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Richard Pfeiffer (1858-1945) was a German physician and bacteriologist. He is remembered for his many fundamental discoveries in immunology and bacteriology, including the phenomenon of bacteriolysis, later known as the Pfeiffer Phenomenon or Isayev-Pfeiffer phenomenon. Pfeiffer was a pioneer in typhoid vaccination. He discovered the specific bacteria-dissolving immune bodies in cholera and typhus. In 1892 he isolated what he thought was the causative agent of influenza, the Haemophilus influenzae bacteria, though this was later proven not to be the culprit. In 1896 he isolated micrococcus catarrhalis, the cause of laryngitis. M. catarrhalis also causes bronchitis and pneumonia in children and adults with underlying chronic lung disease. It is occasionally a cause of meningitis.