Final SA

Question 1

What is the name of the organism that causes anthrax?

Answer 1

bacillus anthracis

Question 2

If individuals who develop inhalation anthrax are not treated promptly, what is the likely outcome of this disease?

Answer 2

shock and ultimately death

Question 3

Briefly outline how spores travel from the lung to the mediastinal (draining) lymph nodes, what happens to them when they get there, and how the organs subsequently disseminates. What virulence factors allow this organism to (i) avoid phagocytosis by macrophages and neutrophils, and (ii) cause the outcome in (b), above

Answer 3

Spores in lung taken up by phagocytic cells, and transported to the mediastinal draining lymph nodes.
Spores germinate, vegetative bacteria encapsulated (resist innate immune response), initiate bacteremia, produce exotoxins that cause shock, death.
The virulence factor that allows this organism to avoid phagocytosis is its polypeptide capsule.
It’s exotoxins are what cause shock and death.

Question 4

What are the two characteristics that distinguish virulent strains of Vibrio vulnificus from strains of this organism that do not cause primary septicemia?

Answer 4

encapsulated, fast growing

Question 5

Explain how a lack of either, or both, of the virulence factors identified in (a) might render V. vulnificus unable to cause primary septicemia.

Answer 5

Encapsulated protects bacteria from phagocytosis and complement mediated killing.
The concentration of stuff in the blood is more when the bacterium is fast growing. Concentraiton of endotoxin in the blood is more.
A lack of either of these would allow the innate immune system to gain control of the bacteria and shut down the infection.

Question 6

Outline the stages of the host–pathogen interaction that occur when a person develops primary septicemia after eating raw shellfish contaminated with V. vulnificus.

Answer 6

1) entry into host
2) adherence to GI epithelium
3) extracellular growth
4) invasion of local tissues in GI tract
5) disseminates extracellularly in blood causing endotoxemia
6) immune response

Question 7

What critical piece of information uncovered in patient history led the physicians to suspect malaria?

Answer 7

travel history

Question 8

What two characteristics of Plasmodium species would the physical need to consider when designing a treatment regimen for this patient?

Answer 8

drug resistance

latent or active infection

Question 9

Briefly outline the roles played by the sporozoite and merozoite forms of the malaria parasites during infection of a naïve human host, and explain how they cause the signs and symptoms of malaria.

Answer 9

• Infection begins when the sporozites are introduced into the blood stream by the mosquito. The sporozoite form is the form produced in mosquitos.
• The target organ is the liver. Once they reach the liver they mature into merozoites.
• Eventually heptocytes break open and release merozites into blood. Then they infect RBCs
• RBCs lyse and release more merozites
• The lysis of RBC results in anemia; RBC debris triggers cytokines production.

Question 10

What kind of microorganism is G. lamblia?

Answer 10

protozoan parasite

Question 11

What are two eukaryotic microbes that cause disease upon localized infection of the human GI tract?

Answer 11

Cryptosporidium parvum and cyclospora cayetanensis

Question 12

What clinical signs and symptoms are commonly associated with localized infections of the gastrointestinal tract?

Answer 12

Nausea, vomiting, abdominal pain/cramps, diarrhea (watery, or bloody), may or may not be accompanied by fever

Question 13

In the context of food borne illness, what is meant by direct intoxication?

Answer 13

Exotoxins are made by bacteria that grow in food prior to its consumption. Disease caused directly by exotoxin in food, NOT by infection with bacteria

Question 14

What type of outbreak, or epidemic, would be associated with disease caused by
this mechanism?

Answer 14

common source

Question 15

Give three, named examples of pathogens that can cause foodborne illness by direct intoxication, and for each one indicate whether or not it can also cause disease upon localized infection of the GI tract.

Answer 15

Clostridium Botulinum - Can cause disease upon localized infection of the GI tract in infants (infant botulism)
Staphylococcal food poisoning (Staphylococcus Aureus) cannot cause disease upon localized infection of GI tract.
Bacillus cereus food poisoning (Emetic form) can cause disease upon localized infection of the GI tract.

