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USMLE Step 1 > Microbiology: Bacterial > Flashcards

Microbiology: Bacterial Flashcards

1
Q

Two toxins produced by C. difficile:

What kind of toxin? What is its function?

A

Toxin A = enterotoxin = exotoxin, binds brush border.

Toxin B = cytotoxin = destroys enterocyte cytoskeleton -> pseudomembranous colitis.

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2
Q

Two antibiotics especially associated with C. diff:

A

Clinda

Amp

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3
Q

Treatment for C. diff:

A

Metronidazole

ORAL vanc

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4
Q

Dx of C. diff:

A

Toxin in stool

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5
Q

Most common E. coli strain causing bloody diarrhea:

A

Enteroinvasive

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6
Q

Treatment for dysentery caused by E. coli:

A

Fluoroquinolones, TMP-SMX

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7
Q

Two toxins produced by enterotoxigenic E. coli:

Second messenger inside the cell for action of each?

A

Heat labile = cAMP increase = watery diarrhea like cholera

Heat stable = cGMP increase

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8
Q

Cause of traveler’s diarrhea (“Montezuma’s revenge”):

A

Enterotoxigenic E. coli

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9
Q

E. coli strain causing diarrhea in daycare:

A

EPEC

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10
Q

Causes HUS:

A

Enterohemorrhagic E. coli

Usually 0157:H7

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11
Q

Triad of HUS:

Explain how this happens:

A

Anemia
Thrombocytopenia
Acute renal failure
Shiga-like toxin from EHEC 0157:H7 damages endothelium, which swells, cuts off blood flow to the kidney. Narrow vessels shear RBC -> mechanical hemolysis. Damaged endothelium consumes the platelets -> thrombocytopenia.

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12
Q

Most E. coli ferment this sugar:

Which one does not?

A

Sorbitol

EHEC does not ferment sorbitol

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13
Q

Tx for HUS:

A

Supportive only.

Do not give abx.

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14
Q

Two E. coli strains causing dysentery:

A

Enteroinvasive

Enterohemorrhagic

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15
Q

E. coli strain causing watery diarrhea:

A

Enterotoxigenic

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16
Q

How would you distinguish EHEC from other forms of E. coli on culture?

A

It does not ferment sorbitol. The others do.

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17
Q

Organism responsible for causing staghorn calculi:

A

Proteus

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18
Q

Urease-positive, ammonium-Mg-phosphate stones:

A

Proteus

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19
Q

Common cause of osteomyelitis in sickle cell patients:

A

Salmonella

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20
Q

Four A’s of Klebsiella:

A

Aspiration pneumonia
Alcoholics
Abscesses in lungs and liver
di-A-betics

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21
Q

Mucoid colonies, lobar pneumonia in a diabetic:

A

Klebsiella

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22
Q

Flagellated organism, hematogenous dissemination, produces H2S:

A

Salmonella

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23
Q

Very virulent organism, frequently causes bloody diarrhea, human and primate but not pet reservoirs:

A

Shigella

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24
Q

Associated with Reiter syndrome:

A

Shigella

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25
Q

Rose spots on abdomen:

A

Salmonella typhi

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26
Q

Carried in the gallbladder, found only in humans:

A

Salmonella typhi

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27
Q

Which organism ferments lactose: Salmonella or Shigella?

A

Trick question.

Neither.

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28
Q

Which organism produces H2S: Salmonella or shigella?

A

Salmonella

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29
Q

Which organism produces a monocytic response: Salmonella or Shigella? A PMN response?

