1/26/2016 Enterobacteriaceae Opportunistic Microorganisms Opportunistic pathogens Eschenchia col Some normal microbiota are opportunistic pathogens Klebsiella pneumoniae cause a dis r the Serratia marcescens certain circumstances Proteus spp. access through broken skin or mucous membrane Providencia spp. weakened host immune system -compromised immune system due to infection Obligate pathogens Symbiotic relationships can change under certain Saimonella spp. conditions Shigella spp Yersinia spp Some E coW strains The Etiology of Infectious Diseases Robert Koch-1876 Learning Objective List Koch's postulates. Discovered that Bacillus anthracis causes anthrax 1-isolated the strain in pure culture from blood of dead cattle 2-injected into a healthy animal 3-isolated the same bacteria from this dead animal latb2eweetatsRbeterosg tuber 61/26/2016 6 Opportunistic Microorganisms • Some normal microbiota are opportunistic pathogens • Defined: a microorganism that does not ordinarily cause a disease but can become pathogenic under the certain circumstances - access through broken skin or mucous membrane - weakened host immune system - compromis d i s st d t i f ti ised immune system due to infection • Symbiotic relationships can change under certain conditions The Etiology of Infectious Diseases Learning Objective List Koch's postulates. Robert Koch- 1876 Germ theory of diseases – proved that b t i s dis s bacteria cause disease Discovered that Bacillus anthracis causes anthrax 1-isolated the strain in pure culture from blood of dead cattle 2-injected into a healthy animal 3-isolated the same bacteria from this dead animal Later showed that Mycobacterium tuberculosis causes tuberculosis