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NBME Micro > Bacteria: Gram Negative Bacilli - Enteric Tract > Flashcards

Bacteria: Gram Negative Bacilli - Enteric Tract Flashcards

1
Q

List the gram negative bacilli in the enteric tract

A
  1. Klebsiella Pnuemoniae
  2. Enterobacter spp
  3. Serratia Marcescens
  4. Salmonella Enteritidis
  5. Salmonella Typhi
  6. Shigella
  7. Escherichia Coli
  8. Yersinia Enterocoliticia
  9. Yersinia Pestis
  10. Camplyobacter Jejuni
  11. Vibrio Spp
  12. Helicobacter pylori
  13. Pseudomonas Aeruginosa
  14. Proteus Mirabilis
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2
Q

Enterobacter spp., Serratia marcescens, and Klebsiella pneumoniae bacteria

A
  1. gram-negative bacillus
  2. can cause pneumonia
  3. are common causes of UTIs
  4. are common nosocomial pathogens
  5. commonly exhibit multi drug resistance
  6. lactose fermenting bacteria
  7. form pink colonies on MacConkey agar
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3
Q

Enterobacter spp

A
  1. motile
  2. gram negative
  3. bacillus
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4
Q

Serratia marcescens

A
  1. gram negative
  2. bacillus
  3. motile
  4. produce a distinct red pigment
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5
Q

Klebsiella pneumoniae is common in

A

alcoholics, leads to abscesses, and often causes aspiration pneumonia

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6
Q

Klebsiella pneumoniae bacterial cells are surrounded by

A

a prominent polysaccharide capsule

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7
Q

The sputum produced by patients with Klebsiella pneumoniae is classically described as

A

“currant jelly sputum”

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8
Q

Klebsiella pneumoniae bacteria are

A
  1. gram negative
  2. bacillus
  3. immotile
  4. urease positive
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9
Q

Serratia marcescens produces a

A

distinct red pigment

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10
Q

Cavitary lesions resembling those in tuberculosis may develop in

A

Klebsiella pneumoniae pulmonary infections

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11
Q

Salmonella

A
  1. gram negative
  2. bacilli
  3. motile
  4. form black colonies on Hektoen enteric agar (HE) due to production of H2S (differentiating them from Shigella spp., which form green colonies on HE)
  5. encapsulated
  6. acid labile
  7. can cause osteomyelitis in sickle cell patients
  8. facultative intracellular within macrophages
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12
Q

Salmonella enteritidis and typhi bacteria form

A

black colonies on Hektoen enteric agar (HE) due to production of H2S (differentiating them from Shigella spp., which form green colonies on HE)

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13
Q

Chickens are the reservoir for

A

Salmonella enteritidis

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14
Q

Salmonella typhi colonizes

A

the gallbladder of chronic carriers

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15
Q

Typhoid fever

A
  1. caused by Salmonella typhi bacteria
  2. can present with a characteristic rash known as “rose spots”
  3. the khaki-green stools seen in typhoid fever are sometimes referred to as “pea soup” stools
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16
Q

Treatment for salmonella

A

fluoroquinolones are effective against Salmonella typhi (infections caused by Salmonella enteritidis typically do not require antibiotic therapy)

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17
Q

Vaccination for Salmonella typhi

A

a vaccination is available for Salmonella typhi only (the oral vaccine contains live attenuated Salmonella typhi, and the intramuscular vaccine includes a Salmonella typhi capsular antigen)

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18
Q

Salmonella enteritidis (and other nontyphoidal serotypes) most commonly cause

A

a self-limited gastroenteritis

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19
Q

Salmonella enteritidis and typhi bacteria possess

A

a type III secretion system that delivers effector proteins directly into host cells

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20
Q

Shigella

A
  1. gram negative
  2. bacilli
  3. immotile
  4. acid-resistant (a low inoculum is required to cause infection)
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21
Q

Shigella spp. bacteria form

A

green colonies on Hektoen enteric agar (HE) (differentiating them from Salmonella spp., which form black colonies on HE)

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22
Q

Shigella spp. invade

A

M cells in Peyer’s patches of the gastrointestinal mucosa (where they induce host cell apoptosis and manipulate actin filaments of the eukaryotic cytoskeleton to achieve intracellular motility)

