Unit 4: Chapter 34 Flashcards
Host
larger organism that supports survival and growth of pathogenic microorganism
Infection
microbe growing and multiplying on or within a host
may or may not result in overt disease
Infectious disease
any change from a state of health
part or all of host incapable of carrying on normal function due to presence of pathogen or its product
Infection vs colonization
Infection: conditions from colonization of host that can cause disease
Colonization: denotes physical presence of microorganisms
___ can cause infections when opportunity given
colonization
Pathogen
any organism that cause disease
Opportunistic pathogen
may be part of normal microbiota and cause disease when host is immunocomprised
Pseduomas aeuroginosa
Not part of normal flora
Opportunistic pathogen
Extracellular pathogens
remain in tissues and fluids but never enter host cells during disease
Virulence
degree of harm (pathogenicity) inflicted on its host
Pathogenicity
ability of pathogen to cause disease
A pathogen must contact ______ and survive within it to cause _____
a host, disease
Intracellular pathogens
Grow and multiply within host cells
Faculative intracellular pathogens
reside within cells of host and can also grow without host cell support in pure culture
Obligate intracellular pathogens
reside within cells of host and needs host to reproduce and survive
Factors affecting success of transmission
- Virulence of organism
- Number of invading organisms
- Presence of adhesion and invasion factors
The best defensive system against pathogens is:
immune system based on healthy diet and exercise
Invading organism competes ____ for resources and survive host ______ ________
resident microbiota (normal flora) ; defense mechanism
Disease ensues when organism produces molecules that
directly damage ______ or stimulates ______
host cells
host immune cells to destroy infected tissue
Tranmission
entry into the host
Animate transmission
Living
(animals, humans)
Inanimate transmission
Nonliving
(water, food)
Reservoir
natural environment location in which pathogen normally resides
Vector
Organism that spreads disease from one to another
Mosquitoes, ticks, fleases, mites, biting flies are examples of
vector
Pathogen transmission occurs either _____ or ______
directly, indirectly
4 main routes of pathogen transmission:
- Airborne
- Contact
- Vehicle
- Vector borne
Vertical transmission
Pregnant women pass pathogen to their unborn child
(infected mother to child)
Examples of Direct transmission
horizontal contact (kissing)
airborne droplets
vector
vertical contact (mother to child)
Examples Indirect transmission (vehicles)
Contact (fomites)
Food
Water
Biological products
Airborne (droplet nuclei and aerosolized droplets like dust)
Fomites
inanimate objects that can carry disease
Ex. Table, microphones, door handles
Horizontal transmission
Transmission of infection from person to person
Horizontal Transmission through _____
7 F’S
1. Flies
2. Fluids
3. Food
4. Feces
5. Fingers
6. Fomites
7. Fornication
The efficiency of transmission increases with
extensive multiplication
Pathogens virulence may be influenced by its ability to
live outside its host
True or False: Exposure is enough to make infection to occur
False: infection is not enough to make infection!
Tropism
Pathogen must make contact with appropriate host tissue by cell surface receptors
Infection occurs by ___ and _____
exposure and tropism
Droplets
direct airborne transmission
produced when liquids are placed under force (saliva, mucus)
can travel up to 1 meter (why social distance exists)
up to 2 mm in diamter
Most human diseases are transmitted by the ___ system through any other system
Respiratory
Droplet nuclei
indirect airborne transmission
result from evaporation of larger droplets
may remain airborne for hours or days and travel long distances
1 to 5 um diamter
Dust particles
indirect airborne transmission
can survive long periods outside host
Droplet nuclei can reach
the lung
Tuberculosis (TB)
Caused by mycobacterium
Example of droplet nuclei
Patient cough into air release droplet nuclei which float into air and can last several hours to be inhaled by a person
Aerosolized dust particles
smaller than 1 um and can be dispersed way further
Contact transmission
host touching source or reservoir of the pathogen
Direct contact is
person to person
physical interaction is required
Indirect contact
involves inanimate objects (fomite) that transfers infectious agent between hosts
Vehicles
materials that indirectly transmit pathogens
Examples of vehicles
Surginal instruments
Drinking vessels
Food
Water
Biological materials (fluids and tissues)
Air
Vector
living organism that transmits a pathogen
highly virulent
Vector organisms include ___ and ___
mostly anthropods: insects, ticks, mites, flies
vertebrates: dogs, cats, skunks, bats
In vector borne transmission, pathogen benefit because ___ and ____
extensive reproduction
spread between hosts
Vector born diseases include
Malaria, typhus, and sleeping sickness
In vector borne transmission, pathogens do not harm what nd why?
their vector
because host and pathogen vector are closely related as reproduction connect the two
What is more common?