A 
Monocytes = Salmonella
PMNs = Shigella
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30
Q

Leading cause of bloody diarrhea in the US:

A

Campylobacter

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31
Q

Common antecedent to Guillain-Barre:

A

Campylobacter

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32
Q

Fecal-oral transmission through poultry, meat, milk, grows at 42C:

A

Campylobacter

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33
Q

Oxidase (+), grows in alkaline media:

A

Vibrio cholerae

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34
Q

Mesenteric adenitis that can look like Chron’s, pet feces:

A

Yersinia enterocolitica

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35
Q

Egg salad -> delayed diarrhea:

A

Salmonella

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36
Q

Egg salad -> instant diarrhea / vomiting:

A

S. aureus

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37
Q

Permanently activates Gs, toxin is heat-stable:

A

Vibrio cholerae

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38
Q

Food poisoning from contaminated seafood:

A

Vibrio sp.

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39
Q

Food poisoning from reheated rice:

A

Bacillus cereus

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40
Q

Preformed toxin, food poisoning from custard:

A

S. aureus

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41
Q

Food poisoning from reheated meat:

A

Clostridium perfringens

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42
Q

Undercooked meat, bloody diarrhea:

A

E. coli 0157:H7

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43
Q

Infection with these three organisms can mimic appendicitis:

A

Yersinia enterocolitica
Salmonella
Campylobacter

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44
Q

Most common cause of mesenteric adenitis:

A

Yersinia

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45
Q

Food poisoning as a result of mayonnaise sitting out:

A

S. aureus

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46
Q

Diarrhea caused by a gram (-) non-motile non-lactose fermenting organism:

A

Shigella

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47
Q

Rice-water stools (2):

A

V. cholera

ETEC

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48
Q

Diarrhea caused by an S-shaped organism:

A

Campylobacter

Remember, campy=twisted, it’s more of a corkscrew than a comma, but they might say “S-shaped”

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49
Q

Diarrhea caused by a non-lactose fermenting Gram (-) motile organism:

A

Salmonella

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50
Q

Diarrhea caused by a Gram (-) lactose fermenting bacterium:

A non-lactose-fermenting bacterium:

A

E. coli

Salmonella or Shigella

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51
Q

Cause of Chagas disease?

Cause of African sleeping sickness?

A

Trypanosoma cruzii

Trypanosoma brucei, gambiense, or rhodesiense

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52
Q

This form of the malaria parasite looks like a diamond ring inside an RBC:

A

Trophozoite

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53
Q

This form of the malaria parasite is the one that ruptures the RBC:

A

Merozoite

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54
Q

This form of the malaria parasite replicates inside RBCs:

A

Schizont

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55
Q

This is the form of the malaria parasite injected by the Anopheles mosquito:

A

Sporozoite

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56
Q

This form of the malaria parasite is banana-shaped:

A

Gametocyte

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57
Q

Describe how Shigella gains access to the intestinal mucosa:

A

Via M cells in Peyer’s patches, through endocytosis. It spreads laterally from M cells to other epithelial cells.

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58
Q

The _________ is where you will find b-lactamase.

A

Periplasm

This is in Gram (-)s

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59
Q

This bacterial structure protects against phagocytosis:

A

Capsule

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60
Q

This bacterium is encapsulated, but its capsule is not polysaccharide like the others. What is it, and what is its capsule made of?

A

Bacillus

Capsule contains D-glutamate

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61
Q

What is the test for whether a bacterium is encapsulated or not?

A

Quellung reaction

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62
Q

This structure mediates adherence to surfaces:

This structure mediates adherence to cells:

A

Glycocalyx makes biofilms

Pilus is a glycoprotein projection that mediates cell-cell interactions

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63
Q 
Feature of Gram (+) bacterial cell walls not shared with Gram (-)s:
What cytokines (2) does this cell wall component prompt release of?
A

Lipoteichoic acid

This induces IL-1 and TNF-a production

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64
Q

Two structural features of Gram (-) bacteria not shared with Gram (+)s:

A

Endotoxin / LPS outer membrane

Periplasmic space

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65
Q

What is unusual about Mycoplasma’s cell wall and membrane?

A
  1. It has no cell wall

2. Membrane contains a lot of sterols

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66
Q

What is unusual about the cell walls of the Mycobacteria?

A

They contain mycolic acid and a ton of lipids.

