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Medical Microbiology > Lecture 10 > Flashcards

Lecture 10 Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

What are the characteristics of invasive Enterobacteriaceae pathogens?

A

gram- rods causing intestinal disease in the large intestine (sometime part of small intestine) leading to bloody diarrhea

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2
Q

What is the reservoir for invasive Enterobacteriaceae pathogens?

A

animal or human microbiota

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3
Q

What is a common form of treatment against invasive Enterobacteriaceae pathogens causing diarrhea?

A

antibiotics

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4
Q

What are the 3 species of bacteria that causes dysentery diarrhea?

A

Shigella (and closely related EIEC strains), Salmonella and EHEC noninvasive strain

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5
Q

How are Shigella and EIEC similar?

A

Shigella is another variant of E. coli

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6
Q

What are two types of Salmonella diseases?

A

Salmonellosis (dysentery diarrhea) and typhoid fever (non-enteric disease)

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7
Q

What disease does a non-invasive EHEC strain cause?

A

hemorrhagic colitis

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8
Q

What is dysentery?

A

disorder of digestive system (large intestine or colon) resulting in severe diarrhea (contains blood, mucus, and pus in feces)

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9
Q

What is dysentery characterized by?

A

frequent pooping includes cramps and pain

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10
Q

What are the 4 Shigella species?

A

S. dysenteriae (serogroup A) = A dyss (diss) | S. flexneri (serogroup B) | S. boydii (serogorup C) = Chef Boy(ar)dii | S. sonnei (serogroup D)

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11
Q

What are the characteristics of Shigella?

A

non-motile; same characteristics as E. coli

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12
Q

Where is S. flexneri common in?

A

most studied out of the 4 species; common in developing countries (we Be “flexin” on developing countries = we “show off” how forward we are, Be = serogroup B)

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13
Q

Where is S. sonnei common in?

A

developed countries (ie: USA = California = always “sonnei” in California = vitamin D (serogroup D))

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14
Q

How common is Shigellosis?

A

very common

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15
Q

What age group do most deaths worldwide occur with?

A

kids under 10

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16
Q

How many Shigellosis cases/year in the US?

A

~450,000

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17
Q

What is the reservoir for Shigellosis?

A

strictly human = same for EIEC since they are similar

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18
Q

What are the 2 methods of transmission of Shigella?

A

direct contact and fecal-oral transmission

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19
Q

How does fecal-oral transmission occur?

A

water contaminated with feces or flies sit on feces and then sit on our food

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20
Q

What are the 3 symptoms of Shigellosis? How long does it take after infection for symptoms to develop?

A

abdominal cramps, fever, dysentery || 1-3 days

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21
Q

What is the Type II secretion system?

A

2-step process to deliver toxin from bacteria to inside host

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22
Q

What is the Type III secretion system?

A

secreted protein is delivered directly from microbe into host cell via an injection-like process that requires a complex of proteins called an “injectisome”

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23
Q

What is the 2-step process of the Type II secretion system in gram– bacteria?

A

toxin first secreted into periplasmic space and assembles into 4º structure &raquo_space; toxin transferred across outer-membrane to bind onto host-cell surface receptor to be taken in

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24
Q

How does Shigella use the Type III secretion system?

A

uses it to transfer proteins that cause the host cell to uptake the bacteria, involves the formation of the flagella to inject proteins through

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25
Q

What are the virulence factors of Shigella?

A

Ipa proteins, IcsA autotransporter, and Shiga toxin

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26
Q

What are the Ipa proteins as a virulence factor of Shigella?

A

group of proteins that are secreted via the Type III secretion system

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27
Q

What is the IcsA autotransporter as a virulence factor of Shigella?

A

protein that mediates intracellular motility by helps pathogen bind to the cytoskeleton of the host cell and uses it to move within the cell and spread onto neighboring cells

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28
Q

What is the Shiga toxin of Shigella?

A

AB exotoxin that kills intestinal epithelial and endothelial cells

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29
Q

What are autotransporter proteins?

A

proteins that don’t rely on a transport system because it transports itself

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30
Q

What is the invasion strategy of Shigella/EIEC?

A

INDIRECTLY invades epithelial cells by crossing between adjacent cells and invade Through the Basal Side of cell; can Directly invade M cells

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31
Q

What is the invasion strategy of Samlonella?

A

DIRECTLY invades epithelial and M cells

32
Q

What are M cells?

A

cells of the immune system

33
Q

What are 3 ways we can detect/diagnosis Shigella in an individual?

A

culture organism from fecal sample || perform biochemical assays and agglutination rxns || PCR-based assay

34
Q

What is the treatment of Shigellosis?

A

replacement of fluids with electrolytes while administering antibiotics to reduce severity and duration of the disease

35
Q

What vaccines are available for Shigellosis?

A

none, currently under development

36
Q

Why would you want to use antibiotics to treat Shigellosis?

A

damage is so severe = no time to wait for immune system to clear it up

37
Q

What are the differences in Salmonella species due to?

A

antigenic epitopes

38
Q

Which species of Salmonella are we discussing?

