M2: Intro to Medical Microbiology: Basic Science Aspects Flashcards Preview

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Flashcards in M2: Intro to Medical Microbiology: Basic Science Aspects Deck (22)
1

Organisms that cause most infectious diseases (4)

viruses
bacteria
fungi
parasites

2

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

3

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

4

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)

5

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

6

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

7

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

8

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

9

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

10

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

11

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

12

Examples of Predominantly Intracellular vs. Extracellular Pathogens:

intracellular obligate viruses

all

13

Examples of Predominantly Intracellular vs. Extracellular Pathogens:

intracellular facultative viruses

none

14

Examples of Predominantly Intracellular vs. Extracellular Pathogens:

intracellular obligate bacteria (3)

Myobacterium leprae
Chlamydiae spp.
Rickettsia spp.

15

Examples of Predominantly Intracellular vs. Extracellular Pathogens:

intracellular facultative bacteria (5)

Salmonella spp.
Shigella spp.
Listeria monocytogenes
Legionella spp.
Myobacterium tuberculosis

16

Examples of Predominantly Intracellular vs. Extracellular Pathogens:

intracellular obligate fungi

few

17

Examples of Predominantly Intracellular vs. Extracellular Pathogens:

intracellular facultative fungi

most

18

Examples of Predominantly Intracellular vs. Extracellular Pathogens:

intracellular obligate parasites

few protozoa

19

Examples of Predominantly Intracellular vs. Extracellular Pathogens:

intracellular facultative parasites

most protozoa

20

Examples of Predominantly Intracellular vs. Extracellular Pathogens:

extracellular bacteria (3)

most gram+ bacteria (except Listeria monocytogenes)
Vibrio cholerae
Treponema pallidum

21

Examples of Predominantly Intracellular vs. Extracellular Pathogens:

extracellular fungi (1)

Cryptococcus spp.

22

Examples of Predominantly Intracellular vs. Extracellular Pathogens:

extracellular parasites (1)

Giardia spp.