of disease. Others can cause human disease, including most notably diphtheria, which is caused by "C. diphtheriae". In areas where diphtheria is endemic, "C. diphtheriae" in the nasopharyngeal passageways is common.