A

S. enterica serovar Typhimurium and S. enterica serovar Typhi

39
Q

What group does S. enterica serovar Typhimurium belong to?

A

Group B

40
Q

What group does S. enterica serovar Typhi belong to?

A

Group D1

41
Q

What do salmonella cells use to attach to their host cells?

A

pili

42
Q

What disease does S. enterica serovar Typhimurium cause?

A

Salmonellosis

43
Q

What is Salmonellosis?

A

gastroenteritis characterized by fever, nausea, vomiting, cramps, bloody OR non-bloody diarrhea

44
Q

What is the reservoir for S. enterica serovar Typhimurium?

A

human, livestock animals, lizards/reptiles

45
Q

What is the mode of transmission for S. enterica serovar Typhimurium?

A

zoonotic disease = can consume infected livestock (ie: chicken/eggs) or come into contact with infected animals

46
Q

How common is Salmonellosis in the US?

A

more than 1million cases/year

47
Q

What are the 4 virulence factors of S. enterica serovar Typhimurium?

A

2 adhesins = type 1 pili and curli (a type of pilus) || 2 Type-III-secretion systems = Sip proteins or Ssp proteins

48
Q

How many Type III secretion systems does S. Typhimurium have?

A

2

49
Q

Why would a pathogen need 2 different type-III secretion systems and not just one? (2 reasons)

A

regulate which of the 2 protein-groups need to secrete since not both are expressed at the same time || protein-group A is being used for pathogen-host-cell interaction and protein-group B will be used at different stage of infection

50
Q

What are ways to prevent Salmonellosis?

A

eliminating bacteria from food with proper cooking and vaccinating chickens using vaccine against S. enterica serovar Typhimurium

51
Q

What vaccine are available against S. enterica serovar Typhimurium?

A

none for humans thus far but one for chickens

52
Q

What is a treatment used against Salmonellosis?

A

use of antibiotics are NOT recommended; oral rehydration therapy

53
Q

What is S. enterica serovar Typhi?

A

similar to S. enterica serovar Typhimurium but found a way to escape the GI tract and infect other parts of the body

54
Q

What disease does S. enterica serovar Typhi cause?

A

Typhoid fever

55
Q

What is typhoid fever?

A

systemic disease infecting liver, spleen and bone marrow

56
Q

What are some symptoms of typhoid fever?

A

fever/headache, myalgias, anorexia, GI symptoms but not a true GI disease

57
Q

What is the reservoir for S. enterica serovar Typhi?

A

strictly humans = not zoonotic

58
Q

What is the method of transmission of S. enterica serovar Typhi?

A

indirect oral-fecal route

59
Q

How common is typhoid fever worldwide?

A

more than 15mil cases

60
Q

What is a characteristic of typhoid fever?

A

red spots seen on skin

61
Q

What samples must you collect to diagnose someone who is infected with S. enterica serovar Typhi and has typhoid fever?

A

blood sample = detectable during early stages of infection || fecal and urine sample = detectable during late stages of infection

62
Q

Why does the amount of S. enterica serovar Typhi decline in the blood as the infection progresses?

A

bacteria exits blood to move into other organ systems

63
Q

What is used to treat typhoid fever?

A

antibiotics

64
Q

In order to prevent typhoid fever, what are the 3 vaccines available for use?

A

must be vaccinated especially when travelling || whole-killed bacterial vaccine, Vi antigen vaccine, and oral live vaccine

65
Q

Why is the whole-killed bacterial vaccine for typhoid fever no longer recommended?

A

side effects emerged due to virulence factors present from the process of making the vaccine when the bacteria was killed

66
Q

What is the Vi antigen vaccine for typhoid fever?

A

isolated one of the protective virulence factors and incorporated it into a vaccine

67
Q

What is the Oral-live vaccine for typhoid fever?

A

attenuated the pathogen to be used as a vaccine

68
Q

What strain is the non-invasive EHEC that causes hemorrhagic colitis?

A

O157:H7

69
Q

What is the reservoir of EHEC O157:H7?

A

humans and animal = zoonotic disease

70
Q

What is hemorrhagic colitis?

A

initially secretory diarrhea followed by bloody diarrhea with cramps and no fever

71
Q

How many cases/year does hemorrhagic colitis occur in the US?

A

~73,000

72
Q

What is the mode of transmission of EHEC O157:H7

A

via contaminated food, usually undercooked ground beef, unpasteurized milk/juices, uncooked produce

73
Q

What are the virulence factors of EHEC O157:H7?

A

Shiga toxin and EaeA adhesin

74
Q

What does the EaeA adhesin do? What is the consequence of the action?

A

causes actin rearrangement which damages the host = no need to invade to cause damage

75
Q

What is a treatment against hemorrhagic colitis?

A

use of antibiotics (controversial = depends on views of doctor)

76
Q

What are 3 ways to prevent infection from EHEC O157:H7?

A

pasteurize dairy products (doesn’t sterilize), irradiate beef meat, good hygiene

Medical Microbiology (20 decks)

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