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67
Q

These six organisms do not take Gram stain well:

Briefly think of why.

A

These Rascals May Microscopically Lack Color:
Treponema (too thin)
Rickettsia (intracellular)
Mycobacteria (high lipid content, need carbolfuschin)
Mycoplasma (no cell wall)
Legionella (mostly intracellular)
Chlamydia (intracellular)

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68
Q

How do you visualize Chlamydia?

A

Giemsa stain

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69
Q

When would you use the Ziehl-Neelsen carbol fuschin stain (2)?

A

For acid-fast organisms (2):
Mycobacteria
Nocardia

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70
Q

Six organisms you would stain with Giemsa:

A 
Certain Bugs Really TRY His Patience
Chlamydia
Borrelia
Rickettsiae
Trypanosomes
Histoplasma
Plasmodium
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71
Q

Four cases in which you would use silver stain:

A

Fungi
Legionella
Pneumocystis
H. pylori

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72
Q

What does PAS stain for?

A

Glycogen

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73
Q

Stain you would use to diagnose Whipple’s disease:

A

PAS

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74
Q

Stain you would use to diagnose Cryptococcus:

A

India ink

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75
Q

Stain you would use to diagnose Nocardia:

A

Carbol fuschin (Ziehl-Neelsen)

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76
Q

Stain you would use to diagnose Borrelia:

A

Giemsa

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77
Q

Stain you would use to diagnose Legionella:

A

Silver

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78
Q

Stain you would use to diagnose Histoplasma:

A

Giemsa

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79
Q

Stain you would use to diagnose Pneumocystis:

A

Silver

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80
Q

Stain you would use to diagnose Chlamydia:

A

Giemsa

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81
Q

Gram (+) organisms stain ____.

Gram (-) organisms stain ____.

A

Blue

Pink

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82
Q

These four organisms are obligate aerobes:

A 
Nagging Pests Must Breathe:
Nocardia
Pseudomonas AERuginosa (think aerate)
Mycobacterium tuberculosis
Bacillus
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83
Q

Obligate aerobe seen in burn wounds, causes pneumonia in patients with CF:

A

Pseudomonas aeruginosa

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84
Q

These three bugs are obligate anaerobes:

Why?

A 
Can't Breathe Air:
Clostridium
Bacteroides
Actinomycetes
They do not have catalase or SOD, cannot deal with oxygen.
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85
Q

Treatment for infection with obligate anaerobes:

A

Metronidazole

Clindamycin

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86
Q

This class of antibiotics requires oxygen to enter a cell:

A

AminOglycosides

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87
Q

These two bugs are obligate intracellular creatures, they cannot make ATP:

A

Rickettsiae

Chlamydia

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88
Q

These bugs are facultative intracellular pests (7):

A 
Some Nasty Bugs May Live FacultativeLY:
Salmonella
Neisseria
Brucella
Mycobacterium
Listeria
Francisella
Legionella
Yersinia pestis
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89
Q

These bacteria are encapsulated (8):

A 
Even Some Pretty Nasty Killers Have Shiny Bodies:
E. coli
Strep pneumo
Pseudomonas
Neisseria
Klebsiella
H. influ
Salmonella typhi
gB Strep
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90
Q

Asplenics are at risk for infection with these bacteria (8):

A 
Even Some Pretty Nasty Killers Have Shiny Bodies:
E. coli
Strep pneumo
Pseudomonas
Neisseria
Klebsiella
H. influenzae
Salmonella typhi
group B Strep
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91
Q

These organisms make catalase (7):

A 
You need PLACESS for CATs.
Pseudomonas
Listeria
Aspergillus
Candida
E. coli
S. aureus
Serratia
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92
Q

Organisms you may be susceptible to infection with if you have NADPH oxidase deficiency:

A 
These organisms readily break down the limited amount of H2O2 people with this def. have.  They are:
PLACESS for CATs:
Pseudomonas
Listeria
Aspergillus
Candida
E. coli
Serratia
Staph. aureus
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93
Q

Yellow-pigmented colonies (2):

A

Staph aureus

Actinomyces israelii

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94
Q

Blue-green pigmented organism:

A

Pseudomonas aeruginosa

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95
Q

Red-pigmented organism:

A

Serratia marcescens

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96
Q

These organisms are urease-positive (8):

A 
CHuck norris hates PUNKSS:
Cryptococcus
H. pylori
Proteus
Ureaplasma
Nocardia
Klebsiella
S. epidermidis
S. saprophyticus
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97
Q

What is the function of bacterial protein A?

