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Microbiology > Exam2Lec3EntericBacteria > Flashcards

Exam2Lec3EntericBacteria Flashcards

1
Q

Enteric bacteria general details:

A

Endotoxin (LPS) (more or less)

Motile or non-motile

Facultative anaerobic

Simple nutritional requirements
—Ferment glucose
—Reduce nitrates to nitrites
—Oxidase negative

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2
Q

What is the reservoirs of enteric bacteria

A

Ubiquitous

Humans
–Normal flora (endogenous)
–Diseases
–Carriers

Animals

Water

Soil

Vegetation

Exogenous portal of entry usually oral

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3
Q

What is used as a public health indicator of fecal contamination of water

A

Enterobacteriaceae–> e.coli and Coliforms that are only in the bowel

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4
Q

What is the morphology of coliform

A

gram negative rods

Lactose positive fermentation

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5
Q

What is the single cause of morbidity and mortality in the world

A

Diarrheal disease

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6
Q

In what population of groups what is the greatest of morbidity and mortality?

A

small children

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7
Q

Over ___ of children in many parts of ____ ____ die before the age of __, the majority with diarrhea associated illness.

A

10%, Latin America, 5

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8
Q

What are the two types of gastroenteritis?

A

Secretory (watery) diarrhea

Inflammatory diarrhea

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9
Q

What is Inflammatory diarrhea

A

Presence of white blood cells
-Neutrophils
-Mononuclear

Presence or absence of red blood cells

Fever

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10
Q

What bacteria can cause inflammatory diarrhea?
Explain given

A

Shigella

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11
Q

What is Secretory (watery) diarrhea

A

Absence of white blood cells

Absence of red blood cells

Watery, large volume

Nausea, vomiting

Afebrile

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12
Q

What bacteria can cause Secretory (watery) diarrhea? Example given

A

cholera

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13
Q

What is the morphology and the metabolism of E.coli

A

Gram (-) bacilli

facultative anaerobe

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14
Q

E.coli is classified into ____

A

serogroups by O, H and K antigen

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15
Q

What does the serogroup O stand for

A

LPS

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16
Q

What does the serogroup H stand for

A

flagella

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17
Q

What does the serogroup K stand for

A

capsule

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18
Q

What is an example of serogroup (EHEC)?

A

O157:H7

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19
Q

Overview of E.coli pathotypes

A

Enterotoxigenic (ETEC) – heat stable (ST) or labile (LT) toxin stimulates hypersecretion of fluids in small intestine

Enteropathogenic (EPEC) – adherence and destruction (A/E lesions) of cells, decreased fluid absorption

Enterohemorrhagic (EHEC) – similar to EPEC but with shigatoxin, may progress to HUS
Others (EIEC, EAEC, UPEC)

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20
Q

Most common of e.coli pathotype

A

EAEC (dont care about)

EHEC ⭐️

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21
Q

Where is ETEC found?

A

Endemic in developing countries

causes about 1/5th of all diarrheal illness in humans (largely pediatric)

also individuals traveling from developed nations (i.e. traveler’s diarrhea)

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22
Q

ETEC can also be considered ?

A

traveler’s diarrhea

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23
Q

What is the transmission of ETEC?

A

fecal oral transmission

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24
Q

What is the symptoms of ETEC

A

Rapid onset of watery diarrhea from mild to cholera-like
nausea
vomiting
no RBCs or WBCs

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25
Q

What is the Virulence factors of ETEC?

A

heat-stabile (ST)
heat-labile (LT) toxins

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26
Q

What does ST toxin in ETEC cause

A

increase cGMP

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27
Q

What does LT toxin in ETEC cause

A

Increase cAMP

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28
Q

The increase of cGMP and cAMP causes what?

A

Increase cl- transport out of the cell and water goes with it

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29
Q

How do we treat ETEC?

A

Symptoms usually resolve without therapy

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30
Q

Where do we find EPEC

A

Infant diarrhea in underdeveloped countries

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31
Q

What does EPEC do?

A

EPEC adhere to epithelial cells lining small intestine (A/E lesions)

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32
Q

What are the symptoms of EPEC?

A

Malabsorption
watery diarrhea
usually without RBCs or WBCs

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33
Q

What does EPEC have to cause disease?

A

Type III (contact dependent) secretion system

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34
Q

Where is the Type III (contact dependent) secretion system

A

Location
-Channel spanning both membranes of Gram negative bacteria
-Two components fuse with
eukaryotic cell membrane to form
injection pore (needle-like)

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35
Q

What is the attachment that EPEC can adhere to the host cell called

A

BfpA

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36
Q

What is the effector that EPEC injects into cell?

