Lecture 8-9 Gram negative bacteria (Part 2) Flashcards Preview

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Flashcards in Lecture 8-9 Gram negative bacteria (Part 2) Deck (42):
1

Shigellosis is primarily a disease in what age group?

Children

2

Is the infectious dose of Shigella large or small and why?

Small. They are very acid resistant and are able to survive the stomach acid 'sterilization process'.

3

What 2 main methods are used by Shigella to cause shigellosis?

1. Infecting the mucosal epithelium of the colon by bacterial-directed endocytosis of M-cells (specialized phagocytic cells of the gut)
2. They also can induce formation of actin-directed pseudopodia that thrust bacteria directly into adjacent mucosal epithelial cells without exposure to plasma proteins or phagocytic cells.

4

Is the infection local or systemic with Shigella?

Local. Local inflammatory ulceration of mucosal cells creates blood and pus in the stool. (dysentery)

5

What is the Shiga toxin?

An A-B toxin that cleaves ribosomal RNA, disrupting protein production in the cell.

6

What is the primary manifestation of Shiga toxin?

Damage to the intestinal epithelial cells.

7

What is Hemolytic Uremic Syndrome?

In a small number of patients (mainly young children), the shiga toxin gets into the blood stream in high enough concentration where it mediates damage primarily to the glomerular endothelial cells, resulting in renal failure. (Systemic)

8

What E. coli strain also contains a plasmid encoding a Shiga-like Toxin?

EHEC

9

Where does Shigella infect

Colon

10

Where does Salmonella infect?

The G.I. mucosa similar to Shigella

11

How does Salmonella typhi act?

It can break through the Gut epithelium and enter phagocytic cells which then act as Macrophage Taxis to take the pathogens throughout the body.

12

What the is the method by which enteric gram negative bacteria are spread throughout the body after inserting themselves inside the macrophage.

1. They block lysosome fusion and multiply within the phagosome of machrophages
2. Hitch a ride into draining lymph nodes, bloodstream, or other tissues (all while being protected from immune system)
3. released upon the death of the macrophage causing bacteremia and infection.

13

Enteric Fever caused by bacteremia is also called what?

Typhoid Fever

14

Typhoid Mary was an example of what?

A permanent carrier of Typhoid fever

15

Most infections of Salmonella result from what?

Ingestion of contaminated food products

16

What age group does Salmonella infections affect?

All age groups

17

Is the infectious dose small or large for Salmonella and Why?

Large. Salmonella is very sensitive to stomach acid and requires a large does to become infected. This is contrary to Shigella

18

Is Salmonella infection local or systemic?

generally causes a localized infection of the small intestine mucosal epithelium.

19

How does the normal GI flora E. coli become pathogenic?

Genes that code for virulence factors can be transferred to non-pathogens including common GI normal flora such as E. Coli

20

Name the four pathogenic strains of E. coli

Enterotoxigenic E. Coli (ETEC)
Enterohemorrhagic E. coli (EHEC O157:H7)
Enteropathogenic E. coli (EPEC)
Enteroinvasive E. coli (EIEC)

21

2 characteristics of ETEC?

V. cholera exotoxin gene
Watery diarrhea

22

3 characteristics of EHEC?

Shiga-like exotoxin gene
Bloody dysentery
Hemolytic Uremic Syndrome (HUS)

23

3 characteristics of EPEC?

Shigella exotoxin gene
Adherence gene
Diarrhea

24

2 characteristics of EIEC?

Invasive genes
Dysentery

25

Most gram negative rods that produce UTIs originate where?

In the colon, contaminate the urethra and ascend into the bladder

26

UTI is an ____________ infection

Ascending

27

What is the most common cause of UTIs and why?

Uropathogenic strains of E. coli
They produce specialized adhesions that allow them to adhere within the urinary track.

28

What bacteria causes Plague rather than a GI infection in humans?

Yersinia pestis

29

Yersinia pestis causes a local or systemic infection?

Systemic with a high mortality rate.

30

What type of host are humans considered to be in Y. pestis infections

Accidental hosts. Infections are primarily Zoonotic

31

What are the typical hosts for Y. pestis

Rats, rodents and fleas

32

How is Y. pestis spread from a flea?

The bacteria replicate rapidly in the midgut of the flea. They eventually block the midgut and the next time the flea feeds it regurgitates into the fleabite.

33

What main exotoxin is used in Y. pestis

Superantigen

34

What is a necrotic bubo?

A dead lymph node which is a result of Y. pestis quickly replicating in a lymph node

35

What occurs with Y. pestis if the primary infection occurs in the lung?

Pneumonic plague

36

Immunity to cholera is a good example of what?

the value of maternal passive immunity

37

Is Vibrio Cholera resistant or sensitive to stomach acid?

Sensitive

38

Is Vibrio cholera invasive or non-invasive?

Non-invasive

39

What is the result of an infection of V. cholera?

A-B toxin enters the cells and activates adenylate cyclase, resulting in hypersecretion of water and electrolytes. Mortality rate falls from 60% in infants to 1% if promptly treated with replacement fluids and electrolytes

40

T or F, Antibiotics are secondary to fluids in a V. cholera infection/

True

41

What is the danger of synthetic infant milk formulas in some parts of the world?

In some communities sIgA immunity provided by mother's milk is the only defense in babies against contaminated water and food. Synthetic infant milk formulas do not provide this protection.

42

Babies are most vulnerable to pathogens during what time?

During the "window of susceptibility". This is a time when the maternal IgG is largely lost while the neonatal IgG levels are still low