Micro Exam 4 total

relatively how many microorganisms are pathogens?

few

virulence factors

distinct characteristics that allow avoidance of body defenses to increase reproduction, and transmit to the next host

normal microbiota

community of microorganisms found in/ on body of healthy individual

resident microbiota

inhabit sites for extended periods

transient microbiota

inhabit temporarily (hours-days)

-host innate and adaptive defenses

-competition and antagonism

a significant contribution to protection against pathogens via

comepetition

-covering binding sites

-consumption of available nutrients

-production of toxic compounds

Dysbiosis

when resident microbiota are killed or suppressed, the competition is eleminated and pathogens can colonize

adaptive immune system

defense mechanism that targets unique pathogens and creates long-lasting immunological memory

cross reactive immunity

antibodies produced against normal microbiota that cross react with pathogens

Cross-reactive immunity occurs when the immune system recognizes and responds to antigens from different sources due to structural similarities

parasite

an organism that recieves benefits at the expense of a host

pathogen

bacterial, viral and fungal parasitic agents of disease. any infectious biologicla agent that causes disease

Ectoparasites vs. Endoparasites

Ectoparasites live on the outside of an organism

Endoparasites live inside organisms

when does an infection occur ?

when a pathogen or parasite enters or begins to grow on a host

disease

any prolonged abnormal condition in which host cells are damaged and symtoms and/or signs of illness are present

host

an organism that harbors another organism either on or within itself

disease is dependendent on what 3 things

on charachteristics of the host, pathogen, and enviornment

disease is characterized by what

signs- objective evidence of infection (fever, rash, pus, swelling)

symptoms- subjective effects experienced by patient ( nausea or pain)

immunopathogenesis

immune response to a pathogen is a contributing cause of pathology and disease

to fully understand any infectious disease, researchers must study what

both pathogenic mechanisms of the pathogen and the disease symptoms/ signs caused immunopathogenesis

colonization

a microbe establishing itself and multiplying

The term infection can be used to

refer to a pathogenic microbe that colonizes, establishes, and multiplies

infection does not always lead to...

disease

subclinical infection

pathogen establishes and replicates in the host but at low levels that do not produce obvious signs and symptomsno or very mild signs or symptoms

colonization =

no pathogens

infection =

pathogens

carriers may unknowingly harbor and spread what

infectious agents in the absence of signs and symptoms

primary infection, and what is it caused by?

initial infection in a healthy individual , caused by a priamry pathogen

primary pathogens cause what

disease in a healthy individual

secondary infection and what its caused by

damage from a primary infection (or treatment of ) can predispose an individual to a secondary infection caused an opportunisic pathogen

opportunitunistic pathogens cause disease only when

The body's immune defenses are compromised or when introduced into an unusual location

opportunistic pathogens are typically members of

normal microbiota or common enviornmental microbe

Which pathogen is a common environmental microbe that can cause fatal infections in people with cystic fibrosis

pseudomonas aeruginosa

viral respiratory illness impairing barrier defenses can result in what

pneumonia

pathogenicity

an organisms ability to cause disease

infectivity

the ability of a pathogen to establish an infection in a host -> how easily the pathogen enters, survives, and multiplies in the host

virulence

the degree of harm or damage a pathogen causes to its host -> how severe the disease is

transmissibility

the process of spreading from one host to another -> how easily a pathogen is transmitted between hosts

virulence

a measure of the degree, or the severity of disease (signs and symptoms) in a host

invasiveness

ability to spread within a host

toxigencity

ability to produce toxins

highly virulent bacterial strains cause what

severe disease

infectivity -> ____ dose

infectious ID 50

number of cells/ virions required to cause infection in 50% of hosts

the lower the number means the less number of pathogens required to cause infection

lower number= more dangerous

virulence -> ____ dose

lethal LD50

number of cells/virions required to cause death in 50% of hosts

lower the number= more fatal

transmissibility -> _____ _____ number

basic reproductive number R0

average number of secondary infections caused by one infected individual in a population

R0

how easily a pathogen spreads in population is measured by Ro

The average number of healthy people that one sick person will infect

virulence factors are genes/ products that allow microbes to cause disease. helps with ...

-colonization: of a niche in the host

-entry into and exit out of cells

-invasiveness: the ability to spread within a host (tissue to tissue)

immunoevasion: evasion of the host's immune response

-immunosupression: inhibition of the hosts immune response

-obtain nutrition from the host

-toxixity: the ability of a pathogen to secrete a toxin

lysogenic conversion

virulence genes can sometimes be transferred horizontally or acquired through temperate phages

attenuation

the decrease or loss of virulence

what needs to overcome host defenses long enough to multipley and then exit host to infect another

successful pathogens

pathogenns and hosts are constantly struggling to keep up with each other in an evolutionary arm race, this concept is called what?

