Bacterial Virulence Flashcards
What is virulence?
Pathogen/microbe ability to infect
Presentations of Staph aureus?
- Superficial lesions
- Systemic
- Toxinoses (toxic shock, scalded skin sydrome)
Various skin infections of Staph Aureus?
Rash Folliculitis Abscess Carbuncle (multioccular abscesses) Impetigo Scalded skin syndrome
How many broad species are involved in Staphylococci?
Two significant skin colonizing species distinguished as coag +ve/-ve
S. aureus is coagulase?
Positive
S. Epidermis is coagulase?
Negative
When does S. Epidermis tend to cause infection?
Usually only in immunocompromised patients as most people have this pathogen on their skin.
Associated with foreign objects like a catheter
S. Epidermis coagulases plasma. True or False?
False
What percentage of general population carry S. aureus the whole time?
20%
Staph aureus is normally found on?
Nasal passages and perineum
What is MRSA defined by?
Resistance to flucloxacillin
What is toxinoses?
Discrete disease with single protein component, a toxin or exotoxin. (NOT THE ENDOTOXIN)
TSST-1? (toxic shock syndrome 1)
Rapid progression Life threatening High fever Vomiting Diarrhoea Sore throat Muscle pain
Staphylococcal Food poisoning?
Intoxication (not living organism) Self limiting 1-5 hours Vomiting Diarrhoea
Scalded skin syndrome?
Often neonatal Face, axilla & groin Self-limiting Interferes with keratin/cystine cross-bridges causing continual shedding of skin Toxin is a protease
Common cause of toxic shock syndrome?
TSST-1
Mechanism of TSST-1?
Antigen is not processed by PMN binds directly to MHC11 complex.
Massive release of cytokines and inappropriate immune response
Example of a superantigen?
TSST-1
Diagnostic criteria for TSS?
- Fever (39c)
- Diffuse Macular Rash and desquamation (sun burn)
- Hypotension (<90 mmHg)
- 3 or more organ systems involved
Virulence Factor?
Molecules produced by pathogen that add to their effectiveness and enable them to achieve many things
What do virulence factors help pathogens achieve?
- colonization of a niche in the host (this includes attachment to cells)
- immunoevasion
- evasion of the host’s immune response
- immunosuppression
- entry into and exit out of cells (if the pathogen is an intracellular one)
- obtain nutrition from the host
What proteins does Staph.Aureus require to adhere, survive and damage the host?
- Fibrinogen Binding protein (adhesion)
- Haemolysins - Cytolytic
- Coagulase (clots plasma)
- Leucocidin - inactivates leukocytes
- TSST-1
Virulence Factors that are linked to S. Aureus wound infections, necrotising pneumonia & toxic shock?
Protein A
Super antigens (TSST-1)
Gamma toxin, alpha toxin and PVL
Coagulase
Necrotising pneumonia?
- Preceding influenzae like symptoms
- Rapid progression
- Acute respiratory distress
- Deterioration in lung function
- Multi-organ failure