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23
Q

Shigella spp. can

A

manipulate the eukaryotic cytoskeleton (primarily actin filaments) to achieve intracellular motility after invading M cells in Peyer’s patches of the gastrointestinal mucos

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24
Q

bloody diarrhea is a common symptom of

A

shigellosis

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25
Q

Shigellosis

A
  1. shigellosis can lead to gastroenteritis and diarrhea, characterized by the presence of leukocytes (predominantly neutrophils) in the stool
  2. bloody diarrhea is a common symptom
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26
Q

Shiga Toxin

A

Shiga toxin produced by Shigella dysenteriae can cause hemolytic uremic syndrome (HUS) due to cytotoxic effects on endothelial cells of the capillaries in glomeruli (leading to platelet adherence and aggregation → thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury)

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27
Q

Microangiopathic hemolytic anemia (MAHA) often presents with

A

schistocytes in peripheral blood smear and is a component of hemolytic uremic syndrome (HUS) (caused by Shiga toxin producing strains of bacteria, such as Shigella dysenteriae)

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28
Q

Platelet adherence and aggregation in hemolytic uremic syndrome (HUS)

A

platelet adherence and aggregation in hemolytic uremic syndrome (HUS) (caused by Shiga toxin producing strains of bacteria, such as Shigella dysenteriae) occurs due to cytotoxic effects on endothelial cells of the capillaries in the glomerulus → thrombocytopenia, microangiopathic hemolytic anemia, and renal insufficiency

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29
Q

Young children are more commonly affected by

A

hemolytic uremic syndrome (HUS), which is caused by Shiga toxin producing strains of bacteria, such as Shigella dysenteriae

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30
Q

Shigella dysenteriae

A

produces Shiga toxin (virtually identical to the Shiga-like toxin of enterohemorrhagic E. coli) which inactivates the 60S ribosomal subunit

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31
Q

Shigella spp. bacteria possess

A

a type III secretion system that delivers effector proteins directly into host cells

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32
Q

E. coli

A
  1. gram-negative
  2. bacillus
  3. lactose fermenting
  4. form pink colonies on MacConkey agar
  5. encapsulated
  6. catalase positive
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33
Q

The K antigen of E. Coli is a

A

polysaccharide capsular antigen

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34
Q

E. coli bacteria form

A

characteristic metallic green colonies on eosin methylene blue (EMB) agar

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35
Q

The fimbriae of E. coli permit

A

adhesion to host cells

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36
Q

E. coli is the most common cause of

A
  1. urinary tract infections

2. gram negative sepsis

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37
Q

Only E. coli strains that possess the K1 capsular antigen cause

A

neonatal meningitis

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38
Q

Enterohemorrhagic E. coli (EHEC) is transmitted via

A

contaminated undercooked meat

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39
Q

Enterohemorrhagic E. coli (EHEC) can cause

A

bloody diarrhea

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40
Q

Escherichia coli O157:H7 can be differentiated from other strains of E. coli by

A

its inability to ferment sorbitol

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41
Q

Enterohemorrhagic E. coli (EHEC) produces a

A

Shiga-like toxin (virtually identical to the Shiga toxin of Shigella dysenteriae) which inactivates the 60S ribosomal subunit in host cells

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42
Q

Shiga-like toxin

A

(virtually identical to the Shiga toxin of Shigella dysenteriae) which inactivates the 60S ribosomal subunit in host cells

43
Q

Platelet adherence and aggregation in hemolytic uremic syndrome (HUS) (caused by Shiga-like toxin producing bacteria, such as some strains of E. coli) occurs due to

A

cytotoxic effects on endothelial cells of the capillaries in the glomerulus → thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury

44
Q

Escherichia coli O157:H7 is an

A

enterohemorrhagic E. coli serotype that produces Shiga-like toxin, which can cause bloody diarrhea and hemolytic uremic syndrome (HUS)

45
Q

Enterotoxigenic E. coli (ETEC) is a common cause of

A

“traveler’s diarrhea,” which often presents with watery diarrhea, abdominal cramping, nausea, and vomiting

