Medical microbiology

1. Medical microbiology CLS 212

2. Introduction • What is microbiology? the branch of biology that studies microorganisms and their effects on humans • Microorganisms a collection of organisms that share the characteristic of being visible only with a microscope • contribute to the quality of human life o maintain the balance of chemical elements in nature o breakdown the remains of all that die o recycle carbon, nitrogen, sulfur, phosphorus and other elements • some cause infectious disease called Pathogenic o overwhelm body systems by sheer force of numbers o produce powerful toxins that interfere with body physiology o viruses inflict damage by replicating themselves within tissue cells causing tissue degeneration

3. Classification of Microorganisms • Taxonomy- the science of classification • Kingdom (5 major divisions) • Phylum (groups of related Classes) • Class (groups of related Orders) • Order (groups of related Families) • Family (groups of related Genera) • Genus (groups of related Species) • Species (living organisms that are alike) • The Five Kingdoms 1.Monera (unicellular prokaryotes: bacteria, cyanobacteria, blue-green algae) 2.Protista (unicellular eukaryotes: protozoa, unicellular algae, slime molds) 3.Fungi (multicellular eukaryotes: molds, mushrooms, yeasts) 4.Plantae (multicellular eukaryotes: plants) 5.Animalia (multicellular eukaryotes: animals) • Species • a population of individuals that breed among themselves • microorganisms that are 70% similar from a biochemical standpoint

4. Classification of Microorganisms Microorganisms and all other living organisms are classified as Prokaryotes and Eukaryotes. They are distinguished on the basis of their cellular characteristics. • Prokaryotes and Eukaryotes 􀂃 enclosed by cell (plasma) membranes 􀂃 use DNA for genetic information • Prokaryotes 􀂃 lack a nucleus 􀂃 lack organelles 􀂃 include bacteria and cyanobacteria (blue-green algae) • Eukaryotes 􀂃 have a nucleus 􀂃 have organelles 􀂃 include fungi, protozoa and simple algae • Viruses 􀂃 are neither Prokaryotes or Eukaryotes 􀂃 lack the characteristics of living things 􀂃 are able to replicate only in their host (living cells)

7. Historical Background • mid 1600s – English scientist Robert Hooke viewed cells and observed strands of fungi • 1670s – Dutch merchant Anton van Leeuwenhook made a simple one-lens microscope and observed and provided accurate descriptions of protozoa, fungi and bacteria • 1750-1760 – Carolus Linnaeus classified all known plants and animals and set down rules for classification • 1875-1900 – The Golden Age of Microbiology

8. Historical Theories • The Theory of Spontaneous Generation a long-held theory that life springs up from non-living or decaying organic matter, was based on observations of rotting food seemingly producing living organisms. Francesco Redi (1626-1678) was an Italian physician who showed that rotting meat carefully kept from flies will not spontaneously produce maggots. • The germ theory 1861: Louis Pasteur's famous experiments with swan-necked flasks finally proved that microorganisms do not arise by spontaneous generation • This led to: Development of sterilization

9. Historical Theories • Koch’s postulates 1890s: Robert Koch sets guidelines for how to prove that a particular microbial agent is responsible for a particular disease. Koch's postulates state that: • The suspect microorganism must be routinely isolated from patients with a particular illness; • The microorganism must be grown in pure culture in vitro; • When the pure culture is inoculated into a new host, it must cause the same illness; • The same microorganisms must be reisolated from new host.