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3.30 Mon Lectures The pyogenic cocci (1)
4.1 Wed Lectures The pyogenic cocci (2)
4.6 Mon Lectures Enterobacteriaceae,Vibrios,Mycobacteria helicobacter pylori,Corynebacterium (1)
4.6 Mon Lab Care and use of the microscope
4.8 Wed Lectures Enterobacteriaceae,Vibrios,Mycobacteria helicobacter pylori,Corynebacterium (2)
4.9 Thur Lab Care and use of the microscope
3.30 Mon Lectures The pyogenic cocci
4.1 Wed Lectures Enterobacteriaceae,Vibrios,Mycobacteria helicobacter pylori,Corynebacterium (1)
4.6 Mon
4.6 Mon Lab Care and use of the microscope
4.8 Wed Lectures Enterobacteriaceae,Vibrios,Mycobacteria helicobacter pylori,Corynebacterium (2)
4.9 Thur Lab Care and use of the microscope
The labs in the next week are canceled, will be
shifted to the following week. Labs will extend
to 5.25 and 5.28.
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Coccus

• Zooming in pyogenic coccus
• disease and pathogenesis

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Pyogenic coccus
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Pyogenic coccus
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Major pathogenic species

• Staphylococcus (the staphylococcus)
• Staphylococcus aureus
• Staphylococcus epidermidis
• Staphylococcus saprophyticus
• Streptococcus (the streptococcus)
• Streptococcus pyogenes
• Streptococcus pneumoniae (the pneumococcus)
• Neisseria (the neisseria)
• Neisseria meningitidis (the meningococcus)
• Neisseria gonorrhoeae (the gonococcus)

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Staphylococcus aureus

• Diseases
• Pathogenesis
• Roles of bacterial virulent factors
• Diagnosis
• Methods for bacteria classification
• Treatment and prevention
• Issues

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Bacteria morphology

• Staphylococcus grape-like irregular clusters
• Streptococcus chains or pairs
• Neisseria kidney-shaped diplococci

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Bacteria culture pigmentation

• The bacteria produces liposoluble pigments which
  make the colonies appear in certain color
• Staphylococcus aureus
• golden yellow
• Staphylococcus epidermidis
• white
• Staphylococcus saprophyticus
• white or lemon yellow

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Bacteria culture mannitol fermentation

• Biochemical reactions for example,
  Staphylococcus aureus is capable of using sugar
  mannitol (???) as a food source and will produce
  acidic byproducts of fermentation that will lower
  the pH of the media.

Staphylococcus aureus, Staphylococcus
epidermidis, Streptococcus pneumoniae and
Streptococcus pyogenes on mannitol salt agar
plates (containing 7.5 NaCl, mannitol and phenol
red).
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Diseases
I. Suppurative infections (?????) II.
Toxicoses (?????)
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I. Suppurative infections

• Local infections (contained at the local)
• Superficial skin lesions such as sore (?),
  furuncle (?) and stye (???,???)
• Systemic infections (spread through the blood
  stream)
• Septicemia (???)
• Pyemia (???) spread to different organs to cause
  pneumonia (??), mastitis (???), phlebitis (???),
  meningitis (???), urethritis (???) and abscesses
  (??)

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II. Toxicoses

• Food poisoning
• A gastrointestinal illness. Symptoms include
  nausea, vomiting, stomach cramps, and diarrhea.
• Toxic shock syndrome (TSS,???????)
• Characterized by a sudden onset of fever, chills,
  vomiting, diarrhea, muscle aches and rash. It can
  rapidly progress to severe and intractable
  hypotension and multisystem dysfunction. Commonly
  occurs in women.
• Scalded skin syndrome (SSS, ????????)
• Caused by staphylococcal skin infection. The skin
  blisters and peels off as though burned.
  Additional symptoms are fever, chills, and
  weakness. commonly occurs in infants.

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Pathogenesis

• Cell wall virulent factors
• Staphylococcal protein A (SPA)
• Coagulase
• Exotoxins
• Staphylolysin (cytolytic)
• Leukocidin (cytolytic)
• enterotoxin (superantigen)
• toxic shock syndrome toxin 1 (superantigen)
• Exfoliatin (superantigen)

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Staphylococcal protein A (SPA)

• Surface bound (in the cell wall) or free
  proteins.
• Bind to Fc portion of IgG from human, mouse and
  guinea pig (but not to that from rabbit), and
  thus inhibit Fc receptor-mediated phagocytosis by
  macrophages.