46
Q

Some strains of enterotoxigenic E. coli (ETEC) produce

A
  1. heat-labile toxin (LT), which overactivates adenylyl cyclase → increased cAMP → water and chloride efflux with decreased sodium reabsorption, resulting in watery diarrhea (secretory diarrhea)
  2. heat-stable toxin (ST), which overactivates guanylate cyclase → increased cGMP → decreased reabsorption of sodium and chloride, resulting in watery diarrhea (secretory diarrhea)
47
Q

Enterotoxigenic E. coli (ETEC) is a common cause of “traveler’s diarrhea,” which often presents with

A

watery diarrhea, abdominal cramping, nausea, and vomiting

48
Q

Yersinia enterocolitica

A
  1. gram negative
  2. bacillus
  3. Primarily transmitted via pet feces
  4. outbreaks are associated with daycare centers
  5. can be transmitted via contaminated milk and dairy products
49
Q

Yersinia Pestis

A
  1. gram negative

2. bacillus

50
Q

25°C is the optimal temperature for growth of

A

Yersinia enterocolitica bacteria (in contrast to Yersinia pestis, which is cultured most rapidly at 30°C)

51
Q

Yersinia pestis and enterocolitica bacteria

A
  1. often exhibit bipolar (“safety pin”) staining on microscopy
  2. encapsulated
52
Q

Yersinia enterocolitica infection can cause

A

bloody diarrhea

53
Q

Yersinia enterocolitica infection can mimic

A

appendicitis (pseudoappendicitis)

54
Q

rodents, such as rats and prairie dogs, are the main reservoir for

A

Yersinia pestis

55
Q

fleas are the vector of

A

Yersinia pestis bacteria

56
Q

intensely painful and swollen lymph nodes with overlying erythema (buboes) are characteristic of

A

Yersinia pestis infection

57
Q

Disseminated Yersinia pestis infection can lead to

A

tissue necrosis and cutaneous hemorrhage, DIC, septic shock, and multiple organ dysfunction syndrome

58
Q

Yersinia spp. bacteria possess

A

a type III secretion system that delivers effector proteins directly into host cells, such as Yersinia outer proteins (Yops)

59
Q

_______ are effective against Yersinia spp.

A
  1. aminoglycosides (particularly streptomycin)

2. tetracyclines

60
Q

An inactivated (killed) vaccine against Yersinia pestis is

A

available, though not routinely administered in the US

61
Q

Campylobacter jejuni

A
  1. gram-negative
  2. curved bacillus
  3. thermophilic bacteria
  4. grows at 42°C
  5. oxidase positive
62
Q

animals such as poultry, cattle, sheep, and dogs are common reservoirs for

A

Campylobacter jejuni

63
Q

Campylobacter jejuniinfection can cause

A

bloody diarrhea

64
Q

C. jejuni has a characteristic

A

“seagull wing” shape on microscopy

65
Q

Campylobacter jejuni is an invasive pathogen and is able to

A

penetrate the intestinal epithelium, frequently leading to bloody diarrhea

66
Q

Campylobacter jejuni infection is associated with

A

reactive arthritis

67
Q

Guillain-Barre syndrome

A

can develop after a Campylobacter jejuni infection (characterized by progressive bilateral ascending weakness and loss of reflexes)

68
Q

Vibrio cholerae

A
  1. gram-negative
  2. curved bacillus
  3. comma shaped bacilli
69
Q

Cholera is endemic to

A

developing countries (outbreaks occur most commonly in southern Asia, Latin America, and Africa)

70
Q

Vibrio cholerae can cause

A

profuse watery diarrhea, commonly referred to as “rice-water stool”

71
Q

Transmission of Vibrio cholerae is

A

fecal-oral

72
Q

The fimbriae of Vibrio cholerae

A

allow the bacteria to attach to (but do not invade) the intestinal mucosa and establish infection

73
Q

Cholera toxin (choleragen) of Vibrio cholerae

A

activates adenylate cyclase in epithelial cells of the intestine → elevated cAMP, increased sodium and chloride efflux → profuse watery diarrhea (secretory diarrhea)

