Topic 1-13 (Lecture 13)

Question 1

What is Mycobuacterium tuberculosis’ “nickname”?

Answer 1

TB

Question 2

What disease does M. turberculosis cause?

Answer 2

Tuberculosis

Question 3

What is tuberculosis?

Answer 3

Infection of the lungs, which causes an inflammatory reaction from the engulfment of bacteria by phagocytic cells

Question 4

How is tuberculosis spread?

Answer 4

Spread from person to person directly

Question 5

What problems to tuberculosis present to the immune system?

Answer 5

They persist and multiply inside macrophages; the cell-mediated immunity works but is NOT completely effective - bacteria can remain dormant, potentially leading to rapid reactivation in the future (that may or may not result in death)

Question 6

What type of people is TB most prevalent in?

Answer 6

Poor people and AIDS patients living in large cities

Question 7

What is the treatment of M. tuberculosis?

Answer 7

Long term (9-12 months) antibacterial therapy often with multiple antibiotics

Question 8

How resistant is M. tuberculosis to antibiotics?

Answer 8

Has widespread resistance; resistance to the main antibiotic, isoniazid has been observed. Some strains are resistant to all 8 “front-line” antibiotics in use”

Question 9

Is there a vaccine for M. tuberculosis, and if so, how does it work?

Answer 9

The TB vaccine uses a live strain of Mycobacterium bovis (BCG), which is immunologically similar (shares same antigens) with TB

Question 10

What is salmonella?

Answer 10

A range of very closely related bacteria that causes disease in humans and animals

Question 11

What are the general characteristics of salmonella?

Answer 11

Gram-negative
flagellated
facultatively anaerobic bacteria

Question 12

What are the 3 major antigens of salmonella?

Answer 12

H (flagellar) antigen
O (somatic) antigen
K (capsular) antigen

Question 13

How is salmonella transmitted?

Answer 13

From the feces of infected people or animals to others via contaminated food or drink

Question 14

What are the 2 disease associated with salmonella infections

Answer 14

Salmonellosis and typhoid fever

Question 15

How are salmonella divided into species?

Answer 15

Based of serology/serovars (using surface antigens)

Question 16

What are some virulence factors that salmonella havew?

Answer 16

Adhesins, LPS, capsules, two type III secretion systems, ability to invade and replicate inside host cells

Question 17

Where are genes encoding virulence factors found in Salmonella?

Answer 17

Pathogenicity islands (PAIs)

Question 18

How are pathogenicity islands acquired?

Answer 18

May have been acquired during evolution via horizontal gene transfer (ex. bacteriophage, prophages)

Question 19

What is SPI1?

Answer 19

Salmonella pathogenicity island 1. Contains genes associated with virulence genes and their regulation. (ex. inv genes, involved with invasion of host cells; type III secretion system used to inject proteins to mediate invasion and inflamation in eukaryotic cells)

Question 20

What individuals are at risk for Salmonella infections?

Answer 20

Those with little/no stomach acidity are at increased risk

Question 21

What diesease is caused by Salmonella enterica serovar Typhi? (AKA S. typhi)

Answer 21

Typhoid fever

Question 22

What are some characteristics of typhoid fever?

Answer 22

Pathogenic only to humans
transmitted by eating contaminated food or water
Often fatal disease

Question 23

What are symptoms related to typohid fever?

Answer 23

Nausea
Persistently high fever and chlils
Flushed appearance
Anorexia (vomiting)
Convlusions
delirium

Question 24

Where do S. typhiinfect the body?

Answer 24

Multiply in spleen and liver

Can move to gall bladder (thus are shed in bile)

Question 25

What is the incubation period of typhoid fever?

Answer 25

Week to a month (however, people may become asymptomatic carriers, or recover but become chronic carriers due to persistent bacteria in gall bladder)

Question 26

What disease does Salmonella enterica serovar Typhimurium (S. typhimurium) cause?

