How Germs get used to Antiseptics - 1921
VARY YOUR ANTISEPTICS; otherwise the disease germs will get used to them. The distinguished French physician and bacteriologist, Charles Richet, has recently laid before the French Academy of Sciences a note on researches made by him, together with Henry Cardot, on acquired characteristics and heredity in microbes. He experimented, among other things, on the influence of antiseptics, to determine especially whether bacteria may acquire immunity to toxic substances in the same manner that the higher animals do. His studies have been especially concerned with the bacteria of milk for the reason that these are readily cultivated, reproduce rapidly and possess properties which make it easy to estimate their activity by observing their power to produce lactic acid. Says the Comptes Rendus of the academy in part:
"It was found that the bacteria are sensitive to extremely small doses of poison, but, that, on the other hand, they rapidly become accustomed to the toxic medium and flourish well therein, altho bacteria not thus accustomed quickly perish. By multiplying and varying their experiments Richet and Cardot found that the immunity thus produced bore a definite relation to the quantity of the poisonous substance. This immunity is not produced when the poison is bichloride of mercury—on the contrary, the bacteria appear to be less resistant.
"The immunity is specfic; for instance, bacteria accustomed to sulphate of thallium become immune to this substance alone and not to other poisons. The acquired immunity persists; that is, when a race of bacteria which has become accustomed to thallium sulphate is afterwards cultivated in a normal medium, it retains its immunity for a varying length of time. If the immunity was acquired by months of contact with the poisonous substance, it persists longer than if it is the result of only a few days' habituation to the poison. In other words, the acquired immunity is only temporary.
"The immunity does not appear gradually, but abruptly. Furthermore, it does not appear to strengthen the general vigor; on the contrary, microbes which have been rendered immune appear to be particularly feeble in other respects. At the same time their fermentative capacity is enhanced, developing as the concentration of the poison increases. On the other hand, their fertility is diminished.