Which organism makes this?

A

This binds Fc of Ig and prevents host immune cells from phagocytosing the bacterium. S. aureus makes this.

98
Q

Which bugs make IgA protease?

A

These are all respiratory pathogens:
S. pneumo
H. iB
Neisseria

99
Q

What is M protein, and which bacteria make this?

A

M protein inhibits phagocytosis:
Don’t Munch me, I will give you GAS:
Group A Strep

100
Q

Where is the genetic material coding for exotoxin production located?
For endotoxin?

A

Exotoxin DNA is stored in plasmids or bacteriophages.

Endotoxin DNA resides in the bacterial chromosome.

101
Q

Where is endotoxin found?

A

On Gram (-)s, their outer membrane.

102
Q

Which kind of toxin is destroyed quickly by heat?

Which is more stable to high temps?

A

Exotoxin is easily destroyed by heat.

Endotoxin you can cook.

103
Q

Six main toxins made by Staph aureus, two words about what they do:

A
  1. a-toxin -> hemolysis
  2. b-toxin -> sphingomyelinase
  3. leukocidin
  4. enterotoxins (A-E) -> food poisoning
  5. TSST-1 -> toxic shock syndrome
  6. Exfoliative / epidermolytic toxin -> scalded skin
104
Q

Three main toxins made by Strep pyogenes, two words about what they do:

A
  1. Streptolysin O (O2 Labile) &
  2. Streptolysin S (O2 Stable) -> hemolysis
  3. Erythrogenic pyrogenic toxins -> rash / fever, cause scarlet fever
105
Q

These two toxins inhibit EF-2:

Which bacteria make them?

A 
Diphtheria toxin
Exotoxin A (made by Pseudomonas)
106
Q

These two toxins remove a residue from our rRNA coding for our 60S ribosomal subunit:
Which bacteria make them?

A 
Shiga toxin (made by Shigella)
Shiga-like toxin (made by enterohemorrhagic E. coli)
107
Q

This toxin mediates hemolytic uremic syndrome:

What was the triad again?

A

Shiga or shiga-like toxin

  1. Anemia
  2. Thrombocytopenia
  3. Acute renal failure
108
Q

T/F: Enterohemorrhagic E. coli invades host cells:

A

F. Shigella does this, but E. coli does not.

109
Q

This organism produces a toxin that behaves like cholera toxin. What is it, and how does the toxin work?

A

Enterotoxigenic E. coli makes a heat labile toxin, increases cAMP and Cl- secretion into the gut.
(The heat stable toxin increases cGMP and decreases NaCl resorption.)

110
Q

A strain of E. coli makes a toxin that remains when the bacterium is heated and killed. What does this toxin do?
Another organism makes a similar toxin, which one?

A

This is heat stable toxin
Increases cGMP, slows NaCl and thus water resorption in the gut -> watery diarrhea
Yersinia enterocolitica does something similar

111
Q

Four toxins that act to increase cAMP. Which organisms make them, what is their effect?

A

cGMP increase with:
E. coli heat-labile toxin, watery diarrhea
Cholera toxin, rice-water stools
(Both of these are high Cl- secretion mechs)
Bacillus anthracis makes edema factor
Pertussis toxin disables Gi, effect is impaired phagocytosis

112
Q

Two toxins that cleave SNARE proteins:

What type of paralysis results from each?

