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Step 1 - Microbiology > Gram Negative Bacteria > Flashcards

Gram Negative Bacteria Flashcards

1
Q

Neisseria - Overview

Gram Negative Diplococci

A
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2
Q

Neisseria gonorrheae

A
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3
Q

Neisseria meningitidis

A
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4
Q

People with terminal complement deficiency (c5-c9) are particularly susceptible to which type of gram negative infection?

A

Neisseria infections.

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5
Q

Antigenic variation of what in Neisseria infections?

A

Pili
* Hair-like proteins that facilitate attachment to mucosal surfaces

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6
Q

Concerning Neisseria complication (as a class, overall)?

A

Disseminated intravascular coagulopathy (DIC)– causing petechial skin rash.

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7
Q

Liver pain in a young woman who otherwise has an STD:

A

Fitz-Hugh-Curtis syndrome
* Perihepatitis – infection & inflammation of the liver
* Violin-string adhesions of the peritoneum to the liver

Complication of PID.

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8
Q

Necessary co-treatment of gonococcal & chlamydia infections:

A

Gonorrhea
* Ceftriaxone IM injection

Chlamydia
* Azithromycin (macrolides)
* Doxycyclines (tetracyclines)

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9
Q

Haemophilus influenzae

A
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10
Q

Bordetella pertussis

A
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11
Q

H. Flu can be co-cultured with which other organism?

A

Staph Aureus (which provides factor 5 through the breakdown of RBCs).
* Factor 5 (NAD+)
* Factor 10 (hematin)

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12
Q

Which organ is mainly responsible for filtering encapsulated bacteria from the blood?

A

Spleen

  • This is why asplenic patients are particularly susceptible to infections caused by encapsulated organisms:
  1. H. flu
  2. N. meningitidis
  3. Strep pneumo
  4. Pseudomonas aeruginosa
  5. E. coli
  6. Salmonella
  7. Klebsiella
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13
Q

Epiglottitis (inspiratory stridor) & a patient in tripod position is likely affected with which organism?

A

H. Flu (type B)

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14
Q

Medication indications for different H. Flu complications:

A

Sinusitus, otitis media (mucosal resp/airway infections)
* Amoxicillin clavulanate

Meningitis
* Ceftriaxone (IM)

Prophylaxis for close contacts
* Rifampin

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15
Q

Organisms that produce culture-negative endocarditis:

A

HACEK

  1. Haemophilus
  2. Actinobacillus
  3. Cardiobacter
  4. Eikenella
  5. Kingella
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16
Q

Pertussis toxin does what?

A
  • activates adenylate cyclase by inhibiting Gi
  • increasing cAMP
  • increased permeability of the cell membrane
  • flow of ions and fluid out of the cell into the extracellular space
  • EDEMA
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17
Q

3 phases of whooping cough:

A
  1. Catarrhal phase – low grade fevers and runny nose
  2. Paroxysmal – intense cough with inspiratory whooop. Can be so severe that the coughs cause vomiting (posttussive emesis)
  3. Convalesecent – gradual recovery of bronchitis & cough
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18
Q

Why could bordetella pertussis be mistaken for a viral infection?

A

Because of the lymphocytic infiltrate resulting from immune response.

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19
Q

Gram negative bacteria what color under the microscope (after gram stain)?

A
  • Red
  • Pink
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20
Q

Brucella

A
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21
Q

Rx combination to treat Brucella

A

Doxycycline & Rifampin.

  • Transmitted through the ingestion of contaminated animal products.
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22
Q

Name that organism: Long time smoker with chronic lung disease who is presenting with severe unilateral lobar pneumonia, high fever, CNS symptoms, GI symptoms, and hyponatremia – and many other people on the same cruise ship are affected:

A

Legionella (gram negative rod)

  • Causing Legionnaires’ disease (shared water source)
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23
Q

Why is Legionella so hard to visualize?

A

Because it’s mainly intracellular (facultative).

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24
Q

Hyponatremia will lead to what cardiac finding on physical exam?

A

Bradycardia

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25
Q

If a patient has both diarrhea (GI symptoms) and coughing (lung symptoms), think of this gram negative bacillus:

A

Legionella pneumophila

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26
Q

How to Dx Legionella?

A

Urine antigen test.