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Inhibition of phagocytosis
Fc receptor
SPA
IgG
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Agglutination test

• In this test, anti-Staphylococcus aureus IgG can
  bind SPA using Fc fragment and the bacteria
  through Fab to from complexes that can been seen
  with eyes.

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Coagulase

• Bound (in the cell wall) catalyzes fibrinogen
  (?????) into fibrin (????). Cause coating of the
  bacteria with fibrin and thus inhibit
  phagocytosis and killing mediated by serum
  components.
• Free secreted and turns into staphylothrombin
  after activation by cofactors in the plasma,
  which catalyzes fibrinogen into fibrin. Cause
  coagulation of the plasma and helps to restrain
  infections at the local.

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Coagulase test and CNS

• A test of coagulation of human or rabbit plasma
  in the presence of anticoagulant (citrate or
  heparin).
• Coagulase-negative staphylococci (CNS) used to be
  thought as non-pathogenic, however, they have
  become a major source of hospital-acquired
  infections
• Staphylococcus epidermidis
• Staphylococcus saprophyticus

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Cytolytic exotoxins staphylolysin and leukocidin

• Attack mammalian cell membranes, cause abscess
  and tissue necrosis. Often referred to as
  hemolysins.
• Staphylolysins
• Four types ?, ?, ? and ?
• Staphylolysin ?, ? and ? can lyse erythrocytes
  (the basis for hemolytic reaction) toxic to many
  other cells such as white blood cells and muscle
  cells
• Staphylolysin ? close to leukocidin.
• Leukocidin lyse macrophages and neutrophils.

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Hemolysis test
Bacteria are grown on sheep blood agar plates
(containing 5 sheep blood)
a- hemolytic reaction, partial hemolysis with a
green coloration
Streptococcus pneumoniae
ß- hemolytic reaction, complete hemolysis
Staphylococcus aureus Streptococcus pyogenes
? - hemolytic reaction, no hemolysis
Staphylococcus epidermidis most strains
Staphylococcus saprophyticus
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Superantigens

• Superantigens can bind both to class II MHC
  molecules (but not in the peptide cleft) and also
  to a relatively conserved region of the TCR
  ßchain.
• This leads to non-specific activation of 2-20 of
  all T cells (vs. 0.01), and massive unregulated
  cytokine release.

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Superantigen exotoxins enterotoxin, TSST-1 ,
and exfoliatin

• Enterotoxin, 9 serotypes, responsible for
  staphylococcal food poisoning.
• TSST-1, close to enterotoxin, cause toxic shock
  syndrome (TSS).
• Exfoliatin, 2 serotypes, cause staphylococcal
  scalded skin syndrome (SSS).

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Diagnosis

• Pus
• abscesses and superficial skin lesions
• Sputum
• lower respiratory tract infections
• Blood
• septicemia, pyemia
• Food/feces or vomit
• food poisoning
• Mid-stream urine
• urethritis

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S. aureus CNS Streptococcus Neisseria
Gram staining -
bacteria morphology irregular clusters irregular clusters Chains or pairs Kidney-shaped diplococci
colony pigmentation Golden white
mannitol fermentation -
hemolysis test ß-hemolytic ? -hemolytic
coagulase test positive negative
agglutination test Use serum samples from patients. Use serum samples from patients. Use serum samples from patients. Use serum samples from patients.
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Treatment and prevention

• Antibiotics
• MRSA refers to methicillin (??????)-resistant
  Staphylococcus aureus, and most MRSA strains are
  also multiple drug resistant
• Chromosomal mutation
• Plasmid-conferred
• CNS, eg. Staphylococcus epidermidis
• Biofilm formation
• Exotoxin neutralizing antibodies
• No vaccines available currently

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Summary

• Major pyogenic cocci
• Identification of Staphylococcus aureus and
  related bacteria (diagnosis)
• Diseases and molecular mechanisms
• Drug resistance and mechanisms