Red queens hypothesis

the infection cycle

describes the route of transmission of an infectious organism

horizontal transmission

passage from one person or animal to another within the same generation

horizontal transmission can be ___ or ____

direct (handshaking) or indirect (sharing contaminated objects)

formite transmission

Any inanimate object -> skin contact

vehicle transmission

ingetsted or inhaled materials like food water or air

verticle transmission

passage from a mother to her fetus during pregnancy

complex infection cycles often involve vectors as intermediates usually what?

arthropods

mechanical vector

carries the pathogen externally from one host to another without being infected itself

biological vector

becomes infected with the pathogen and then transmits it to another host, often after the pathogen undergoes part of its life cycle inside the vector

(like mosquito in malaria)

reservoir

an animal bird or arthropod that normally harbors the pathogen, often without exhibiting disease -> critically important for the survival of a pathogen

what virus is an example of a resevoir cycle

West Nile virus

amplifying host

a host in which the pathogen multiplies to high levels, increasing transmission risk

dead end host

an organism that becomes infected with a pathogen but does not contibute to further transmission of that pathogen to other hosts or vectors

incidental hosts

dead end hosts are also these

-an organsim that is not part of the normal transmission cycle but becomes infected accidentally. incidental hosts may or may not be dead end hosts

course of infection

the progression of disease within one host

incubation period

time between exposure and onset of illness (signs/ symptoms)

incubation time depends on what?

generation time of microbe

condition of the host

infectious dose

latent period

time between exposure and becoming contagious

prodromal stage

symptoms begin (vague symptoms like headache malaise = general feeling of illness

illness period

a period when signs and symptoms of disease appear

convalescence and what are some side effects

time when a person recovers from disease- some permenant damage may occur

-immune system

-medical treatment

acute infections

symptoms develop quickly, last a short time (strep throat)

persistant infections

chromic infections :can develop slowly, last moths/years

latent infections : similar to acute, but pathogen never eliminated , it can reactivate later

decrease immunity may allow what to occur?

reactivation of a latent infection

what are some causes of reactivation

age ( shingles is more common in people over 50

- weakened immmune system

-certain medications

(corticosteriods)

acute infections are a result of ___ infections usually in ___ duration

-productive infetions

short

persistant infections are a result of the ___ ___ ___ in the host

pathogen continually present

two types of persistant infections

chronic infections - continuous production of low levels of virions/ cells

latent infections- viral genome (provirus) remains silent in host cell; can reactivate

herpes simplex virus is what type of infection?

latent infection

herpes simple virus moves up ______ and becomes latent in ___

cranial nerve

neuron

in herpes simplex virus, what is integrated into host chromosome

provirus

localized infection

microbe limmted to small area (boil caused by staphylococcus aureus

systemic infection

agent spread throughout the body- circulatory/ lymphatic system

a systemic infection can cause what 3 differnt types of immune responses

bacteremia- bacteria circulating in the blood

toxemia

viremia

sepsis

acute, life threatening inflammation caused by infectilous or products in the bloodstream

List Koch's postulates

limitation to koch's first postulate

subclinical infection -> carriers (infected idividuals do donot always display symptoms)

limitations to kochs second postulate

some organisms cannot be grown in laboratory medium (ex: treponema palladium)

limitations to kochs third postulate

suitable animal hosts not always available for testing

-subclinical infection may occur

moleculars Koch's Postulates rely on studying _____ ____

virulence factors (gene or product)

3 molecular koch's postulates

1) virulence gene or product is found in all pathogenic strains of the organism

2) mutating the virulance factor gene to disrupt function should reduce virulence

3) reversion or replacement of the gene should restore virulence to the strains

pathogenic mechanisms follow several differnt types of patterns (4)

1- produce toxins that are ingested

2- colonize mucous membranes, multiply and produce toxins

3-invasde host tissues and then produce toxins

4- invade host tissues avoid host defenses and multiply

____ _____ grows on canned foods, produce the neurotoxin botulinum

clostridium botulinum

pathogenic mechanisms follow what 4 general patterns

1) produce toxins that are ingested

2) colonize mucous membranes, multiply, and produce toxins

3) invade host tissues and then produce toxins

4) avoid host defenses, invade host tissues and multiply

what microbe causes tetanus

clostridium tetani

with tetanus, bacteria colonize wound and secreete _____

tetanospasmin

overview of macrophage immune response

how does yersinia pestis act on cells

virulence factors turn off the killing ability of macrophages once inside them then they multiply

-infected macrophages die and release bacteria

how do mycobacterium tuberculosis act on cells

macrophages engulf TB cells but are unable to destroy because of the mycolic acids in cell wall prevents a phagosome with lysosome

-bacteria leave phagosome and multiply within macrophage

to cause disease, pathogens must... (5 things)

-enter a host

-fins a suitable niche

-avaoid circumvent, or subvert normal host defenses

-multiply

-transmit to a new susceptible host