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IMMUNOLOGY – STAPHLOCOCCI
Gram positive cocci are Staphylococci & Streptococci
Common characteristics → Non-motile
→ Don't from spores
→ Gram positive cocci (it stains purple)
Differential characteristics:
Staphylococci – from grape like clusters & produce catalase (an enzyme that degrade H2O2 into O2 &
H2O
Streptococci – found in chains & do not produce catalase

STAPHYLOCOCCUS
Important properties = Gram positive
Catalase positive
Arranged in irregular grape like clusters

STAPHYLOCOCCUS AUREUS
→ Most common, most serious
...
e
...
g
...

- Toxic shock syndrome
...
This agar also contain a pH sensitive dye
...
Aureus ferments mannitol, the acidic waste product, causes the pH sensitive dye to turn
yellow
...
Aureus)
- NRSA (Nafcillin-Resistant Staph Aureus)
→ MRSA causes both HCA-MRSA (Health-Care Acquired MRSA) and CA-MRSA (Community
Acquired MRSA) infections
...
aureus that
causes leukocyte destruction and tissue necrosis
...

→ It is also an important virulence factor of CA-MRSA
...
aureus
...


TEICHOIC ACIDS:
- Polymers of ribitol phosphate
- Ease the adherence of S
...

- Lipoteichoic acids → induce septic shock
...


Common site for colonization:

→ S
...
of hospital personal & patients)
...
epidermidis;
-

Skin (can enter in bloodstream at the site of I/V catheters)

→ S
...
Aureus:
It is favored by;
-

Heavily contaminated environment (e
...
family members with boils)
Compromised immune system
Diabetes
I/V drug abuse
Chronic Granulomatous Disease

STAPHYLOCOSSUS EPIDEMIDES
→ Coagulase Negative
→ It doesn't synthesize staphyloxanthine thus produce white colonies
→ Sensitive to novobiocin

STAPHYLOCOSSUS SAPROPHYTICUS
→ Coagulase Negative
→ Resistant to Novobiocin

PATHOGENESIS:
Staph
...

- Toxic Shock Syndrome Toxins

- Exofoliatin
ENTEROTOXIN:
- Cause rapid on-set food poisoning, characterized by prominent vomiting and watery, non-bloody
diarrhea
...
2-6 hours
...

- Cause toxic shock, especially in;
-

Tampon - using menstruating women
...

- Epidermolytic, act as protease that clears desmoglein
- Causes separation of the epidermis at the granular cell layer
...
Epidermides & S
...


CLINICAL FINDINGS:
S
...
g
...
Aureus infections

SEPTICEMA (SEPSIS):
- Similar clinical feature → Neisseria meningitidis (Gram Negative Bacteria)
- Originate esp
...
tricuspid valves (right sided endocarditis)

OSTEOMYELITIS & SEPTIC ARTHRITIS:
- Common in children
...
Aureus → most common cause of post-surgical wound infections

PNEUMONIA
- Can occur in post-operative patients or following viral respiratory disease (Influenza)
- Staphylococcal pneumonia → Empyema or lung abscess
→ Most common cause of nosocomial pneumonia or ventilator associated
pneumonia

CA – MRSA → Severe necrotizing pneumonia
...

- transmitted by contaminated fingers
→ S
...

→ Gonococcal & Non-gonococcal conjunctivitis → caused during passage through birth canal
→ caused by Chlamydia trachomatis

ABSCESSES:
If S
...


S
...


STAPHLOCOCCUS EPIDERMIDIS:
-

Hospital acquired
Part of normal human flora of skin & mucous membrane
...
epidermidis

STAPHLOCOCCUS SAPROPHYTICUS:
-

Community acquired
...
Aureus
- Negative → Staph
...
Saprophyticus, Staph
...
Aureus
- Remain White → Staph
...
Epidermidis
- Resistant → S
...
aureus
- Development of antibodies to the toxin during convalescence → Not useful for diagnosis in
acute phases
...

MRSA & NRSA → ß-lactamase - resistant penicillins (nafcillin or cloxacillin)



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