Vertical or horizontal transmission
horizontal transmission
Babies born with infectious disease from vertical transmission are said to have:
congenital infection
Ex. gonorrhea, symphillus, german measles, toxoplasmois, listeria, zika virus
Infectious Dose (ID50)
Number of microbes required to cause disease in 50% of inoculated hosts
Highly virulent pathogenns have ___ value of ID50 and LD50 than does moderately virulent one
lower
More virulent strain is identified as
Low ID50 and LD50
lower number of organisms needed to infect 50% of hosts
Vibrio cholerae
large infective dose (10^7) since it is easily destroyed by stomach acid
(higher number of organisms cause disease)
Shigella
requires very small infective dose
(small number of organisms cause disease)
Lethal Dose (LD50)
dose that kills 50% of a group of experiemntal hosts within a specified period
Lethal dose is influenced by
susceptibility of host by imune system, nutrition, cleanliness, and emotional health
__ and _____ establish colonization
entry, adhesion
Portal of entry for pathogens
- skin
- respiratory
- gastrointestinal
- urogenital system
- conjuctive of eye
Adhesion
cell-surface components that help bacteria attach to target cells
Adhesions have high degree of ___ to _____
specificity, target tissues
Microbial adherence structures:
- Pilli
- Fimbriae
- Membrane and capsular materials
- Specialized adhesion molecules on microbe’s cell surface
Bacteremia
presence of viable bacteria in the blood
Invasion
once under mucous membrane, a pathogen can penetrate deep issues
Septicemia
bacterial or fungal toxins in the blood
Clostridium tetani (Tetanus)
Noninvasive
Does not spread from oen tissue to another but toxins become blood borne
Bacillus anthracis (anthrax) and Yerinia pestis (Plague)
Highly invasive
Produces toxins
Invasion of intracellular bacterial pathogens use ______
actin filament tail
Actinn tail propels bacteria by
host cell surface where it forms protrusion and helps with invasion
Profusion from actin tail is engulfed by
adjacent cell and evades immune response
Pathogenicity Islands
Large segments of bacterial chromosomes and plasmid DNA to encode for virulence factors
Toxin
substance that disrupts normal metabolism of host cells
Toxigenicity
Pathogen’s ability to produce toxins
Intoxications
Diseases that result from entry of a specific performed toxin into host
Ex. S. aureus
What helps the pathogen survive host defenses?
Pathogenicity Islands
3 ways pathogenicity islands help survive host defenses
- increase bacterial virulence
- absent in nonpathogenic membranes of same genes and species
- genes can spread from one bacterial cell to another
Intoxications don’t require presence of ___ but require presence of ___
pathogen, toxin
Intoxication vs. infection
Intoxication: disease from entry of toxin and organism does not have to enter body
Infection: organism needs to enter body and go to target to attach to receptor
Exotoxins
AB toxin (2 subunit protein)
gram + and gram -
heat susceptible (not resistant)
more toxic
Endotoxins
Lipid A
Onlyn gram -
Heat stable and resistant
less toxic
__ are among most lethal substances known
exotoxins
How can exotoxins be transferred?
From organism to organism by genes on plasmids or prophages
AB toxin
In exotoxin and protein
2 subunits
1. A subunit: catalyze reaction that cause toxicity
2. B subunit: binds to host cell receptor
Superantigens
Endotoxin
Stimulate about 30% of host T cells of immune cells which encode for cytokines and release proinflamatory molecules
Cytokines by T cells of superantigens result in
failure of multiple host organs
Endotoxin lipid polysaccharide located in
gram negative cell wall and is toxic to mammals
Why are endotoxins called endotoxins
Bound to bacterium and released when microorganism lyses
What causes fever?
endotoxin
The toxic componet in lipid portion of endotoxins is
Lipid A
