Staph

• Most important, and most commonly encountered organism in medical practice.

  • Ubiquitous Human Parasite

  Staphylococcus
• Staphylococcus Colonize 30%- 50% of the skin and mucous membranes of Healthy adult and Children
• Chief source of infection of Staphylococcus are 1.shedding from human lesions2.fomites3.contaminated lesion esp. respiratory tract and skin4.asymptomatic carriers among hospital staff & patient
• •used to distinguish among Gram-positive cocci


  Catalase Test
• Bacteria + 3% Hydrogen Peroxide --> Water and Oxygen


  Catalase Test
• •used to distinguish between pathogenic and nonpathogenic members of the genus Staphylococcus


  Coagulase Test
• •enzymes that clot blood by a mechanism that is similar to normal clotting

  Coagulase Test
• All pathogenic strains of S. aureus are?

  Coagulase Positive
• All non-pathogenic strains of S. aureus are?

  Coagulase Negative
• Coagulase-negative of Staphylococci?

  Staphylococcus epidermidis
• 2 types of coagulase test

  1. bound coagulase
  2. free Coagulase
• known as clumping factor

  Bound coagulase- Slide test
• •cross-links of fibrinogen in plasma to form fibrin clot that deposits on the cell wall•individual coccus stick to each other and clumping is observed


  bound coagulase
• agent for bound coagulase is?

  Citrated Plasma
• is an extracellular enzyme

  Free coagulase
• •free coagulase secreted by S.aureus reacts with coagulase reacting factor (CRF) in plasma to form thrombin; converts fibrinogen to fibrin resulting in clotting of plasma
• •Endotoxins are lipopolysaccharides (LPS) and is secreted by Gram-negative bacteria
• •Exotoxins are peptides that are mostly secreted by Gram-positive bacteria.
• Staphylococcus aureus

  ••most pathogenic •resp for 80% of suppurative infection in human •important pathogen for hospital & community acquired infection •capacity to produce disease not diminished even with introduction of antibiotics •dominant site of colonization:  anterior nares, axilla, perineum and 10-15% human skin••

  Morphology:

  •gram + cocci•arranged in grape-like clusters• nonmotile, noncapsulated (mutant strain have capsule & more pathogenic)

  •produce lipochrome ® golden yellow colonies on blood agar
• S. aureus proteins that disables host immune defense

  Protein A

  Coagulase

  Penicillinase

  Penicillin binding protein
• major protein component of cell wall

  protect organism from opsonization and phagocytosis

  major antigenic determinant unique to S. aureus

  Protein A
• •lead to fibrin formation around bacteria, protecting it from phagocytosis

  Coagulase
• • secreted form of beta lactamase
  • disrupts the beta-lactam portion of penicillin molecule, thereby inactivating the antibiotic

  Penicillinase
• also called transpeptidase

  necessary for cell wall peptidoglycan formation and is inhibited by penicillin

  Penicillin-binding protein
• Proteins of S. aureus that tunnels through host tissue

  1. Hyaluronidase
  2. Staphylokinase
  3. Lipase
  4. Protease
• •protein that breaks down proteoglycans in connective tissue


  Hyaluronidase
• •protein that lyses formed fibrin clots


  Staphylokinase
• •destroys tissue proteins


  Protease
• •enzyme which degrades fats and oils that often accumulate on the surface of our body•This degradation facilitates Staphylococcus aureus' colonization of sebaceous glands

  Lipase
• S. aureus exotoxins

  • Cytolytic toxins
  • Exfoliatin
  • Enterotoxins
  • Toxic Shock syndrome toxin(TSST-1)
• types of Cytolytic toxins...

  Hemolysin

  Leucocidin
• Types of hemolysin

  Alpha

  Beta

  Gamma
• Complete hemolysis

  Beta
• Incomplete Hemolysis

  Alpha
• No hemolysis

  Gamma
• an anti-phagocytic cytolytic toxin that damages the cell membrane of Neutrophils and Macrophages causing them to lyses. Helps in the destruction of phagocytic line of the host

  Leucocidin
• an exotoxin that causes skin to slough off(Scalded skin syndrome)

  Exfolliatin
• an exotoxin fo S. aureas that causes food poisoning resulting to vomiting and diarrhea

  Enterotoxins(heat stable)
• An exotoxin of the S. aureus that has a pyrogenic toxin called superantigen that bind to antigen presenting cells (such as macrophages) causing a massive T cell response and outpouring of cytokines, resulting in the toxic shock syndrome


  Toxic Shock Syndrome Toxin(TSST-1)
• Disease for direct organ invasion of S. aureus

  1. Pneumonia
  2. Meningitis
  3. Osteomyelitis
  4. Acute bacterial endocarditis
  5. Septic Arthritis
  6. Skin infection
  7. Bacteremia
  8. UTI