L4

• Important Properties of Staphylococci:

  1. Spherical cocci in clusters

  2. Catalase and coagulase positive
• Classification according to Pigment Formation:

  1. Staphylococcus aureus – golden pigment

  2. Staphylococcus citreus – yellow pigment

  3. Staphylococcus albus – white pigment
• Classification according to Hemolysis:

  1. Alpha hemolysis – incomplete hemolysis

  2. Beta hemolysis – complete hemolysis

  3. Gamma hemolysis – absence of hemolysis.
• Diseases of Staphylococci:

  1. Boils, abscess, carbuncles, faruncles
  2. 2. Septicimia, bacteremia, pyemia
  3. 3. Peritonitis, meningitis, osteomyelitis, endocarditis
  4. 4. Food poisoning
  5. 5. Toxic Shock Syndrome (TSS)
• Staphylococci cause disease by: 1. Producing toxins

  2. Multiplying in tissue
• Important toxins and enzymes produced

  1. Entero toxin – causes vomiting and diarrhea

  2. Exfoliatin – causes scalded – skin syndrome

  3. Leukocidins, hemolysins

  4. TSST
• Habitat and transmission of Staphylococci:

  Habitat is the human skin and nose

  • Transmission is via the hands.
• Important Properties of Stretococcus:

  1. spherical cocci arranged in chains.

  2. catalase negative
• Streptococcus pneumoniae (pneumococci) – bile soluble
• Viridans streptococci- e.g. Strep. Mitis, Strep. mutans
• Alpha Hemolytic

  1. Streptococcus pneumoniae (pneumococci)

  2. Viridans streptococci
• Group A – Streptococeus pyogenes – most important human pathogen
• Group B Streptococci - normal inhabitants of female genital tract

  • cause neonatal meningitis and sepsis
• Group D streptococci include:

  a)Enterococci

  b) Non – enterococci
• Enterococci - Strep. Fecalis inhibited but not killed by penicillin normal flora in the GUT

  • cause urinary, cardiovascular infection
• b) Non – enterococci - Strep. Bovis

  • readily killed by penicillin and inhibited by 6.5% NaCl.
• Group C streptococci – infrequently cause human disease.
• Peptostreptococci

  • anaerobic or microaerophilic streptococci
  • produce variable hemolysis
  • normal flora of the GUT and female genital tract
  • participate in mixed infections in the abdomen, lung, or brain
• Streptococcus pyogenes produce diseases like:

  • erysipelas
  • pharyngitis
  • cellulitis
  • scarlet fever
  • puerperal fever
  • rheumatic fever
  • acute glomerulonephritis
  • streptococcal pyoderma
  • infective endorcarditis
• Streptococci produce the following toxins and enzymes:

  1. Streptokinase

  2. Streptodornase

  3. Hyluronidase

  4. Erythrogenic toxin

  5. Hemolysin

  6. Leukocidin
• Streptokinase – activates plasmin in blood.
• Streptodornase – liquefies thick purulent exudates due to the breakdown of DNA
• Hyluronidase – hydrolyzes ground substance of connective tissue
• Erythrogenic toxin – thermostable exotoxin associated with scarlet fever (red skin rash)
• Hemolysin – produces hemolysis of RBC also known as streptolysin
• Leukocidin – destroys WBC
• Habitat and Transmission of Streptococci:

  • habitat is the human throat and skin
  • transmission is via respiratory droplets
• Streptococci (Viridans group)

  • Strep. sangus and Strep. mutans
• Important properties of Viridans group:

  1. gram positive cocci in chains

  2. alpha hemolytic

  3. catalase negative
• Disease of Viridans:

  • Endocarditis
• Pathogenesis of Viridans:

  • bacteremia from dental procedures spreads organisms to damaged heart values.
• Habitat and transmission of Viridans:

  • habitat is the human oropharynx
  • enter the blood stream during dental procedures
• Important Properties of PNEUMOCOCCUS (Streptococcus Pneumoniae):

  1. gram positive, lancet shaped cocci in pairs

  2. alpha hemolytic

  3. Catalase negative

  4. Cannot be phagocytized (with poly saccharide capsule)
• Diseases of PNEUMOCOCCUS (Streptococcus Pneumoniae):

  1. pneumonia and meningitis in adults

  2. otitis media and sinusitis in children
• Pathogenesis of PNEUMOCOCCUS (Streptococcus Pneumoniae):

  • includes inflammatory response
  • no known exotoxins
  • capsule retards phagocytosis
• Habitat and transmission:

  • habitat is the human upper respiratory tract
  • transmission is via respiratory droplets
• Important Properties of Neisseria Gonorrhea (Gonococcus):

  1. gram negative “ kidney – bean” diplococci

  2. oxidase positive

  3. Insignificant capsule
• Important Properties of NEISSERIA MENINGITIDIS (Meningococcus)

  1. gram negative “kidney – bean” diplococci

  2. oxidase positive

  3. large polysaccharide capsule
• Diseases of NEISSERIA MENINGITIDIS (Meningococcus)

  • Meningitis and meningococcemia
• Pathogenesis of NEISSERIA MENINGITIDIS (Meningococcus)

  • after colonizing the upper respiratory tract, the organism reaches the meninges via the blood stream.
  • endotoxin causes septic shock in meningococcemia