Answer 26

Thyphoid-like disease in mice | Self-limiting gastroenteritis (salmonellosis) in humans

Question 27

What is the incubation period of self-limiting gastroenteritis?

Answer 27

6-24 hours after ingestion; disease lasts up to 7 days

Question 28

What are symptoms of gastroenteritits?

Answer 28

diarrhea, abdominal cramps, vomiting, nausea Sometimes can enter bloodstream in immunocompromised or elderly people and cause systemic shock (often fatal)

Question 29

How is S. typhimurium transmitted?

Answer 29

By ingestion of contaminated food (most commonly chicken and eggs). Farm animals may become colonized yet are asymptomatic, thus potentially contaminating animal carcasses during slaughter

Question 30

Who was Typhoid Mary? (in a short abridged form)

Answer 30

Woman who worked as a hired maid/cook; healthy asymtomatic carrier that caused multiple outbreaks due to her carrying S. typhi. >Didn't believe she was at fault >Wouldn't stop working as a cook, even though told not to (by changing her name) >Got arrested twice, second time quarantined until she died >Shows that healthy carriers are dangerous, as there is no way to visually identify healthy carriers

Question 31

What is the difference between food poisoning and food infection?

Answer 31

Food infection - symptoms arise after pathogen has time to replicate in intsetine - can develop several days AFTER ingestion Food poisoning - results from ingestion of food contaminated with toxins - do NOT have to replicate in host/be alive

Question 32

How do Salmonella invade and infect mice?

Answer 32

Enter through "M cells" - cells that sample antigens from lumen of intestine Bacteria picked up by macrophages associated with Peyer's patches (lymph tissue of intestine) Bacteria replicate inside unactivated macrophages

Question 33

How does S. typhimurium cause diarrhea?

Answer 33

By injecting proteins into the intestinal cell via type III secretion system (needle-like secretion apparatus) Virulence proteins disrupt normal cell function & promote internalization of bacteria Cell responds with chemokines, induces inflammatory response Neturophils arriving produce PROSTAGLANDIN that increase cAMP levels, which inhibits sodium ion uptake This results in Chloride secretion into intestinal lumen Charge imbalance results in osmosis of water into lumen, resulting in diarrhea

Question 34

What causes the abdominal pain associated with S. typhimurium infection?

Answer 34

Likely due to inflamatory response resulting from LPS recognition and cytokine release

Question 35

How is salmonella diagnosed?

Answer 35

Isolation of bacteria, which is then grown on selective and differential media and identified by biochemical tests Serotype identified by using polyvalent and specific antisera to identify O (cell wall) and H (flagella) antigens

Question 36

How do salmonella invade cells?

Answer 36

Use adhesins to adhere (ex. type I fimbriae, plasmid-encoded fibriae) Uses SPI1 system to cause actin filament rearrangements in host cell to cause "ruffles" to form in membrane, resulting in internalization of bacteria in endocytic vesicle

Question 37

How do salmnoella replicate within host cells?

Answer 37

Use SPI2 type III injector to inject endosome to prevent fusion with lysosome Endosome used as a "home" for salmonella to grow and multiply

Question 38

How does salmonella evade host responses?

Answer 38

By invading the cell: -Evade innate and adaptive immune responses By altering endosome: -Prevent intracellular killing

Question 39

How is salmonella treated?

Answer 39

S. typhimurium or S. enteritidis infection usually resolve within a week and DO NOT REQUIRE TREATMENT (antibiotics used to control infection that spread beyond intestines) Re-hydration therapy may be needed for those with severe diarrhea S. typhi typically are treated with chloramphenicol and ceftriaxone (antibiotics)

Question 40

How is infections by S. typhimurium and S. enteritidis prevented?

Answer 40

Prevented by proper sanitation & handling and cooking of foods Focus is on detection of bacteria and food and public education Vaccines for chickens are being to developed

Question 41

How are S. typhi infection prevented?

Answer 41

Vaccines; 3 vaccines exist, which 2 injected and one orally administered