A 
Tetanospasmin (prevents inhibitory neurotransmitter release -> spastic paralysis)
Botulinum toxin (prevents ACh release -> flaccid paralysis)
113
Q

Mechanism of action of pertussis toxin:

A

Breaks Gi

Increases cAMP

114
Q

Mechanism of action of alpha toxin made by Clostridium:

A

Phospholipase, breaks down tissues and cell membranes, causes necrosis

115
Q

This Strep. pyogenes toxin degrades cell membranes:

A

Streptolysin O
This is the toxin that LYSES cell membranes
This is also the SO of ASO, eg Ab titers for RF

116
Q

These two superantigens cause shock:

Which organism makes them?

A 
TSST-1 (made by Staph aureus)
Exotoxin A (made by Strep. pyogenes)
117
Q

S. pneumo, H. influenzae, and Neisseria are able to undergo transformation. What does this mean?

A

Can take up naked DNA from their environment.

118
Q

How is plasmid DNA transferred from bacterium to bacterium?

A

During conjugation, F+ x F- meet

119
Q

What is a Hfr cell? What kind of genetic material is transferred when Hfr x F- during conjugation?

A

Hfr = an F+ plasmid (plasmid with the pilus instructions) incorporated into chromosomal DNA.
Conjugation -> transfer of plasmid and chromosomal information that just happened to be near the plasmid insertion point.

120
Q

What is transduction?

A

Infection with a bacteriophage, can go two ways.

  1. Phage carries some bacterial DNA with it when it lyses (vanilla)
  2. Phage inserts itself into bacterial DNA, when it lyses it carries flanking genes with it.
121
Q

These five toxins are carried by lysogenic phages:

A 
ABCDE:
ShigA-like toxin
Botulinum toxin
Cholera toxin
Diphtheria toxin
Erythrogenic toxin (Strep pyo.)
122
Q

Gram (+) cocci in clusters:

Gram (+) cocci in chains:

A

Staph

Strep

123
Q

5 Gram (+) rods:

A 
Clostridium
Corynebacterium
Listeria
Bacillus
Mycobacteria
124
Q 
Two Gram (+) branching filaments:
Which is an aerobe?
A

Actinomyces
Nocardia
Nocardia is the aerobe

125
Q

What is alpha hemolysis?

Which Strep. sp are a-hemolytic?

A

Partial hemolysis = a-hemolysis
Strep pneumo
Viridans strep

126
Q

What is beta hemolysis?

Which Strep. sp are b-hemolytic?

A 
b-hemolysis = complete hemolysis
Strep pyogenes (= GAS)
Strep agalactiae (= GBS)
127
Q

What is the difference in antibiotic sensitivity between group A and B Strep?

A 
GAS = pyogenes = bacitracin-sensitive
GBS = agalactiae = bacitracin-resistant
128
Q

What is gamma hemolysis?

Which Strep. sp are g-hemolytic?

A

g-hemolysis = no hemolysis at all
Enterococci
Non-enterococci (Strep. bovis)

129
Q

How do you tell between Strep pneumoniae and viridans group strep?

A
  1. S. pneumo has a capsule, Quellung will be (+). It is Optochin sensitive.
  2. Viridans strep. have no capsule (Quellung negative) and are Optochin resistant. Remember the viridans Strep. are mouth bacteria, they are OFF the CHIN resistant.
130
Q

Which bacteria are beta-hemolytic, how will you tell them apart (4)?

A 
Staph aureua (coag and cat +)
Strep pyogenes (GAS) (cat neg, optochin sensitive)
Strep agalactiae (GBS) (cat neg, optochin resistant)
Listeria monocytogenes (tumbling motility)
131
Q

Mechanism by which MRSA are b-lactamase resistant:

A

Altered PCN binding proteins.

