unit 4 part 1

• Direct damage to cells/tissue

  • Toxins (usually protein molecule that causes damage)
  • Bacteria
  • Enzymes (interferes with metabolic processes/damage body)
  • Metabolic Products/Wastes (causes damage)
• Intracellular infection


  • Bacteria and viruses
• Host Immune Response


  • B/T cell activity
  • Complement
  • Interferon
• Interferon released to nearby cells will cause shutdown of their own metabolic activities
• Inflammation


  • Cells, proteins, fluids that rush to particular area (too much)
• Prions


  Infectious proteins, alternate versions of normal proteins found in cells, some changes in amino acids
• Mechanism of action of prions


  1. Insert themselves into cell membranes

  2. Cause normal proteins to fold

  3. Enough folding causes membrane to lose structure (cell membranes fall apart leading to big holes)
• Fungal Pathogenesis


  • Toxin production
  • Tissue Degradation
• Toxin production

  Generally produced outside the body and enter the body via something that is ingested (I.E. ergot of rye)
• Tissue Degradation


  Degrade (dissolve) our tissue with enzymes
• Allergic Reactions


  • Hyperactive immune system response
• Parasite Pathogenesis


  • Cell/Tissue damage
  • Physical damage (hooks/barbs/suckers)
  • Nutrient Deficiencies
• Nutrient Deficiencies


  Deprivation of host, especially harmful to children in developing countries
• Avoiding/Altering Host defenses


  • Disruption
  • Evasion
  • Inactivation/Suppression
• ALL 3: skilled at hiding by switching antigens on surfaces, coating themselves in body cells, making enzymes that stop antibodies
• Diagnosing Diseases - Methods


  • Phenotypic method
  • Genotypic method
  • Immunologic
• Phenotypic method


  Focusing on physical characteristics, how much peptidoglycan, flagella, cell wall, etc.
• Genotypic method


  Sequencing DNA/RNA
• Immunologic


  Based on antibody/antigen interactions
• Phenotypic Methods


  1. Culturing and biochemical testing

  2. Staining

  3. Shape/arrangement

  4. Direct antigen testing
• Genotypic Method


  1. Polymerase chain reaction (PCR)

  2. Fluorescent In-Situ Hybridization (FISH)
• Immunological Methods


  1. Agglutination

  2. Precipitation

  3. Enzyme-Linked Immunoassay (ELISA)
• Staphylococci Sp.


  • Gram positive cocci
  • Irregular clusters
• Distribution of Staphylococci Sp.

  • Skin, mucous membranes of animals
  • Free-living in environment
• Major Species of Staphylococci


  • S. aureus
  • S. Epidermidis
  • S. Capitis
  • S. Hominis
  • S. Saprophyticus
• About 100,000 deaths annually in the US from Staphylococci Sp. infections, dangerous considering modern day of antibiotics
• S. Aureus


  • Metabolically diverse
  • Can tolerate many different environments (salt, acid, lack of oxygen, etc.)
  • Enzymes (Coagulase, Staphylokinase, Penicillinase)
  • Exotoxins (Leukocidin, Exfoliative toxin, Toxic shock toxin, Alpha toxin)
• Infections caused by S. Aureus


  • Cutaneous (skin)
  • Systemic (spread through the body)
  • Toxigenic (just toxins are causing a problem)
• Transmission of S. Aureus


  • Endogenous infections (our own bacteria makes us sick)
  • Skin to skin
  • Through food
• Prevention of S. Aureus infections


  • Hand washing
  • Proper disposal of contaminated materials
  • Limit exposure by carriers
• Streptococci Sp.


  • Gram positive cocci
  • Chains
• Distribution of Streptococci Sp.

  • Skin, mucous membranes of animals
  • Free-living
• Major species of Streptococci

  • S. Pyogenes
  • S. agalactiae
  • S. pneumoniae
• Strep. Pyogenes


  • Sticky Capsule
  • Fimbriae
  • Surface antigens (C carbohydrates, M proteins, Lipoteichoic acid)
  • Enzymes (Protease, Streptokinase)
  • Toxins (Streptolysins, pyrogenic/erythrogenic)
• Infections caused by Strep. Pyogenes

  • Skin/local (Impetigo, Streptococcal pharyngitis)
  • Systemic (Scarlet fever, Streptococcal toxic shock syndrome)
• Transmission of Strep. Pyogenes

  • Direct contact (most common)
  • Droplets
  • Fomites
• Prevention of Strep. Pyogenes infections

  • Prevent droplet spread
  • Handwashing
  • Limit contact with carriers
• Neisseria Sp.


  • N. Gonorrhea: Gram negative diplococci
  • N. Meningitidis: Gram negative diplococci
• Distribution of Neisseria Sp.


  • N. Gonorrhea: human urogenital tract
  • N. Meningitidis: Human respiratory tract
• Virulence Factors of Neisseria Sp.

  • Fimbriae
  • Protease (breaks apart antibodies)
  • Capsules (N. Meningitidis)
  • LPS (lipopolysaccharide, endotoxin) (N. Meningitidis)