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Chapter 15 Micro mechanisms of pathogenicity

question
Pathogenicity
answer
ability to cause disease
question
Virulence
answer
degree of pathogenicity (damage caused by microbe to host)
question
Portal of entry of pathogens
answer
Correct portal must be used for a specific organism to cause disease
question
3 different portal of entry of pathogen
answer
1. mucous membrane:
-respiratory tract: inhaled through nose or mouth (cold, pneumonia, TB, Flu, measles)
-gastrointestinal tract: food, water, contaminated fingers (hepatitis A, typhoid fever, amebic dysentery)
-genitourinary tract: pathogen contracted sexually (STI's, genital warts, chlamydia, syphilis, gonorrhea)

2. Skin: openings of skin like hair follicle, sweat glands (hookworm and fungi)
- conjunctiva: membrane of eyelid (conjunctivitis, ophthalmia neonatorum)

3. Parenteral route: deposited directly into tissues when barriers are penetrated or injured ( injection, bites, cuts, wounds, surgery)
question
Structures which help pathogens evade (escape) host defenses
answer
1. capsule- formed by glycocalyx that surrounds cell wall and increases virulence of species and capsule resists phagocytosis

2. cell wall components:
-M protein: resists phagocytosis

-Opa protein: allows for attachment to hos
t
-mycolic acid (waxy lipid): resists digestion by phagocytes and bacteria multiplies
question
production of exoenzymes
answer
1. coagulase: coagulate fibrinogen that protect bacterium from phagocytosis

2. Kinase: breakdown fibrin and digest clots formed by body to isolate infection

3. Hyaluronidase: digest hyaluronic acid that hold cells together

4. Collagenase: breaks down collagen in CT of muscles/body organs &tissues

5. IGA proteases: destroy IgA antibodies (defense against adherence of pathogens to mucosal surface)
question
Antigenic variation
answer
Pathogens alter their surface antigens and pathogen is unaffected by antibodies
question
Penetration into host cytoskeleton
answer
Invasins produced by bacteria cause rearrange of actin near the membrane resulting to membrane ruffling: holes are created allowing entry of pathogens
question
In what ways can pathogens make the body sick?
answer
...
question
1. using host nutrients
answer
siderophores: proteins produced by pathogens that snatch iron from host cells
question
2. Direct damage to host cell
answer
Pathogens:
1. disrupts host cell functions
2. uses host cell nutrients
3. produce waste products
4. multiply in host cells and rupture and spread to other tissues
question
3. Production of Toxins
answer
Toxins: poisonous substances produced by micros that cause fever, CV problems, diarrhea, shock
question
What is toxemia?
answer
toxins in the blood
question
What is intoxication?
answer
caused by presence of toxin without microbial growth
question
What is toxigenicity?
answer
ability of a microorganism to produce a toxin
question
What are exotoxins?
answer
metabolically active proteins produced and secreted by bacteria that destroy host cell and inhibit metabolic functions
question
What are endotoxins?
answer
Lipid portion of the LPS ; part of the outer portion of cell wall or Lipid A of most gram negative bacteria that are released when cell is damaged
question
Types of Exotoxins
answer
1. A-B toxins: polypeptides
A part: is the enxyme component
B part: binding component

2. membrane-disrupting toxins: cause lysis of host cells by disrupting their plasma membrane
-Leukocidins: kill phagocytic leukocytes (WBC)
-Hemolysins: kill erythrocytes by forming protein channels
-Streptolysins: type of hemolysins (destroy RBC) produced by Streptococci

3. Superantigens: provoke intense immune system response and toxins stimulate T cells to release cytokines resulting in symptoms like fever, nausea, vomit, shock death (pyrogenic=produce fever)

4. Genotoxins: damage DNA or cause mutation disrupting cell division and causing cancer
question
During which growth phase of bacteria are more exotoxins released?
answer
Growth and metabolism and are secreted by the bacterium following lysis
question
When are endotoxins like Lipid A released from bacteria?
answer
released during bacterial multiplication when gram negative bacteria die
stimulate macrophages to release a lot of cytokines =fever, weakness, generalized aches, shock, death
question
What are the portals of exit of pathogens?
answer
1. Respiratory Tract: coughing & sneezing
pathogens cause: TB, whooping cough, pneumonia, scarlet fever

2. Gastrointestinal tract: feces & saliva
pathogens cause: salmonellosis, cholera, typhoid fever, amebic dysentery

3. Genitourinary: urine secretions from penis or vagina
pathogens cause: STI's

4. Skin: drainage from abscess (cyst) or wounds, yaws, ringworm, herpes , warts, impetigo
Drainage from wounds can spread infection person to person through direct contact or contact through fomites

