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• 1 Introduction to Bacteriology

• 1.1 Microbiome vs pathogens

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• Microbiome, human-associated microbes

  • 4x10^13 microorganisms
  • 500 - 1000 different spicies 

• What do good bacteria of the microbiome do as a source of health?

  • Nutrition and metabolism of food 
    
  • breakdown of indigestible polysaccharides
  • production of vitamins B and K
  • Maturation and instruction of immune system 
  • Colonization resistance: protection against invaders

• What do bad bacteria of the microbiome do as a source of disease?

  • Potential disease-causing bacteria among healthy microbiome
  • Risk of infection 

• Which are the bad bacteria among the microbiome?

  • Neisseria meningitidis
  • gram-negative diplococcus
  • human is the host
  • causes meningitis/sepsis
  • Streptococcus pneumoniae
  • Staphylococcus aureus
  • Group A Streptococcus

  
  
  
  Neisseria meningitidis and Streptococcus pneumoniae have a similar clinical picture but are different pathogens causing it. 

• What is a carrier?

  Host that harbours potential pathogen without disease

• What are the two different clinical pictures Staphylococcus aureus causes?

  • Scalded skin syndrome
    
  • Exfoliative toxins A and B
  • Toxin binds to a molecule within the desmosome and breaks it up so the skin cells become unstuck
  • Food poisoning
  • Enterotoxin A
  • Toxin is resistant to conditions (heat treatment, low pH) that destroy the bacteria that produce them

  
  
  The different clinical pictures is due to the way of entry of Staphylococcus aureus.
  

  • barrier of skin
  • ingested contaminated food

  
  
  

• 1.2.1 Porte d'entrée: route of contamination and invasion of the host

• What are the porte d'entrée sites?

  • Skin or mucous membranes 
    
  • Wound infections, STD (SSSS: bacteria S. Aureus)
  • Transcutaneous
  • via vectors, insects 
  • Directly in the bloodstream 
  • needle drug user, tooth extraction 
  • Airways
  • upper/lower respiratory tract (SSSS)
  • Gastrointestinal 
  • Contaminated food (good poisoning)

• What are the different types of pathogenicity?

  1. Invasiveness (also called tropism): ability to invade tissues
  • Colonization
  • Bypass host defense
  2. Toxigenesis: ability to produce toxins
  • Exotoxins
  • Endotoxins

• 1.2.2 Properties of microorganism

• What is the course of infection determined by? Which are those?

  Virulence factors
  

  • Adhesins
  • Invasins
  • Capsule
  • Toxins
  • Enzymes
  • Pill
  • enhances bacteria's ability to bind to body tissues, which increases replication rate

• What are the virulence factors of S. Aureus?

  Toxins
  

  • Cytolytic toxins
  • tissue destruction / abscess formation 
  • Entrotoxins (A-E)
  • toxicity
  • Exfoliative toxin
  • blistering: loss of desmosomes

  
  Enzymes 
  

  • Coagulase
  • conversion fibrinogen to fibrine
  • Hyaluronidase, lipase, fibrinolysis
    
  • distribution in tissues
  •  Catalase
  • protection against oxygen radicals