Question 16

What is the reservoir for L. monocytogenes?

Answer 16

Environment, animals, humans

Question 17

On which class of major histocompatibility complex with L. monocytogenes antigens be presented by macrophages?

Answer 17

MHC 1

Question 18

Briefly outline the sequence of events in the adaptive immune response that begins after L. monocytogenes is first detected in the tissues and which culminates in the clearance of the infection.

Answer 18

1) Dendritic cells in the tissues take up the L. monocytogenes antigen and migrate to the local draining lymph node, and activate naïve CD8+ T-cells, which undergo clonal expansion and differentiate into cytotoxic T-lymphocytes.
2) The cytotoxic T-lymphocytes are released into the blood circulation and move to sites of infection.
3) Cytotoxic T-lymphocytes recognize infected host cells via pathogen-specific antigen presented on MHC I and kill them.

Question 19

How are N. meningitidis infections acquired?

Answer 19

Enter the respiratory tract via infected or colonized humans

Question 20

What are the principle virulence factors of N. meningitides?

Answer 20

Polysaccharide capsule

Endotoxin

Question 21

Briefly outline the sequence of events in the host–pathogen interaction that occurs between entry of N. meningitidis bacteria into the body, and the onset of meningitis in an affected person.

Answer 21

1. Enters through aerosol droplets
2. Adheres to respiratory tract cell wall
3. N. meningitidis enters cell through transcytosis
4. Inflammatory response
5. Localized infection results due to inability of innate immune system to eliminate the infection cause of virulence factors (poly capsule)
6. Infection disseminates through blood as adaptive immune system tries to fight it. Don’t need to go through draining lymph node.

Question 22

To what family of bacteria does Y. pestsis belong?

Answer 22

Enterobacteriaceae

Question 23

How is Y. pestis transmitted to humans from reservoir animals?

Answer 23

Transmitted among reservoir animals and to humans (most commonly) by infected fleas.

Question 24

Briefly outline what happens to the bacteria after they enter a naïve human host by the route identified in part (b), how they travel to the draining lymph node and what happens when they get there, and how subsequently pneumonic plague can develop in the infected person.

Answer 24

1) Flea bite
2) Dendritic cells in the body take up the bacteria.
The bacteria that is phagocytosed blocks phagolysosome fusion.
3) Dendritic cells migrates to draining lymph node.
4) The bacteria grow in vacuole, express antiphagocytic factors (capsule, injectable toxins), released into lymph node. (When released it’s in a different form)
5) Endotoxic shock can result from rapid growth in the blood.
6) Travels to the alveoli in the lungs

Question 25

What is the reservoir of rabies virus?

Answer 25

animals and terrestrials mammals, bats

Question 26

By what means is rabies virus most commonly transmitted from the reservoir to humans?

Answer 26

animal bites

Question 27

What is rabies PEP, and how, specifically does it prevent neurological rabies from developing in a person who has been exposed to rabies virus?

Answer 27

The rabies virus specifically traverses the muscle cell gap to get into the nerve cells through the neuromuscular junction. The antibody (immunoglobulin) binds to the virus and and neutralizes (prevents from binding to the target cell) it to protect us right away. The injection of the inactivated virus is used to stimulate the adaptive immune response so that we may generate our own antibodies for protection. Because the virus is neutralized, and antibody fills in the place of the neuromuscular gap, the virus can no longer bind to the receptor site on the nerve cells.

Question 28

What is meant by the term ‘endemic’ as it relates to a pathogen?

Answer 28

The pathogen is a naturally occurring pathogen

Question 29

What is a dimorphic fungus?

Answer 29

Fungi which can exist in two forms.

Question 30

Briefly outline the host–pathogen interactions that lead to a systemic mycosis, and identify the similarities and differences that apply to Histoplasma capsulatum and Blastomyces dermatitidis.

