Microorganisms Pathogenic to Man​ (lab)

• Pathogenic bacteria -  bacteria that can cause disease
• Susceptibility - is the extent to which an organism or ecological community would suffer from a threatening process or factor if exposed, without regard to the likelihood of exposure.
• Pathogen -  infectious agent is a biological agent that causes disease or illness to its host
• Pathology - study of disease
• Etiology:  Cause of disease; often microbial​

  Flu – etiological agent, Influenza virus​

  Tb – M. tuberculosis​
• Pathogenesis:  development of disease in the host -  Norwalk virus; Fecal – oral, diarrhea​
• Disease:  altered state of health, host body is ​

  changed, upset of homeostasis​
• Epidemiology:  Science of the study of how diseases are acquired and spread in a population​
• Infectious disease - a disease caused by an organism or virus that enters and multiplies within the human body.​
• Toxins - A poison given off by some bacteria that can injure cells.
• Virus - The smallest type of pathogen​
• Bacteria - Simple, single-celled microorganisms​
• Microorganisms - An organism that is so small it can only be seen through a microscope.​
• Immunogenicity - the ability to induce an immune response in the host​
• Infectivity - the ability to infect a host​
• Virulence - The ability of an agent of infection to produce disease
• Host -  an animal or plant on or in which a parasite or commensal organism lives.​
• Diagnosis - the art or act of identifying a disease from its signs and symptoms​
• Mode of transmission - is the route or method of transfer by which the infectious microorganism moves or is carried from one place to another to reach the new host.​
• The modes (means) of transmission are:

  Contact (direct and/or indirect), Droplet, Airborne, Vector and Common Vehicle. ​
• Loius Pasteur - accepted a task to investigate a disease of the silkworm that was ravaging France’s silk industry. This work contributed to Pasteur’s growing interest in infectious disease
• Giardia lamblia:


  Giardiasis is a disease caused by infection with the protozoan Giardia lamblia. Infection with Giardia can produce diarrhea, gas, and abdominal pain in some people.
• Leeuwenhoek:

  who found the parasite in his own {diarrheal} stools, Giardia lamblia was first discovered
• Louis Pasteur​:

  • The more formal experiments on the relationship between germ and disease were conducted by Louis Pasteur between the year 1860 and 1864. ​
  • He discovered the pathology of the puerperal fever and the pyogenic vibrio in the blood, and suggested using boric acid to kill these microorganisms before and after confinement.​
• Carlos Finlay Identifies a Suspect​:

  • Carlos Finlay (1833-1915) presented the paper “The Mosquito Hypothetically Considered as the Transmitting Agent of Yellow Fever”—the first to correctly identify mosquitoes as the ultimate source of the disease.​
• Bacterium Identified Edwin Klebs (1834-1913)


  ,a Swiss-German pathologist, identified and described the bacterium that causes diphtheria. It was known at first as the Klebs-Loeffler bacterium.​
• Friedrich Loeffler 

  • a German bacteriologist was the first to cultivate Corynebacterium diphtheriae.​
  • Loeffler used a set of rules we now know as Koch's postulates to confirm that Corynebacterium diphtheriae was the agent that caused diphtheria.​
• Helicobacter pylori :


  Infection with the bacteria Helicobacter pylori is the cause of most stomach ulcers. The discovery is generally credited to Australian gastroenterologists Dr. Barry Marshall and Dr. J Robin Warren, who published their findings in 1983. ​
• Dr. Barry James Marshall- received Nobel Prize Laureate in Physiology or Medicine
• Karl Landsteiner and Erwin Popper:

  announced that the infectious agent in polio was a virus.​
• Thomas Peebles Isolates the Measles Virus​:

  Thomas Peebles, MD, working in a laboratory at Boston Children’s Hospital, was asked by lab director John Enders to isolate the virus responsible for measles
• Immunodeficiency virus:

  • The discovery of the virus took several years of research. It was announced in 1984 by Dr. Gallo of the National Cancer Institute, Dr. Luc Montagnier at the Pasteur Institute in Paris, and Dr. Jay Levy at the University of California, San Francisco.​
  • AIDS was first reported June 5, 1981​
• Shapes of Bacteria​:

  • Bacillus (rod)​
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  • Coccus (sphere)​

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  • Spirillum (spiral)​
• Arrangements of Bacteria

  Straight chains of bacteria are referred to as: strepto-
• Arrangements of Bacteria​:

  • Two cells of bacteria are called - diplo-​
• Arrangements of Bacteria:

  • A cluster of bacterial cells is known as - staphylo-​
• Gram Stain:

  • Developed by the Danish bacteriologist Hans Christian Gram in 1884​

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  • Classifies bacteria into two major groups:​
  • Gram-positive​
  • Gram-negative​
• Gram positive bacteria -

  • cell walls composed mostly of a substance unique to bacteria known as peptidoglycan, or murein. ​
  •  These bacteria stain purple after Gram staining.​
  • Examples of Gram positive cocci that colonize the skin include Staphylococcus epidermidis, Staphylococcus aureus, and Streptococcus pyogenes.​
• Gram-negative bacteria: resistant against antibodies because of their impenetrable cell wall.​

  • Gram negative bacterial cell wall is composed of peptidoglycan.​
  • Gram negative bacteria stain pink when subjected to a Gram stain procedure​
  • Gram negative bacteria ​

     produce endotoxins.​
• Gram Negative Spiral Bacteria:

  • Slender and flexible, come in a lot of different shapes​

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  • More rigid than spirochetes​

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  • Ex. – Campylobacter jejuni​

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  • Symptom – tenesmus: the sensation of desire to defecate, which is common and occurs frequently , with out the production of significant amounts of feces (often small amounts of mucous or blood are alone passed).​