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27
Q

Legionella pneumophila

A
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28
Q

Pseudomonas aeruginosa (characteristics)

A
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29
Q

Pseudomonas aeruginosa (virulence factors)

A
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30
Q

Name the offending organism: Hot tub folliculitis & malignant otitis externa

A

Pseudomonas aeruginosa

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31
Q

The 4 risk factors for Pseudomonas Aeruginosa:

Warm, moist environments

A
  1. Hot tubs/pools
  2. Cystic Fibrosis
  3. Ecthyma gangrenosum (immunocompromised patients)
  4. Indwelling (foley) catheter – causes UTIs

Common nosocomial infection.

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32
Q

Which 3rd generation cephalosporin is not effective for pseudomonas aeruginosa?

A
  • Ceftriaxone
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33
Q

Rx that is effective for pseudomonas aeruginosa?

A

1st Line
1. Piperacillin, Ticarcillin
2. Ceftazidime (3rd gen), Cefepime (4th gen)

Next – acquired resistance
1. Fluoroquinolones (cipro, levo)
2. Carbapenems (mero, imi)

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34
Q

Pseudomonas aeruginosa (disease)

A
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35
Q

Salmonella (overview)

A
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36
Q

How to distinguish salmonella and shigella (both being gram negative rods that are oxidase-negative and don’t ferment lactose)?

A

Hydrogen Sulfide test

  • Only Salmonella produces H2S & black precipitate on iron agar?

Motility test
* Salmonella is motile
* Shigella is non-motile

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37
Q

Is salmonella acid-stable or acid-labile?

A

Acid-labile. It requires a high infectious dose to cause disease.

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38
Q

How does Salmonella invade the GI Tract (same as Shigella)?

A

It invades the M-cells of the Peyer’s Patches in the intestines (collections of lymphoid tissue that assess for infection)

  • After it moves past the intestinal wall, it travels through the mesenteric lymph nodes – where it multiplies inside macrophages
  • Macrophages are lysed and released
39
Q

Salmonella typhi

40
Q

High yield clinical association between S. typhi & sickle cell patients?

A

Development of osteomyelitis.

41
Q

How would you describe the diarrhea in S. typhi versus Shigella?

A

S. typhi
* Pea-soup watery diarrhea

Shigella
* Bloody mucoid diarrhea (inflammatory)

42
Q

Salmonella enteritidis

43
Q

Shigella

44
Q

What is the 1st line Rx for S. typhi?

A

Fluoroquinolones

2nd line
* Azithromycin (macrolides)

45
Q

Which population group is most affected by Shigella?

A

Children
* Adults have better immunity to fight off Shigella infection

46
Q

What is the main cause of Shigella’s pathogenicity?

A

Direct bacterial spread.
* Not toxin-mediated (despite the production of Shiga toxin– which is more important with E. coli’s Shiga-like toxin)

47
Q

Yersinia enterocolitica

48
Q

How does Yersinia’s enterotoxin work?

A
  1. It actives guanylate cyclase
  2. Increases intracellular levels of cGMP
  3. Results in watery diarrhea
49
Q

E. coli (overview)

50
Q

What is one of the unique biochemical characteristics of E. coli bacteria that can be assessed in the lab?

A

It is Indole (+). Can break tryptophan down into Indole.

  • It is also Lactose-fermenting (& glucose-fermenting) on EMB agar (blue color)
51
Q

Which E. coli virulence factor is implicated in neonatal meningitis?

A

K1 polysaccharide capsule
* Prevents phagocytosis or complement activation

52
Q

Which E. coli virulence factor is implicated in UTIs?

A

Pili / Fimbriae
* Enables adhesion to the uroepithelial surface

53
Q

ETEC vs. EHEC diarrhea:

A

ETEC
* Watery diarrhea

EHEC
* Bloody diarrhea

54
Q

Name that bug: Common cause of acute kidney failure in otherwise healthy patients in the USA. Patient has quickly developed bloody diarrhea and worsened kidney function after an outdoor BBQ

A

EHEC 0157:H7

  • Hemolytic-uremic syndrome (HUS)
55
Q

Clinical triad of Hemolytic-uremic syndrome in EHEC:

A

Triad
1. Hemolytic anemia
2. Thrombocytopenia
3. AKI

56
Q

What is the major mediator of pathogenicity in EHEC 0157:H7?

A

Shiga-like toxin

  • Inactivates the 60s ribosomal subunit
  • stops protein production – leads to cell death
  • Toxin-mediated enterocyte death & intestinal hemorrhage
  • (In contrast to Shigella, where toxin plays a minor role in pathogenesis)
57
Q

EHEC 0157:H7

59
Q

2 enterotoxins in ETEC:

A
  1. LT – increases cAMP in gut mucosa (like cholera toxin)
  2. ST – increases cGMP in gut mucosa

Result = watery diarrhea

60
Q

Gram negative rod that is both:
1. Lactose-fermenting
2. Urease positive

A

High clinical suspicion for Klebsiella pneumoniae

61
Q

Klebsiella pneumoniae commonly causes which type of pneumonia?

