1. The Staphylococci

2. Staphylococci: Gram-positive cocci
staphyle = bunch of grapes Greek

3. The Cell Wall

4. Gram Positive vs. Gram Negative

5. The Gram Stain

6. Medically Important Staphylococci 1. S. aureus-most virulent
pyogenic infections
-abscesses
-endocarditis
-osteomyelitis
-pneumonias
toxin-mediated disease
-food poisoning
-toxic shock syndrome
-scalded skin syndrome
2. S. epidermidis-most abundant
3. S. saprophyticus
-urinary tract infections

9. Abcess (boil)

10. Skin abcesses & boils

11. Scalded Skin Syndrome

14. “opportunistic” members of the normal flora
Staphylococci
“opportunistic” members of the normal flora
S. aureus
nasal carriage in ~30% population,
higher among health care workers.
hardy with flexible nutrition
- survives high temperatures,
resistant to drying, etc.
- widespread in environment
S. epidermidis
skin
S. saprophyticus
urinary tract

15. Features of the pathogenic Staphylococci

16. Bacterial Pathogenesis,
A Molecular Approach
Salyers and Whitt

17. S. aureus factors promote
pyogenic disease
1. Adherence to host extracellular matrix
fibronectin; also collagen, laminin, etc
promotes colonization of deep tissue
2. Inflammation
peptidoglycan and teichoic acid
activate Toll pathway
3. Abscess formation
coagulase - fibrinogen to fibrin clot
contains infection, but limits access

18. S. aureus factors evade clearance
1. Protein A
- blocks opsinization by IgG
2. catalase
- counteracts oxygen free radicals of PMNs
3. b-lactamase
- 90%of strains are resistant to penicillin

19. Staphylococcal Protein A - blocks clearance by macrophages
Fc mediated phagocytosis
by macrophages Fc
Fab A A A

20. S. aureus factors cause damage
1. pyrogenic toxins
- enterotoxins - heat stable; food poisoning
- TSST-1 superantigen; shock
2. a-toxin
- forms pores in RBCs, WBCs, others
3. exfoliatin
- separation of epidermis; ” scalded skin”
4. secreted enzymes
- hemolysins, hyaluronidase, lipase, DNAse, and
proteases that can also activate influenza virus HA

21. Superantigen Mode of Action
TSST-1
hyperstimulates
T cell proliferation
and cytokine release.
Salyers and Whitt,
Bacterial Pathogenesis,
A Molecular Approach

22. Superantigens Exploits normal, regulated, antigen presentation.
Cross-links antigen-presenting cell {APC} to T-cell [MHC to T-cell receptor].
Massive over expression of immune mediators.
Toxic shock.

23. Exfoliative Toxin A cleaves desmoglein,
a cadherin that mediates adhesion in skin tissue

24. Mechanism for horizontal transmission
Exotoxins Encoded by Bacteriophages
staphylococcal enterotoxin A
diphtheria toxin
streptococcal erythrogenic toxins- SpeA, B, C
botulinum toxin types C1 and D
Pseudomonas cytotoxin
Shiga toxins 1 and 2
cholera toxin
Mechanism for horizontal transmission
of virulence genes.

25. Today, an opportunistic infection of traumatic or surgical wounds.
Incidence of Toxic Shock Syndrome
- a disease of technological progress
Rely tampon
taken off market
Today, an opportunistic infection
of traumatic or surgical wounds.

26. Community-acquired MRSA
Healthy school-age children with
no apparent risk factors
have died from
Methicillin-Resistant-Staph aureus.