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12 Cards in this Set

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Colonization vs Infection
Colonization: presence of organism; does not cause cell damage or disease unless enters previously sterile site
Infection: replication of organism leads to cell damage
Strict Pathogen vs Opportunist
1. Strict Pathogen always associated with disease
Few examples of organisms that always cause disease
2. Opportunist causes disease in compromised host
Most pathogens can be considered somewhat opportunistic
Term reserved more commonly for organisms that cause disease in markedly compromised hosts
define and give ex. of Virulence Factors
Structures or products that enable bacteria to cause disease.
Genes for virulence factors may be grouped on DNA in Pathogenicity Islands
-Virulence factors include:
Capsules,Fimbriae,Degradativeenzymes, toxins,etc
six ways bacterial entry into body
1. ingestion
2. inhalation
3. trauma
4. needle stick
5. arthropod bite
6. sexual contact
six ways bacterial exit from the body
1. respiratory secretions
2. feces
3. blood
4. exudates
5. urine
6. sexual secretions
Pathologic Effects of Excess Endotoxin
Fever
Leukocytosis
Complement activation
DIC
Thrombocytopenia
Decreased organ perfusion
Shock
Multi-organ dysfunction syndrome
Death
differentiate exotocin from endotoxin
1. endotoxin
Found in Gram negative cell walls
Released from dying bacteria cells
Locally small amounts can stimulate immune responses
Large amounts in blood associated with septic shock
2. exotoxin
Secreted proteins
Most bind to receptors on host cells
2 subunits
A (activity)
B (binds to cell)
Kill or alter function of host cell
Genes for toxins often encoded on plasmids or lysogenic phage
E.coli in UTI's has what specific virulence factors associated with it?
1.Adhesins
Pili attach to uroepithelial cells
Urine flow does not remove adhered bacteria
2.Endotoxin (LPS)
Stimulates innate immune response
Neutrophils enter site
Pyuria (pus in urine)
3.Capsule
Inhibits phagocytosis
4.Hemolysins
Lyse RBCs releasing iron necessary for bacterial growth
Lyse cells, enabling invasion
5.Antibiotic resistance
Streptococcal Virulence Factors Involved in Cellulitis
Virulence Factors Promote:
Adhesion
Colonization
Invasion
Evasion of Host Defenses
Disease Production
Streptococcal Virulence Factors Involved in Adherence and Colonization
Bacteria enter epidermis following skin trauma (minor, undetectable)
At least 10 structures are involved in adhesion and colonization including:
1.Lipoteichoic acid
Initial interaction with skin via binding to fibronectin
2.F proteins
Also binds fibronectin
Promotes internalization within host cells
3.M proteins
Promote microcolony formation
Promotes internalization within host cells
Virulence Factors Involved in Invasion and/or Cell Death
Hyaluronidase
Breaks down hyaluronic acid (part of connective tissue)
Streptokinase
Lyses clots- facilitates spread
Streptolysins
Lyse cells
Pyrogenic exotoxins
Superantigens
Virulence Factors Associated with Evasion of Host Defenses
Antiphagocytic substances
Capsule
M protein
Inhibition of Complement
M protein inhibits activation by alternative pathway
C5a peptidase breaks down C5a, an attractant of neutrophils
Degradation of Immune Globulins
Several proteases