74
Q

Cholera toxin permanently activates

A

Gs → overactivation of adenylate cyclase → elevated cAMP, increased sodium and chloride efflux → profuse watery diarrhea (secretory diarrhea)

75
Q

Oral rehydration is the primary treatment of

A

cholera

76
Q

Vibrio spp. bacteria preferentially grow in

A

alkaline media

77
Q

Vibrio spp. bacteria are

A
  1. extremely acid-labile, and a high number of ingested organisms are required to cause infection
  2. oxidase positive
78
Q

Vibrio parahaemolyticus and vulnificus infections are associated with

A

consumption of raw oysters

79
Q

Helicobacter pylori is

A
  1. gram-negative
  2. curved bacillus
  3. motile
  4. urease positive
  5. oxidase positive
80
Q

H. pylori’s ability to convert urea to ammonia and carbon dioxide is the basis of

A

the urea breath test

81
Q

the development of gastric and duodenal ulcers is strongly associated with

A

Helicobacter pylori infection

82
Q

Helicobacter pylori infection significantly increases the risk of developing

A

gastric adenocarcinoma

83
Q

gastric mucosa-associated lymphoid tissue lymphomas (MALTomas) is associated with

A

Helicobacter pylori infection

84
Q

Treatment of H. Pylori

A
  1. proton pump inhibitors are used in conjunction with clarithromycin and amoxicillin/metronidazole (triple therapy)
85
Q

~90% of duodenal ulcers are associated with

A

Helicobacter pylori

86
Q

Pseudomonas aeruginosa

A
  1. gram-negative
  2. bacillus
  3. thrives in aquatic environments
  4. oxidase positive
  5. catalase positive
  6. obligate aerobic pathogens
  7. encapsulated
  8. motile (Swarming motility)
87
Q

Pseudomonas aeruginosa produces a

A
  1. characteristic blue-green pigment (pyocyanin and pyoverdin)
  2. a fruity grape-like odor when plated
88
Q

Pseudomonas aeruginosa is a common cause of

A

nosocomial infections

89
Q

Pseudomonas aeruginosa is a major cause of

A

lung infection and respiratory failure in cystic fibrosis patients

90
Q

diabetics and IV drug users are at a higher risk of

A

Pseudomonas osteomyelitis

91
Q

burn patients are at a higher risk of

A

Pseudomonas aeruginosa wound infections

92
Q

Pseudomonas aeruginosa is associated with

A

indwelling catheters and is a common cause of nosocomial UTIs

93
Q

Pseudomonas aeruginosa can cause a

A
  1. superficial infection of the hair follicle (characterized by a pruritic papulopustular rash) known as “hot tub folliculitis”
  2. otitis externa, or infections of the outer ear (also known as “swimmer’s ear”)
94
Q

Pseudomonas aeruginosa sepsis can lead to

A

ecthyma gangrenosum, a rare cutaneous disease that presents with black, necrotic lesions

95
Q

exotoxin A of Pseudomonas aeruginosa

A

inhibits elongation factor-2 by ADP ribosylation (a mechanism similar to that of diphtheria toxin)

96
Q

the antipseudomonal antibiotics piperacillin and ticarcillin are effective against

A

Pseudomonas aeruginosa

97
Q

fluoroquinolones can be used to treat

A

Pseudomonas aeruginosa infection

98
Q

aminoglycosides can be combined with beta-lactam antibiotics to treat

A

Pseudomonas aeruginosa infection

99
Q

Proteus mirabilis

A
  1. gram-negative
  2. bacillus
  3. swarming motility when plated
  4. urease positive
100
Q

staghorn calculi (struvite stones composed of magnesium ammonium phosphate) are sometimes seen in cases of

A

urinary tract infection with urease-positive pathogens, such as Proteus mirabilis

101
Q

struvite stones

A

precipitate in alkaline urine (the hydrolyzation of urea to ammonia by urease-positive organisms, such as Proteus mirabilis, increases urine pH to a neutral or alkaline level)

102
Q

Proteus mirabilis causes

A

UTIs

103
Q

Proteus mirabilis produces a

A

characteristic fishy odor

104
Q

_____ are effective against Proteus mirabilis

A

sulfonamides

NBME Micro (36 decks)

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