Answer 30

1) entry to host through inhalation of spores
2) Adheres to respiratory tract cell wall
3) Enters host cell (Histoplasma capsulatum). Blastomyces dermatitidis (extracellular growth)
4) Cell and tissue damage
5) Immune Response
6) Dissimination by Trojan Horse (Histoplasma).
7) Histoplasma infect liver, spleen. Blastomyces infects skin and bones

Question 31

Give two examples of sexually-transmitted pathogens for which routine immunization is available in the United States.

Answer 31

Hep B virus and HPV

Question 32

Sexual transmission is an example of a horizontal transmission route. What, in contrast, is meant by vertical transmission?

Answer 32

Transmission of pathogen from parent to offspring

Question 33

For pathogens that are horizontally transmitted by sexual activity, list the potential routes by which vertical transmission might occur, and give one, named example of such a pathogen for each route

Answer 33

1. placental-fetal= (Treponema Pallidum)
2. Maternal parturition= (Chlamydia trachomatis, Neisseria goorrhoeae, herpes simplex virus)
3. Maternal- neonatal= Hep B virus, HIV

Question 34

What organism is most likely to cause severe influenza?

Answer 34

Influenza A virus (H1N1, H3N2)

Question 35

What are the two different types of vaccine used in the U.S. for routine immunization against influenza?

Answer 35

IIV - inactivated influenza vaccine

LAIV - live attenuated influenza vaccine

Question 36

Give examples of four characteristic clinical signs or symptoms of influenza, for each one indicate whether it is, or is not, a constitutional symptom

Answer 36

• fever/chills - constitutional
• myalgia - constitutional
• non-productive cough - not a constitutional symptom
• loss of appetite - constitutional

Question 37

What is the name of the disease caused by C. psittaci?

Answer 37

Psittacosis - Parrot Fever

Question 38

Why is penicillin (and related antibiotics) ineffective in treating C. psittaci infections?

Answer 38

lack of peptidoglycan in cell wall.

Question 39

Briefly outline the stages in the interaction between C. psittaci and host cells that leads to the release of newly replicated bacteria.

Answer 39

1) Tissue tropism determed by cell-specific receptors.
2) EB endocytosed into vesicle (fusion with lysosomes blocked)
3) EB changes into metabolically active intracellular form, reticulate body (RB)
4) RBs grow inside vesicle, change into EBs, then released by extrusion/lysis

Question 40

What are two examples of diseases that can be caused by invasive GAS?

Answer 40

• necrotizing fasciitis

- streptococcal toxic shock syndrome

Question 41

Explain how highly virulent strains of GAS are able to avoid the humoral adaptive immune response.

Answer 41

Antiphagocytic capsule with hyaluronic acid capsule. Basically acts as a self molecule. Mimicking you and therefore you can’t raise an antibody response against that capsule.

Question 42

The innate immune response normally results in infiltration of neutrophils and clearance of bacteria from infected tissues. What two aspects of this process are counteracted by invasive GAS strains, and what are the specific virulence factors involved?

Answer 42

Antiphagocytic capsule
anticomplement factors
Enzymes that block neutrophils- streptokinase and streptococcal chemokine protease

Group A strep Strains have a antiphagocytic capsule that prevents against phagocytosis by neutrophils. Some also have proteins with anticomplement (C3b and C5a) functions. C3b is large complement and C5a is small signaling molecule (chemokines) They secrete the enzymes hyaluronidase and lipase to breakdown once inside. Streptococcus pyogenes secretes streptokinase and streptococcal chemokine proteases which, when paired with antic-complement functions, block the abiilty of neutrophils to be called.

Question 43

Skin is an example of a barrier defense against pathogens. What are two other examples of barrier defenses?

Answer 43

• stomach acid

- mucus

Question 44

Most microorganisms that are normally found in the environment, and might enter a wound, are not pathogenic. Why not?

Answer 44

Most pathogens do not have the necessary virulence factors to overcome the immune system

Question 45

List the three types of pathogenic mechanism by which bacteria can cause disease after entering a wound, and give a different, named example bacterial species for each one.

Answer 45

• Disseminated infection- leptospirosis by Leptospira spp.
• Localized infection- Staphylococcus aureus v
• Systemic Intoxication from localized infection- tetanus by clostridium tetani