132
Q

This Staph. sp is known for infecting prosthetic devices and IV catheters:

A

Staph. epidermidis

133
Q

Most common cause of meningitis:

A

Strep pneumoniae

134
Q

Gram (+) diplococcus associated with sepsis in sickle cell anemia:

A

Strep pneumoniae

135
Q

This normal member of our oral flora causes dental caries:

A

Strep. mutans

136
Q

Which of the a-hemolytic Strep. groups is optochin-sensitive?
Which is optochin-resistant?

A

Strep. pneumoniae = optochin sensitive

Strep. viridans = optochin resistant

137
Q

These three organisms make an IgA protease:

A

HiB
Neisseria meningitidis
S. pneumoniae

138
Q

Cause of rheumatic fever:

A

Strep pyogenes (GAS)

139
Q

Jones criteria:

A

Joints

s chorea

140
Q

Which Strep pyogenes infection is most likely to precede glomerulonephritis?

A

Impetigo > pharyngitis.

141
Q

Three organisms particularly deadly to babies:

A

GBS
E. coli
Listeria

142
Q

Which is the more burly organism: Enterococcus or non-enterococcus group D?

A

Enterococci. You can grow them in bile AND salt.

143
Q

This b-hemolytic Strep. is bacitracin-resistant as a rule:

A

Strep agalactiae (GBS) is bacitracin-resistant.

144
Q

This titer detects recent infection with S. pyogenes:

145
Q

Strep. sp associated with colon cancer:

A

Streptococcus bovis

146
Q

Mechanism of action of diphtheria toxin:

A

EF-2 inhibitor

just like Pseudomonas

147
Q

Gram (+) club-shaped rods with metachormatic red-blue granules:

A

Corynebacterium diphtheriae

148
Q

Black colonies on cystine-tellurite agar:

A

Corynebacterium diphtheriae

149
Q

Treatment for diphtheria:

A

Penicillin or erythromycin.
May want to give diphtheria antitoxin.
Vaccinate (again) too.

150
Q

Spore-forming bacteria:

A 
Bacillus anthracis
Bacillus cereus
Clostridium botulinum
Clostridium perfringens
Clostridium tetani
Coxiella burnetii (rickettsial, causes Q-fever)
151
Q

The two toxins produced by Clostridium dificile and their MOA:

A
  1. Toxin A = enterotoxin, binds to enterocytes

2. Toxin B = cytotoxin, destroys cytoskeleton of enterocytes

152
Q

This bacterium has a polypeptide capsule containing D-glutamate:

A

Bacillus anthracis

Remember, it has a weird ENVELOPE. You would not want it at the post office.

153
Q

Some nice wool-comber develops pulmonary anthrax. What do you expect will happen to them?

A

Look like they have the flu.
Suddenly they have a fever, shock.
Pulmonary hemorrhage and mediastinitis.

154
Q

Nausea and vomiting in 1-5 hours after eating reheated rice:

What is the toxin responsible?

A

Bacillus cereus

Cereulide

155
Q

Unpasteurized milk / dairy / vaginal transmission of an organism with tumbling motility:
What does this little guy look like on Gram stain?

A

Listeria

Gram (+) rod

156
Q

Treatment for Listeria:

A

Ampicillin

157
Q

Oral / facial abscess, yellow sulfur-granule appearance. How do you treat it?

A

This is Actinomyces.

Tx is penicillin.

158
Q

Gram (+) filamentous branching aerobe. Treatment?

A

Nocardia, treatment is sulfonamides.

159
Q

Why might someone be PPD (-) (3 reasons)?

A

No infection
Anergy (steroids, malnutrition, immunocompromised)
Sarcoidosis

160
Q

What is a Ghon complex?

A

A Ghon focus + hilar LAD, seen in primary TB.

161
Q

What is the recommended prophylactic treatment for MAC?

A

Azithromycin

162
Q

Treatment for leprosy:

A

Dapsone
Clofazimine
Rifampin

163
Q

This form of leprosy is communicable. What T cell response will you characteristically see?

A

Lepromatous, TH2 dominant response. Diffuse presentation over the skin.