A

TIR

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37
Q

What does TIR act as for EPEC

A

It acts as a receptor for Intimin (on the outside of EPEC)

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38
Q

what does TIR stand for ?

A

Translocated intimin receptor

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39
Q

Where is EHEC found

A

Predominantly in developed nations

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40
Q

What is the reservoir of EHEC

A

Cattle

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41
Q

Extra fun details of EHEC

A

Sporadic, usually outbreaks with common source

Forms A/E lesions like EPEC, usually not invasive

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42
Q

What is the usually the source of EHEC

A

Undercooked beef

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43
Q

What is the most common serotype of EHEC

A

O157:H7

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44
Q

What are the symptoms of EHEC

A

Watery diarrhea that may progress to bloody
cramps
fever may be absent

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44
Q

What is the Pathogenesis of EHEC

A

Forms A/E lesions like EPEC

Shiga toxin released

Inhibits host cell protein synthesis

Cell death

Possible dissemination and damage to kidney (HUS)

45
Q

What is the Virulence factor of EHEC

A

Shiga-like toxin

46
Q

How does the progression of EHEC occur?

A

-3 Days AFTER ingestion
1. Diarrhea
2. Abdominal Pain
3.Fever
4. Vomiting
-Days 0-6
1. Hemorrhagic colitis (bloody diarrhea)
-Day 7
1. 15% of cases=HUS
2. 85% of cases=Resolution

47
Q

How is e.coli diagnosis?

A

Culture on selective and differential medium, MacConkey agar

E.coli are lactose fermenters and would make the agar turn pink

48
Q

If EHEC suspected then how do we diagnosis ?

A

sorbitol-MacConkey (SMAC) agar
O157 are sorbitol-
most other E. coli are +

49
Q

What is the treatment of e.coli

A

usually supportive, fluid and electrolyte replacement

50
Q

What is the morphology and the metabolism of V. cholerae

A

Gram neg curved bacilli, polar flagellum

facultatively anaerobic

51
Q

Where is V.cholerae found?

A

Marine environments

infected humans may serve as a reservoir (asymptomatic infection if infecting dose was low)

drinking water supply is main source of transmission
—-fetal oral

fresh seafood

52
Q

To cause infection of V.cholerae, how much bacteria do we need?

A

over a million

53
Q

What are the symptoms of V.cholerae ⭐️

A

Acute onset of watery stools
rice water stools
Low Fever
Little Pain

54
Q

What is the VF of V.cholerae? how does it work

A

Cholera Toxin

Increase cAMP so increase Cl- transport out of cell

Expression of cholera toxin is co-regulated with expression of pilus

55
Q

what it the fatality rate of cholera if untreated?

A

60%

56
Q

Extra fun facts of cholera

A

Convalescent carrier (asymptomatic or mild) possible

Cases in US Gulf coast states (shellfish)

Epidemic spread in many parts of world

El Tor (O1) survives longer in environment, may cause milder disease

O139 Bengal associated with more recent epidemics

57
Q

which version of V. cholerae survives longer in environment and cause milder disease

A

El Tor (O1)

58
Q

El Tor (O1) in V. cholerae

A

survives longer in environment and cause milder disease

59
Q

which version of V. cholerae is associated with more recent epidemics

A

O139 Bengal

60
Q

How is V. cholerae diagnosis?

A

Grows on blood agar
MacConkey
serotyping

61
Q

Prevention of V. cholerae

A

Oral vaccine testing by WHO, recommended for outbreak response

62
Q

What is the treatment of V. cholerae?

A

Supportive therapy (mainstay):
-IV or oral hydration with electrolyte replacement with small amounts of glucose

Antibiotics (severely ill, moderate to severe dehydration, hospitalized):
-Adults: doxycycline
-Pregnant women/children: erythromycin, azithromycin ⭐️

63
Q

How is salmonella divided?

A

S. Typhi and and S. non typhi

64
Q

What is the reservoir of S. typhi ?

A

Humans

65
Q

What is the reservoir of S. non typhi ?

