M2: Intro to Medical Microbiology: Basic Science Aspects Flashcards
Organisms that cause most infectious diseases (4)
viruses
bacteria
fungi
parasites
Koch’s Postulates:
Purpose: To identify the _
The organism should always be _.
The organism can be _.
The organism _.
The same organism can be _.
organism causing an infectious disease
found in the diseased animal but not in healthy animals
isolated and grown in pure culture away from the animal
isolated in pure culture causes the same disease when re-inoculated into susceptible animals
re-isolated from those diseased animals
Limitations of Koch’s postulates include:
Some organisms can’t _.
There are no _.
Some diseases (e.g., pneumonia) can be caused _.
_: some animals/humans can be colonized by a “pathogen” _.
Alternative approaches: _
be grown away from animal hosts
animal models for some human diseases
by multiple organisms
Carrier states
without developing disease
epidemiology
Molecular Koch’s Postulates:
Purpose: To identify whether a factor produced by a pathogen , i.e., to identify “”.
Virulence is _.
Examples of virulence factors (3)
The set of virulence factors an organism produces determines _. Example: E. coli.
Using animal models, it is possible to measure virulence by determining _ or _.
is important for causing disease
virulence factors
the number of organisms it takes to start an infection
Toxins, adhesins, capsules, etc.
what type of disease it causes
Lethal Dose 50 (LD50)
Effective Dose 50 (ED50)
Molecular Koch’s Postulates include:
The phenotype or property encoded by the virulence gene should be associated with _.
Specific inactivation of the virulence gene encoding the suspected virulence trait should lead to _.
Addition of a cloned copy of the wild-type gene to the mutant should _.
pathogenic strains
a measurable loss of virulence
restore virulence
How can you specifically inactivate a microbial gene in order to perform Molecular Koch’s Postulates?
Example: can use _ as an experimental tool for _.
Transposons are _.
If a transposon inserts into a gene, there is a good possibility that gene will be _.
Therefore, transposons can be introduced as a means to _.
transposons
gene inactivation
small pieces of DNA that can insert into other DNA
inactivated
inactivate virulence genes
An illustration of molecular Koch’s postulates:
Hypothesis: Cholera toxin is a virulence factor for the bacterium, Vibrio cholerae (the cause of cholera).
Test this hypothesis using Molecular Koch’s postulates:
a. Is cholera toxin produced _?
b. Does inactivation of cholera toxin genes _?
c. Does addition of wild-type cholera toxin genes to that cholera toxin mutant _?
d. Conclusion from all answers being yes: cholera toxin is a virulence gene for V. cholerae.
by most pathogenic V. cholerae isolates
decrease the virulence of V. cholerae in animal models
restore virulence
Microbial Pathogenesis:
In the human body, pathogens face a constant struggle against _ and _.
Successful pathogens usually devise _.
Colonization of the body by a pathogen (does/does not) always lead to disease, e.g., the _. _ can be an important reservoir for _.
There are two kinds of infectious disease: _ vs. _
Disease results from damage caused directly by _ (e.g., toxins) or by _ responses.
other microorganisms (the normal flora) and host defenses
strategies to overcome the normal flora and host defenses
does not
carrier state
Carriers
future infections
Infection vs. Intoxication
pathogen factors
host immunopathologic
Many (but not all) infectious diseases result from pathogens completing the “_”, which can include:
a. Pathogen _ into the body
b. Pathogen _ and _
c. Pathogen _ through the _ (sometimes)
d. Pathogen _
e. _ (toxins or immunopathology)
f. _ of pathogen so it can _
infectious cycle
entry
adherence and colonization
invasion
epithelium
evasion of host defenses
Cell/tissue damage
Dissemination
infect a new host
There are advantages and disadvantages to intracellular (vs. extracellular) growth:
Advantages: _ are supplied, the pathogen is _ (at least initially) and some _.
Disadvantages: mammalian cells are _, so persisting/growing inside a host cell requires a good _, often requiring _ and requiring factors encoded by a lot of the _.
nutrients
protected from immune system
antibiotics
pretty good at killing invaders
strategy
expenditure of considerable energy
pathogen’s DNA
Intracellular vs. Extracellular Pathogens:
The choice of an intracellular vs. extracellular lifestyle often affects the _ and _ of a pathogen.
There are two types of intracellular pathogens: (2)
pathogenic strategy
antibiotic sensitivity
facultative
obligate
Examples of Predominantly Intracellular vs. Extracellular Pathogens:
intracellular obligate viruses
all
Examples of Predominantly Intracellular vs. Extracellular Pathogens:
intracellular facultative viruses
none
Examples of Predominantly Intracellular vs. Extracellular Pathogens:
intracellular obligate bacteria (3)
Myobacterium leprae
Chlamydiae spp.
Rickettsia spp.
Examples of Predominantly Intracellular vs. Extracellular Pathogens:
intracellular facultative bacteria (5)
Salmonella spp. Shigella spp. Listeria monocytogenes Legionella spp. Myobacterium tuberculosis
