(04) Microbial Pathogenesis Flashcards
Define Pathogen
A microbe capable of causing disease especially in immunocompetent people
Pathogenesis
The mechanism of disease developement
Virulence
a measure of a microbe’s ability to cause disease
Virulence Factor
any number of products produced by pathogens that allow the microbe to invade, evade host defenses, and/or cause disease
**Differentiate colonization from infection
Colonization - Presence and multipication of microorganisms WITHOUT tissue invasion or damage
Infection - colonization that leads to disease
Define Epidemic
a disease that rapidly affects many people in a fixed period of time
Define Pandemic
a disease that affects people worldwide
Define Endemic
Disease that is constantly present at low levels in a specific population
What are Primary Pathogens?
- synonymous term?
Pathogens that are ALWAYS associated with disease
Synonym = Frank Pathogens
What are Opportunistic pathogens?
- virulence?
Pathogens that are ONLY a problem for immunodeficient people
- Typically lower virulence
In terms of Primary Pathogens and Opportunistic Pathogens, where do most pathogens fall?
- Somewhere in between
- *What are the 4 determinants for infection?
- Where applicable indicate if these pertain to innate or adaptive immune system
- Number of Microorganisms
- Depends on your exposure - Virulence of Microbe
- fewer needed for disease if they’re extremely virulent - Host immune status
- INNATE response - Past immune history
- ACQUIRED response
What are the stages of bacterial pathogenesis?
- Transmission
- Evasion of Host Defenses
- Adherence
- Colonization
- Spread
- Symptoms produced by toxin production or invasion and inflammation
- Host Response
- Progression or Resolution
What is the incubation period?
- what 5 stages or pathogenesis are within the incubation period?
Incubation Period - time period before symptoms are expressed
5 steps during Incubation:
- Transmission
- Evasion of Defenses
- Adherence
- Colonization
- Spread
What are the 2 general type of symptoms a patient may experience?
- Prodomal (non-specific)
2. Specific
What are the most common routes of infection?
- Respiratory
- GI (Fecal-oral)
- Blood-Borne
- Sexual
- Maternal-Fetal or Neonatal
- Vector- or animal-borne
- Fomites, Soil, Water
Respiratory
- most common infection type
- ability to control
- Viral Infection = most common
- Hard to control airborne pathogens
GI (fecal oral)
- ability to control
Well controlled in 1st world countries
Blood-Borne
- how do these infections typically arise
- IV drug use and Transfusions
Maternal-Fetal or Neonatal Infections
- occur where?
- Infections occuring in utero or perinatal (at the time of delivery)
Vectorborne/animal borne illnesses
- how are they contracted?
- Which is most common?
- Eradication?
- Contracted via Direct Animal Contact
- MORE OFTEN contracted from arthropod like a mosquito or tick
- These types of pathogens are hard to irradicate
What are the 3 most common portals of entry?
- what do these have in common
- Respiratory Tract
- GI tract
- GU tract
**These are areas where the skin and mucous membranes meet
What are some of the defenses of the Respiratory Tract?
- Nasal Turbinates, oropharynx, larynx
- Ciliary Epithelia of Lower resp. tract
- Mucus, sIgA, Lysozyme, Lactoferrin
- Alveolar Macrophages
- Upper respiratory tract normal flora
What are some of the defenses of the GI tract?
- Stomach acid, Bile
- Peristalsis
- GALT
- Lysozyme, sIgA, Mucus, Lactoferrin
- Normal LOWER GI flora
What are some of the defenses of the Genital tract?
- Low pH
- Mucus, sIgA, Lysozyme, lactoferrin
- Normal Flora
What are some defenses of the Urinary tract?
- Mechanical Flushing
- sIgA
- Low pH
What mechanism (virulence factor) counters mechanical flushing in the Urinary Tract?
- Ability to Adhere (through pili, etc)
Obligate Intracellular Pathogens
- problem with isolating?
They usually cannot be cultured for a clinical Dx
What are facultative Intracellular Pathogens?