5. Infected blood: arthropods (animals) bites, needles or syringes
cause: yellow fever, plaque, malaria, AIDS and hep B
question
How does an endotoxin produce fever?
answer
1. a macrophage ingest a gram neg bacterium
2. bacterium is degraded and release endotoxins that tell macrophage tp produce cytokines, interleukin 1, TNF-a
3. cytokines are released into the blood stream and travel to the hypothalamus
4. cytokines make hypo produce prostaglandins=reset the body thermostat to higher temperature=fever
1 of 22
question
Pathogenicity
answer
ability to cause disease
question
Virulence
answer
degree of pathogenicity (damage caused by microbe to host)
question
Portal of entry of pathogens
answer
Correct portal must be used for a specific organism to cause disease
question
3 different portal of entry of pathogen
answer
1. mucous membrane:
-respiratory tract: inhaled through nose or mouth (cold, pneumonia, TB, Flu, measles)
-gastrointestinal tract: food, water, contaminated fingers (hepatitis A, typhoid fever, amebic dysentery)
-genitourinary tract: pathogen contracted sexually (STI's, genital warts, chlamydia, syphilis, gonorrhea)

2. Skin: openings of skin like hair follicle, sweat glands (hookworm and fungi)
- conjunctiva: membrane of eyelid (conjunctivitis, ophthalmia neonatorum)

3. Parenteral route: deposited directly into tissues when barriers are penetrated or injured ( injection, bites, cuts, wounds, surgery)
question
Structures which help pathogens evade (escape) host defenses
answer
1. capsule- formed by glycocalyx that surrounds cell wall and increases virulence of species and capsule resists phagocytosis

2. cell wall components:
-M protein: resists phagocytosis

-Opa protein: allows for attachment to hos
t
-mycolic acid (waxy lipid): resists digestion by phagocytes and bacteria multiplies
question
production of exoenzymes
answer
1. coagulase: coagulate fibrinogen that protect bacterium from phagocytosis

2. Kinase: breakdown fibrin and digest clots formed by body to isolate infection

3. Hyaluronidase: digest hyaluronic acid that hold cells together

4. Collagenase: breaks down collagen in CT of muscles/body organs &tissues

5. IGA proteases: destroy IgA antibodies (defense against adherence of pathogens to mucosal surface)
question
Antigenic variation
answer
Pathogens alter their surface antigens and pathogen is unaffected by antibodies
question
Penetration into host cytoskeleton
answer
Invasins produced by bacteria cause rearrange of actin near the membrane resulting to membrane ruffling: holes are created allowing entry of pathogens
question
In what ways can pathogens make the body sick?
answer
...
question
1. using host nutrients
answer
siderophores: proteins produced by pathogens that snatch iron from host cells
question
2. Direct damage to host cell
answer
Pathogens:
1. disrupts host cell functions
2. uses host cell nutrients
3. produce waste products
4. multiply in host cells and rupture and spread to other tissues
question
3. Production of Toxins
answer
Toxins: poisonous substances produced by micros that cause fever, CV problems, diarrhea, shock
question
What is toxemia?
answer
toxins in the blood
question
What is intoxication?
answer
caused by presence of toxin without microbial growth
question
What is toxigenicity?
answer
ability of a microorganism to produce a toxin
question
What are exotoxins?
answer
metabolically active proteins produced and secreted by bacteria that destroy host cell and inhibit metabolic functions
question
What are endotoxins?
answer
Lipid portion of the LPS ; part of the outer portion of cell wall or Lipid A of most gram negative bacteria that are released when cell is damaged
question
Types of Exotoxins
answer
1. A-B toxins: polypeptides
A part: is the enxyme component
B part: binding component

2. membrane-disrupting toxins: cause lysis of host cells by disrupting their plasma membrane
-Leukocidins: kill phagocytic leukocytes (WBC)
-Hemolysins: kill erythrocytes by forming protein channels
-Streptolysins: type of hemolysins (destroy RBC) produced by Streptococci

3. Superantigens: provoke intense immune system response and toxins stimulate T cells to release cytokines resulting in symptoms like fever, nausea, vomit, shock death (pyrogenic=produce fever)

4. Genotoxins: damage DNA or cause mutation disrupting cell division and causing cancer
question
During which growth phase of bacteria are more exotoxins released?
answer
Growth and metabolism and are secreted by the bacterium following lysis
question
When are endotoxins like Lipid A released from bacteria?
answer
released during bacterial multiplication when gram negative bacteria die
stimulate macrophages to release a lot of cytokines =fever, weakness, generalized aches, shock, death
question
What are the portals of exit of pathogens?
answer
1. Respiratory Tract: coughing & sneezing
pathogens cause: TB, whooping cough, pneumonia, scarlet fever

2. Gastrointestinal tract: feces & saliva
pathogens cause: salmonellosis, cholera, typhoid fever, amebic dysentery

3. Genitourinary: urine secretions from penis or vagina
pathogens cause: STI's

4. Skin: drainage from abscess (cyst) or wounds, yaws, ringworm, herpes , warts, impetigo
Drainage from wounds can spread infection person to person through direct contact or contact through fomites

5. Infected blood: arthropods (animals) bites, needles or syringes
cause: yellow fever, plaque, malaria, AIDS and hep B
question
How does an endotoxin produce fever?
answer
1. a macrophage ingest a gram neg bacterium
2. bacterium is degraded and release endotoxins that tell macrophage tp produce cytokines, interleukin 1, TNF-a
3. cytokines are released into the blood stream and travel to the hypothalamus
4. cytokines make hypo produce prostaglandins=reset the body thermostat to higher temperature=fever
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