A

Ubiquitous

Humans, animals, feed, eggs, dairy and water

66
Q

what is lab results of salmonella species

A

lactose neg

Motile via flagella

67
Q

What type of pathogen is Salmonella subsp. typhi

A

obligate pathogen

68
Q

what can Salmonella subsp. typhi cause

A

enteric (typhoid) fever
Septicemia

69
Q

What is the infectious dose of Salmonella subsp. typhi

A

~1000 (less than non-typhi)

70
Q

How is Salmonella subsp. typhi carried

A

Macrophages ingest & carry organisms via lymph and blood

71
Q

How is Salmonella non-typhi subsp transmitted

A

food ingestion

fecal oral

72
Q

What does Salmonella non-typhi subsp cause

A

non-blood diarrhea

73
Q

What is the infectious dose of Salmonella non-typhi subsp

A

10^6

74
Q

What it the VF and what does Salmonella non-typhi subsp do

A

Virulence
—Invasin – attachment & penetration
—Acid tolerance – protects from stomach & phagosome acids

Invade cells lining the lumen

75
Q

How do we diagnosis salmonella spp

A

differential growth on XLD agar followed by serotyping

REMEMBER: salmonella is lactose neg

76
Q

What is the treatment for salmonella

A

S.typhi: requires treatment
—–fluoroquinolones, cephalosporin, antibiotic susceptibility testing required

S. non typhi: NO ANTIBIOTICS

77
Q

What is the prevention of Salmonella

A

S.typhi vaccine: live attenuated bacterium: replicates for a short period of time

78
Q

What does shigella sp do

A

Invades colonic mucosa

79
Q

What is the timeline for shigella sp

A

1 to 3 day incubation period

Generally subsides in 10 days

80
Q

What are the VFs in shigella sp

A

Invasin
-acts on GI cells to phagocytose
-Lyse phagocytic vacuole
-Directs host cell actin (contiguous spread)

Shiga toxin
- inhibits protein synthesis
-Toxin similar to EHEC toxin
-Hemolytic uremic syndrome (HUS)

81
Q

How is shigella transmitted ?

A

human disease only (children)

Fecal oral route

82
Q

What is the infectious dose of shigella

A

<200 bacteria needed to produce infection (low)

83
Q

What does shigellosis (bacillary dysentery) cause (symptoms)

A

cramps
fever
diarrhea
tenesmus–> feeling like you need to poop but do not need to
frequent bloody
small stools

84
Q

S. dysenteriae can have a ___ mortality rate in young children

A

high

85
Q

Diagnosis of Shigellosis

A

Differential growth on XLD agar

86
Q

Treatment of shigellosis

A

Replacement of fluids & electrolytes

Generally self-limiting

Antibiotics indicated in severe cases and may shorten disease
—-Empiric treatment with ciprofloxacin but antibiotic ——-sensitivity tests should be done due to multiple drug resistant strains

Antidiarrheals contraindicated, prolong disease

87
Q

Antidirrheals are _____ and ____ ____ with shigella

A

contraindicated, prolong disease

88
Q

What is the morphology of Campylobacter jejuni

A

Gram neg bacilli, very thin, curved

Microaerophilic

Polar flagellum or flagella

89
Q

What is the reservoir for Campylobacter jejuni

A

animal

90
Q

what is the transmission of Campylobacter jejuni

A

Transmission via contaminated food, water

direct contact with carrier animals

91
Q

What is the infectious dose of Campylobacter jejuni

A

~1000

92
Q

Campylobacter jejuni is the ____ common cause of bacterial gastroenteritis in the US

A

MOST

93
Q

What is the VF of Campylobacter jejuni

A

Adhesins
Cytotoxin
Enterotoxin

Organisms multiply in the small intestine, invade the epithelium and produce inflammation (pathogen in humans)

94
Q

What are the symptoms of Campylobacter jejuni

A

abdominal cramps
fever
diarrhea with blood and leucocytes (neutrophil)
Enteritis
Bacteremia

95
Q

What causes Guillain barre syndrome

A

Campylobacter jejuni

96
Q

What is Guillain barre syndrome

A

(neuromuscular paralysis), antibodies to bacterium cross-react with antigens on neural tissue cells

97
Q

What is the diagnosis of Campylobacter jejuni

A

Selective growth on selective Campy agar to suppress growth of microflora

5-10% oxygen
42C
2-4 days incubation
Gull wing shaped cells ⭐️

98
Q

What is the treatment of Campylobacter jejuni

A

Supportive therapy
—-Fluid and electrolyte replacement

Antibiotic therapy only in severe cases:
—-Erythromycin/azithromycin
—-Ciprofloxacin
Antibiotic susceptibility testing helpful

99
Q

A 22 year old medical student took a weekend trip to Costa Rica to celebrate the end of finals for GI. The day she returns, she develops watery diarrhea, five to six times a day, with nausea, occasional vomiting, and crampy abdominal pain.
There are no leukocytes on stool exam.

a.Shigella species
b.Campylobacter jejuni
c.EHEC
d. EPEC
e.ETEC

A

E

100
Q

A family comes to your office. The father and a six-year old girl are having bloody diarrhea which started last night. The day before they ate out at a fast-food hamburger restaurant.
The little girl is dehydrated, pale and somewhat lethargic. Blood tests show that she is developing renal failure.

a.Salmonella species
b.Vibrio cholerae
c. EHEC
d. EPEC
e.ETEC

A

c.