- Grow on Medium but KEY ASPECT of pathogenesis is Hi-jacking a cell
**Hiding in macrophages etc.
what does the Type III secretion system have to do with Receptor mediated endocytosis?
- Bacteria that want to become intracellular may inject its own receptor into the host cell so that it can bind and enter the cell
Transcytosis
- what is it?
- e.g. of what does it?
- Bacteria moves through a cell to enter a new space
- Shigella can travel from gut lumen through M Cell into subepithelial space
3 common ways to prevent receptor mediated endocytosis?
- Prevent Fusion with Phagosome
- Prevent Phagosome fusion with lysosome
- Prevent acidfication by lysosome
What does it mean if an infection disseminates?
- how can it do this?
- what is a likely cause of distal disemination?
- Spreads throughout the body
via:
- Blood
- Lymph
- CSF
**Toxin dissemination WITHOUT bacterial spread
What are 5 non-toxin virulence factors associated with spread and survival of pathogens?
- Capsule
- Collagenase and Hyaluronidase
- Coagulase
- IgA protease
- Protein A
Capsule
- virulence action
- how can it be countered
- common bacteria with it?
- Disease associated with these bacteria?
- Antiphagocytic
- Countered by VACCINE-DERIVED antibodies
Commonly in:
- S. pneumoniae
- H. influenzae
- N. Meningitidis
**Commonly associated with meningitidis
Collagenase and Hyaluronidase
- virulence action
- associated bacteria
- Allow permeation through subcutaneous tissue
- Skin associated bacteria (usually staph)
Coagulase
- virulence action
- associated bacteria
- Causes blood clot which prevents macrophages from accessing pathogen
- Staph aureus
IgA Protease
- most active where?
- Cleaves where?
- associated bacteria
- Most active on MUCOUS surfaces because its IgA
- Cleaves at the Hinge Region
Associated Bacteria:
- S. pneumoniae
- H. influenzae
- N. gonorrheae
Protein A
- Virulence Action
- Associated Bacteria
- Binds to IgG Fc thus preventing the action of the complement
- Staph Aureus associated
What are the 2 types of inflammation?
- associated cells?
- Pyogenic (pus-producing) - Neutrophils
2. Granulomatous - Macrophage
Where do most of our symptoms that arise from viruses come from?
- Our own immune response
- *What are the 3 hallmarks of sepsis?
- what causes sepsis?
- Low Blood Pressure
- Fever
- Coagulation
- Caused by LPS (gram -) or Lipoteichoic acid (gram +)
Exotoxins
- made of?
- Beneficial Uses?
- Peptides
- Antigenic so inactivated forms (toxoids) can be used for immunization by inducing antibodies
What are 4 types of Exotoxins?
- A-B Exotoxins
- Metalloproteases
- Pore-forming toxins
- Superantigens
A-B Exotoxins
- composition
- how do they work?
- examples?
Composition:
- A subunit - active toxic subunit
- B subunits - Binds the toxin to the target
How: 1. ADP-ribosylation of G proteins (most common) 2. Alter ribosomes 3. Inhibit protein synthesis
examples:
- Diphtheria Toxin
- Cholera Toxin
Metalloproteases
- how do they work?
- Examples
- Cleave snares blocking neurotransmitter delivery
Examples:
- botulism - flaccid
- tetanus - rigor
Superantigens
- how do they work?
- associated bacteria?
- Bind to MHC II on APCs results in cytokine storm by T-cells
Bacteria:
- Staph aureus
- Group A Streptococci
T or F: many resolved infections lead to life-long immunity
True
What are 3 general types of unresolved infections?
- Recurrent Infections
- Persistent Infections
- Cancer
What are 3 reasons why a patient would have recurrent infections?
- Poor Immune Response (incomplete irradication)
- Antigenic Variation (gonorrhea - pili)
- Many serotypes
What are 2 reasons for persistent infections?
aka ones that go away and come back
- Chronic Infections
2. Latent Infections (e.g. herpes)
What are some cancer causing bacteria and viruses?
Bacteria:
- H pylori
Viruses:
- HPV, HBV, HCV, EBV, KSHV, HTLV-1
