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

2. Zooming in pyogenic coccus: disease and pathogenesis

3. Pyogenic coccus

4. Pyogenic coccus

5. 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)

6. Staphylococcus aureus
Diseases
Pathogenesis
Roles of bacterial virulent factors
Diagnosis
Methods for bacteria classification
Treatment and prevention
Issues

7. Bacteria morphology Staphylococcus : grape-like irregular clusters
Streptococcus : chains or pairs
Neisseria : kidney-shaped diplococci

8. 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

9. Bacteria culture: mannitol fermentation
Biochemical reactions: for example, Staphylococcus aureus is capable of using sugar mannitol (甘露醇) 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).

10. Diseases
I. Suppurative infections
(化脓性感染)
II. Toxicoses
(毒素性疾病)

11. I. Suppurative infections
Local infections (contained at the local)
Superficial skin lesions such as sore (疮), furuncle (疖) and stye (睑腺炎，麦粒肿)
Systemic infections (spread through the blood stream)
Septicemia (败血症)
Pyemia (脓血症): spread to different organs to cause pneumonia (肺炎), mastitis (乳腺炎), phlebitis (静脉炎), meningitis (脑膜炎), urethritis (尿道炎) and abscesses (脓肿)

13. II. Toxicoses Food poisoning
A gastrointestinal illness. Symptoms include nausea, vomiting, stomach cramps, and diarrhea.
Toxic shock syndrome (TSS,毒性休克综合征)
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, 烫伤样皮肤综合症)
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.

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

16. 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.

17. Inhibition of phagocytosis
Fc receptor
SPA
IgG

18. 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.

19. Coagulase
Bound (in the cell wall): catalyzes fibrinogen (纤维蛋白原) into fibrin (纤维蛋白). 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.

20. 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

21. 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.

22. Hemolysis test
Bacteria are grown on sheep blood agar plates (containing 5% sheep blood):
α- hemolytic reaction,
partial hemolysis with a green coloration：
Streptococcus pneumoniae
β- hemolytic reaction, complete hemolysis：
Staphylococcus aureus
Streptococcus pyogenes
γ - hemolytic reaction, no hemolysis:
Staphylococcus epidermidis most strains Staphylococcus saprophyticus

23. 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 βchain.
This leads to non-specific activation of 2-20% of all T cells (vs. 0.01%), and massive unregulated cytokine release.

24. 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).

25. 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

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

27. Treatment and prevention
Antibiotics
MRSA refers to methicillin (甲氧苯青霉素)-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

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