Félix d'Hérelle (25 April 1873 – 22 February 1949) was a French microbiologist. He was co-discoverer of bacteriophages (viruses that infect bacteria) and experimented with the possibility of phage therapy. D'Hérelle has also been credited for his contributions to the larger concept of applied microbiology.
d'Hérelle was a self-taught microbiologist. In 1917 he discovered that "an invisible antagonist", when added to bacteria on agar, would produce areas of dead bacteria. The antagonist, now known to be a bacteriophage, could pass through a Chamberland filter. He accurately diluted a suspension of these viruses and discovered that the highest dilutions (lowest virus concentrations), rather than killing all the bacteria, formed discrete areas of dead organisms. Counting these areas and multiplying by the dilution factor allowed him to calculate the number of viruses in the original suspension. He realised that he had discovered a new form of virus and later coined the term "bacteriophage".Between 1918 and 1921 d'Hérelle discovered different types of bacteriophages that could infect several other species of bacteria including Vibrio cholerae. Bacteriophages were heralded as a potential treatment for diseases such as typhoid and cholera, but their promise was forgotten with the development of penicillin. Since the early 1970s, bacteria have continued to develop resistance to antibiotics such as penicillin, and this has led to a renewed interest in the use of bacteriophages to treat serious infections.
