Microbiology

Microbiology Study Guide

• Rudolf Virchow was a German scientist who first proposed the theory of biogenesis, which is the claim that cells arise from other cells. However, he was unable to prove his theory. • John Tyndall (1820-1893) demonstrated that dust did carry microbes and that if dust was absent, the broth remained sterile, even if it was directly exposed to air. Tyndall also provided evidence for the existence of heat-resistant forms of bacteria. • Agostino Bassi de Lodi (1835) showed that fungus was responsible for the disease affecting silkworms. This discovery marked the first microorganism to be identified responsible for a disease. • Louis Pasteur (1822-1895) played a major role in proving germ theory. He set up an experiment involving beef broth and open-ended, long neck flasks. All the flasks were filled with beef broth and boiled. After boiling, some were left open to air and others were sealed. Those that were sealed did not have microbes, while those left open contained microbes. He proved that the air contained microorganisms. He is credited for forming the basis for aseptic techniques. Pasture is also the founder of pasteurization, which heats a liquid to a specific temperature that will kill unwanted microbes and render the liquid safe to consume. This is a milestone accomplishment for the field of microbiology and allowed a direct link between microbes and the potential for causing disease. In addition, Pasteur identified a protozoan in 1865 that was responsible for silkworm disease. This was important at that time because silkworms were dying and the silk industry in Europe was suffering. Not only did he identify the protozoan, but he developed a method to determine which worms were afflicted. • Ignaz Semmelweis (1818-1865), a noted Hungarian physician, showed that doctors in Vienna hospitals were responsible for spreading puerperal (childbed) fever while delivering babies. He introduced infection control in the 1840s by having the doctors under his supervisionwash their hands between patient contacts. • In the 1860s Joseph Lister (1827-1912), an English surgeon, introduced antiseptics in surgery through the use of carbolic acid to clean and kill the bacteria on surgical instruments, wounds, and dressings. His success reduced surgical mortality due to bacterial infection and resulted in this practice being adopted by other surgeons. • Robert Koch (1843-1910) was a German bacteriologist. He was the first to cultivate the rod- shaped anthrax bacteria, Bacillus Anthrais, outside the body using blood serum (1876) and subsequently injected these bacteria into healthy cattle, resulting in the disease state. He subsequently published “Koch's Postulates” in 1884, which formed the critical test method for proof that a microorganism is the cause of a disease, although it should be noted that there are a few diseases that fall outside the postulates. “Koch's Postulates” states: o The pathogen must be present in every case of the disease. o The pathogen must be isolated and cultured in vitro. o The disease must be reproduced when a pure culture of the pathogen is inoculated into a susceptible host. o The pathogen must be recoverable from the experimentally-infected host. Discovery of Immunity Smallpox was endemic in China by 1000 B.C. With the understanding that survivors of smallpox were

©2018

Achieve

Page 8

of 132