101
Q

Your patient is a 30-year-old woman with nonbloody diarrhea
for the past 14 hours. Which one of the following organisms is
LEAST likely to cause this illness?
(A) Clostridium difficile
(B) Streptococcus pyogenes
(C) Shigella dysenteriae
(D) Salmonella enteritidis

A

b

102
Q

Which one of the following bacteria has the LOWEST 50%
infectious dose (ID50)?
(A) Shigella sonnei
(B) Vibrio cholerae
(C) Salmonella typhi
(D) Campylobacter jejuni

A

a

103
Q

For which one of the following enteric illnesses is a chronic carrier state MOST likely to develop?

(A) Campylobacter enterocolitis
(B) Shigella enterocolitis
(C) Cholera
(D) Typhoid fever

A

d

104
Q

Two hours after a delicious Thanksgiving dinner of barley soup, roast turkey, stuffing, sweet potato, green beans, cranberry sauce, and pumpkin pie topped with whipped cream, the Smith family of four experience vomiting and diarrhea. Which one of the following organisms is MOST likely to cause these symptoms?

(A) Shigella flexneri
(B) Campylobacter jejuni
(C) Staphylococcus aureus
(D) Salmonella enteritidis

A

c

105
Q

The pathogenesis of which one of the following organisms is
MOST likely to involve invasion of the intestinal mucosa?
(A) Vibrio cholerae
(B) Shigella sonnei
(C) Enterotoxigenic Escherichia coli
(D) Clostridium botulinum

A

b

106
Q

Which one of the following organisms that infects the gastrointestinal tract is the MOST frequent cause of bacteremia?

(A) Shigella flexneri
(B) Campylobacter jejuni
(C) Vibrio cholerae
(D) Salmonella typhi

A

d

107
Q

CASE: Your patient is a 50-year-old woman who returned yesterday from a vacation in Peru, where there is an epidemic of cholera. She now
has multiple episodes of diarrhea. Of the following, which one is MOST compatible with cholera?

(A) Watery diarrhea without blood, no polys in the stool, and
growth of curved gram-negative rods in the blood culture
(B) Watery diarrhea without blood, no polys in the stool, and no organisms in the blood culture
(C) Bloody diarrhea, polys in the stool, and growth of curved
gram-negative rods in the blood culture
(D) Bloody diarrhea, polys in the stool, and no organisms in the
blood culture

A

b

108
Q

Your patient is a 5-year-old girl with bloody diarrhea and no
vomiting. There is no history of travel outside of San Francisco. Stool culture grows both lactose-positive and lactose-negative colonies on EMB agar. Of the following organisms, which one is MOST likely to be the
cause?
(A) Shigella sonnei
(B) Salmonella typhi
(C) Campylobacter jejuni
(D) Helicobacter pylori

A

a

109
Q

CASE: Your patient is a 40-year-old woman with a severe attack of diarrhea that began on the airplane while she was returning from a vacation in the Middle East. She had had multiple episodes of watery, nonbloody diarrhea and little vomiting. She is afebrile. A stool culture
reveals only lactose-fermenting colonies on EMB agar. Of the following, which one is the MOST likely cause?

(A) Shigella sonnei
(B) Helicobacter pylori
(C) Escherichia coli
(D) Pseudomonas aeruginosa

A

c

110
Q

CASE: Your patient is a 30-year-old woman who was part of a tour group visiting a Central American country. The day before leaving, several members of the group developed fever, abdominal cramps, and bloody diarrhea. Of the following, which one is the LEAST likely organism to cause this infection?

(A) Shigella dysenteriae
(B) Salmonella enteritidis
(C) Vibrio cholerae
(D) Campylobacter jejuni

A

c

111
Q

CASE: Your patient is a 30-year-old woman who was part of a tour group visiting a Central American country. The day before leaving, several members of the group developed fever, abdominal cramps, and bloody diarrhea. Of the following, which one is the LEAST likely organism to cause this infection
UPDATE: A stool culture reveals no lactose-negative colonies on the EMB agar. Which one of the following is the MOST likely organism to cause this infection?

(A) Shigella dysenteriae
(B) Salmonella enteritidis
(C) Vibrio cholerae
(D) Campylobacter jejuni

A

d

Microbiology (18 decks)

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