Micropara 4: Capabilities of Pathogen Flashcards
is the capacity of a pathogen to produce disease
Pathogenicity
seven capabilities of a pathogen
- Maintain a reservoir
- Leave its reservoir and enter a host-transmission
- Adhering to a body surface
- Invade the body
- Evade the body’s defense mechanisms
- Multiply within the body
- Leave the body and return to its reservoir or enter a new host
A place to live before and after infection and is most common
Maintain a reservoir
reservoirs examples
- humans
- animals
- environment (nonliving: soil & water)
examples of human reservoirs
- Diseased
- Carriers
- Virus: smallpox
- Bacterium: gonorrhea, typhoid fever, strep throat
examples of animal reservoirs
- Zoonosis
- Virus
- Bacterium
- Fungus
- Protozoa
a human disease caused by a pathogen with an animal reservoir
Zoonosis
Virus reservoirs
- Rocky Mt. spotted fever
- rabies
- yellow fever
Bacterium reservoirs
- Lyme disease
- plague (Yersinia pestis)
Environmental (non-living) Reservoir examples
Soil, water
Tetanus
Legionnaire’s Disease
Water contaminated with feces
spores live in soil
Tetanus
legionnaire’s disease
water, often in air conditioning ductwork
Water contaminated with feces
- cholera
- typhoid fever
how the pathogen leaves the reservoir and gets to the host
Modes of transmission
Modes of transmission
- respiratory droplets
- fomites (objects)
- Direct contact (touching, kissing, sex)
- Also called person-to-person
- fecal-oral
- Vectors
- Mechanical
- Biological
- airborne
- parenteral (
most common mode of transmission
respiratory droplets
objects mode of transmission
fomites
touching, kissing, sex
Direct contact a.k.a. person-to-person
this mode of transmission examples are ticks, mosquitoes, fleas
Vectors
this mode of transmission can survive drying, ex. TB
airborne
mode of transmission directly into blood
parenteral
the site at which a pathogen enters
Portal of Entry
Portal of Entries of a Pathogen
- Skin
- Mucous membranes of resp tract, GI, and GU
- Respiratory tract (lungs) is easiest
- bloodstream
- placenta
Likelihood of infection (2 types)
- Infectious Dose (ID 50)
- Lethal Dose (LD 50)
number of organisms necessary to cause illness in 50% of infected individuals
Infectious Dose (ID 50)
number of organisms necessary to kill 50% of infected individuals
Lethal Dose (LD 50)
the degree of pathogenicity of an organism
Virulence
It’s not enough to get there, you have to stick and stay stuck to cause disease
Adhering to a body surface
Pathogens make adhesions (also called _______) that
bind to cell surface receptors (viral “________”, pili, bacterial capsules, specialized attachment structures)
- ligands
- “spikes”
Examples of pathogen adhesion
- whooping cough
- Streptococcus mutans
Some pathogens stay where they stuck (ie whooping cough)
and don’t invade. Others move into new cells and tissues or into the bloodstream
Invading the body
some make _________ which stimulate phagocytosis
invasions
invasions that stimulate phagocytosis
TB, shigella, salmonella
some secrete ___________ to break down surrounding cells and tissues
enzymes
It includes phagocytosis and the immune system
Host defenses
the capability of a pathogen in evasion of phagocytosis
- Evading the body’s defense mechanisms
strains of bacteria with the thickest capsules are
most _______
virulent
Evading the body’s defense mechanisms
a. Host defenses include phagocytosis and the immune system:
b. Evasion of phagocytosis
c. Capsules
d. Ability to live after being phagocytosed
e. Immune System (antibodies)
f. Evasion via antigenic variation
g. Secretion of enzymes to destroy antibodies
Pathogen starts to obtain nutrients and begin to reproduce
Multiplying in the host
reproduction of the pathogen that causes disease
Multiplying in the host
how pathogens damage tissue and cause disease
Pathogenesis
this secretion breaks down cells and tissues, and stimulates inflammatory response
Enzymes
most damage in causing disease is done by
Toxins
poisonous substances produced by certain bacteria
Toxins
two kinds of toxins
- Exotoxins
- Endotoxins
are proteins, secreted by living bacteria
Exotoxins
Secreted proteins from certain types of bacteria (gram positive and gram negative)
Exotoxins
this toxin is extremely toxic
Exotoxin
this toxin is secreted outside the cell
Exotoxin
this toxin has highly specific effects on host depending on the type of toxin
Exotoxin
Examples of Exotoxins
- Botulinum toxin
- Tetanus toxin
- Salmonella enterotoxin
Usually the main cause of pathogenesis when they are present
Exotoxins:
- Botulism
- tetanus
- cholera
- pertussis
- anthrax
are lipids, released from the cell
membrane when cells die
Endotoxins
Lipopolysaccharide (LPS) portion of cell membrane of Gram-negative bacteria
Endotoxins
Endotoxins are the ___________ portion of cell membrane of Gram-_______ bacteria
lipopolysaccharide, negative
T or F
All endotoxins produce the same signs and symptoms
True
T or F
Exotoxins stimulate release of cytokines
False
Endotoxins
T or F
Pathogen leaves through a “Portal of Exit” to reach yet another organism
True
Portals of Exit (Often the same as the portal of entry)
nose, anus, genital tract, blood
Saliva usually contains a mixed flora of about __________.
108 organisms per milliliter
It carries the most prolific flora in the body
Colon
In the adult, feces are ___% or more bacteria by weight (about ______ organisms per gram).
25%
1010 organisms/g