A

Aspiration pneumonia (usually lobar).

  • Elderly
  • Alcoholics
  • Diabetics
62
Q

Which gram negative bacteria can lead to to struvite kidney stones?

A

Klebsiella pneumoniae

63
Q

Klebsiella pneumoniae

64
Q

All gram-negative curved rods have what biochemical trait?

A

They are oxidase-positive.

65
Q

Which gram negative corkscrew-shaped rod bacteria grows specificlaly at 42 degrees celsius?

A

Campylobacter jejuni

66
Q

Campylobacter jejuni

67
Q

Vibrio (Cholera)

68
Q

Helicobacter Pylori

69
Q

Borrelia burgdoferi (Lyme)

70
Q

Leptospira Interrogans

71
Q

What gram negative spirochete infection are people who do a lot of water sports most susceptible to?

Hint: presents with conjunctival suffusion, liver failure, and renal failure

A

Leptospirosis

72
Q

Name that syndrome: Patient exhibits ascending muscle weakness after having bloody diarrhea

A

Guillain-Barre syndrome after C. Jejuni infection

73
Q

Name that bug: Patient exhibits unilateral arthritis of the knee, conjunctivitis, & urethritis

A

Campylobacter jejuni

Reactive arthritis triad
1. Unilateral arthritis of large joints (knee)
2. Conjunctivitis
3. Urethritis

74
Q

Biochemical profile of Vibrio cholerae:

A
  1. Oxidase (+)
  2. Alkaline media (TCBS agar growth)
  3. Motile - flagella
  4. Gram-negative comma shaped rod
75
Q

Ingestion of contaminated shellfish in the USA can result in which gram-negative comma shaped rod infection?

A

Vibrio cholerae

76
Q

Diarrhea description for Vibrio cholerae:

A

Rice-water diarrhea

77
Q

Name that bug: Patient who lives in New England is exhibiting heart (AV) block), facial dropping, and migratory joint pains

A

Borrelia burdgorferi (Lyme disease)

Rx = Doxycycline

78
Q

Treponema pallidum (overview - part 1)

79
Q

Treponema pallidum (overview - part 2)

80
Q

Treponema pallidum (Dx)

81
Q

Congenital Syphilis

82
Q

Chlamydia (overview)

83
Q

Which form of chlamydia is infectious: elementary body or reticular body?

A

Elementary body.

  1. Elementary body – extracellular infectious form
  2. Reticular body – intracellular replicating form (large inclusion body) that releases elementary bodies
84
Q

Name that organism: “Can’t see, can’t pee, can’t climb a tree”

A

Chlamydia trachomatis

85
Q

Chlamydia trachomatis

86
Q

Chlamydia pneumoniae vs. psittaci

87
Q

Rx for Chlamydia pneumoniae vs. psittaci

The Psittaci parrot loves Doxy.

A

C. pneumoniae – Azithromyrin (macrolides)

C. psittaci – Doxycycline

88
Q

Rickettsia rickettsii

89
Q

Direction of rash spread in the Rickettsia family: rickettsii vs. typhi & prowazekii

A

Rickettsii in Rocky Mountain Spotted Fever
* Centripetal behavior
* Starts at the palms & soles / wrists & ankles – then moves inward to the trunk

Typhi & Prowazekii
* Rash on the trunk (centrally) that spreads outward, and spares the palms and soles

90
Q

Rickettsia typhi vs. prowazekii

The poacher has body lice & the tiger has (rat) fleas.

91
Q

Anaplasma vs. Ehrlichia (overview)

92
Q

What clinical presentation can help you distinguish between Anaplasma (ixodes tick) & Ehrlichia (lone star tick), as they both cause non-specific flu-like illness?

A

Ehrlichia causes a rash, whereas Anaplasma doesn’t.

93
Q

Anaplasma vs. Ehrlichia: vector & infected cell types

A

Anaplasma
* Ixodes tick
* Infects PMN

Ehrlichia
* Lone Star tick
* infects monocytes (macrophages)

Both show mulberry-like inclusions in cytoplasm.

94
Q

Coxiella burnetii (Q fever)

Step 1 - Microbiology (10 decks)

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