MB 411 Quiz 1

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Which of the following archaea are opportunistic pathogens of humans?

Archaea are not pathogenic to any host species.

Which of the following act as barrier defenses against the entry of pathogens into the body?

Eyes - Tears, Lysozyme
Respiratory Tract - Mucus, Ciliated epithelium, ALveolar macrophages
Genitourinary Tract - Urination, Acidity of urine, Lysozyme, Vaginal lactic acid
Skin - Anatomic barrier, Antimicrobial secretions (glands)
Digestive Tract - Stomach acidity, Normal flora, Bile

Cholera toxin is an example of a cytotonic enterotoxin. What is a cytotonic enterotoxin?

A toxin that does not cause the host cell to die; only changes are caused to the cell

Certain organisms, for example Salmonella Typhi, are able to establish a state of chronic
carriage in some individuals. What does chronic carriage mean?

Chronic carriage means that the host is permanently colonized with a pathogen. Overt disease need not be caused.

Which of the following is/are clinical signs of disease?

Temperature, Blood pressure, Heart beat, Pulse
NOT
Pain, hunger, etc

The Gram-positive bacterium, Clostridium difficile, an obligate anaerobe, can give rise to
endogenous infections that result in antibiotic-associated gastrointestinal disease. Which of the
following statements about C. difficile is/are correct?

Not normally found colonizing the GI tract
When ABs alter normal flora it can colonize GI tract, causing diarrhea and colitis

What kind of relationship does a commensal microbe have with its host?

Organism +/ Host 0
although it can be the other way around with the host benefiting, it is extremely rare

What happens when a pathogen infects a dead-end host?

A dead-end host is one in which the pathogen can no longer be transmitted.
Pathogen is either not shed or shed in insufficient quantities to infect a new host.

Diphtheria toxin is an example of a cytolytic toxin. What is a cytolytic toxin?

Cytolytic toxins result in direct death of host cell.

What class of microbial pathogens causes most endogenous infections of humans?

Some opportunistic pathogens

Which of the following is/are characteristics of organisms that establish exogenous infections in
humans?

All are obligate pathogens
Many opportunistic pathogens

Which of the following are characteristics of a facultative intracellular pathogen?

Facultative intracellular pathogens can reproduce inside OR outside of the host cell.
Always involves adhering to host cells - penetration not necessary

Excessive cytokine production causes which of the following immunopathologies?

Shock and body function disruption
Inflamation

The Gram-negative bacterium, Campylobacter jejuni is generally considered to have a low
infective dose in humans. What does it mean to have a low infective dose?

Low infective does means that a small inoculum of the pathogen is capable of causing disease and infection in a host. Its virulence must be high.

Which of the following mechanisms for local invasion of tissues potentially could be
employed by an obligate extracellular pathogen?

Hyaluronidase: degrades extracellular matrix and pathogens squeze down in between
Exotoxin secretion: kills epithelial cells and makes a void to breach in

Which of the following types of clinical specimens would not normally contain microorganisms
(i.e. the specimens come from normally sterile sites in the body)?

Normally sterile sites:
-Blood - CSF - Pleural fluid
-Peritoneal fluid -Pericardial fluid -Joint
-Bone -Muscle -Internal body site
-Other normally sterile site

The Gram-positive, spore-forming bacterium Bacillus anthracis is an obligate pathogen of
humans. What is an obligate pathogen?

An obligate pathogen is ALWAYS associated with disease when found a host.
Presence of organism = Disease

In the context of medical microbiology, the term "Parasite" refers specifically to which of the
following?

Non-fungal eukaryote that causes disease
Relatively large and complex
Uni- or Multicellular

Which of the following may be consequences of a failure by the immune system to resolve an
infection?

Death
Persistant Infection
Latent Infection
Reactivation

Which of the following are routes by which pathogens potentially can disseminate within the
body?

Blood
Lymph
Rarely - nerve cells

When present in a bacterium, which of the following could be virulence factors?

...

Which of the following are virulence factors commonly found among protozoan parasites?

...

Among viruses that commonly cause human disease, which of the following result in active
replication and production of new virus particles?

Lytic and non-lytic viruses

Which of the following are possible outcomes of viral interaction with a cell?

1. Abortive infection (Failed Infection)
2. Lytic Infection (Cell Death)
3. Persistent Infection (Replication without cell death)

In which of the following situations would an opportunistic pathogen be likely to cause disease?

1. Microbe has virulence factors
2. Large inoculum load
3. Access to normally sterile body sites
4. Weakened host immune system

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