164
Q

Second most common cause of Gram (-) sepsis:

A

Klebsiella

165
Q

Mesenteric adenitis that might look a lot like Chron’s:

A

Yersinia enterocolitica

166
Q

Three symptoms of leptospirosis:

Who gets this disease and from where?

A

Jaundice
Photophobia
Conjunctivitis
Surfers in the tropics, it’s found in water contaminated with animal urine.

167
Q

What is Weil’s disease?

A

Severe leptospirosis:
Jaundice
Liver / kidney dysfx, azotemia
Hemorrhage / anemia

168
Q

Question mark shaped organism, flu-like symptoms:

A

Leptospira interrogans

169
Q

Treatment for Lyme disease:

A

Doxycycline

Ceftriaxone

170
Q

Natural reservoir for Borrelia burgdorferi:

Vector:

A

Mouse

Carried by Ixodes tick

171
Q

Characterizes primary syphilis:

A

Single painless chancre

172
Q

Rash on palms and soles, 3 possibilities:

A

Syphilis (secondary)
RMSF
Coxsackie A virus

173
Q

Alopecia areata, rash on palms and soles:

A

Secondary syphilis

174
Q

What is a Charcot joint?

A

Damage done to joints because they are insensate. Usually in DM, can be seen in tertiary syphilis.

175
Q

This is an early sign of congenital syphilis:

A

The snuffles.
(Cute. Or not.)
Blood-tinged nasal secretions.

176
Q

Tertiary syphilis can do this to an aorta:

A

Destruction of the vaso vasorum that feed the aorta itself, causes “tree-barking”

177
Q

What is an Argyll-Robertson pupil?

A

A pupil that constricts with accomodation but fails to react to light. AKA the prostitute’s pupil. Seen in tertiary syphilis.

178
Q

What are some common scenarios where you might see false positives with VDRL testing?

A 
VDRL!
Viruses (mono and hepatitis)
Drugs
Rheumatic fever
Lupus / Leprosy
179
Q

This organism causes the yaws:

Think of a couple features of the yaws.

A

Treponema pertenue

Disease of skin / joints, healing with keloids, disfigurement, face commonly involved.

180
Q

What happens to immunocompromised people who get cat scratch disease?

A

May develop angiomatosis that looks like Kaposi’s sarcoma.

181
Q

Appearance of Gardnerella vaginalis on LM:

A

Gram-variable

Pleomorphic

182
Q

Treatment for all the Rickettsial diseases:

A

Doxycycline

183
Q

How does the rash of RMSF differ from the rash seen in typhus?

A

RMSF: Rash starts at wRists and moves in.
Typhus: Rash starts on the Trunk and moves out.

184
Q

Epidemic typhus:

A

Rickettsia prowazekii

R. typhi is the endemic form

185
Q

Morula-like cytoplasmic inclusion, tick-borne:

186
Q

What is Q fever?

A

Caused by Coxiella burnetii.
Causes interstitial pneumonia.
No rash.

187
Q

What is unusual about the cell wall of Chlamydia?

A

It has no muramuic acid

188
Q

Treatment for chlamydial infections:

A

Azithromycin, single dose

189
Q

Three most common causes of atypical pneumonia:

A

Mycoplasma
Legionella
Chlamydophila pneumoniae

190
Q

What are the three pathogenic Chlamydial sp?

A

C. trachomatis
C. pneumoniae
C. psittaci

191
Q

What is lymphogranuloma venereum?

A

Infection with Chlamydia trachomatis type L1-L3, causes inguinal lymphadenitis with a primary ulcer, may mimic UC and cause rectal disease.

192
Q

Why do we give babies azithromycin eye drops at birth?

A

Worry for congenital transmission of Chlamydia, which can cause conjunctivitis and neonatal pneumonia.

193
Q

Chalmydia trachomatis serotypes associated with blindness in Africa:

194
Q

T/F: C. trachomatis infection can cause ectopic pregnancy.

A

T. PID can make the uterus an unfriendly place, embryo might just go find another home.

195
Q

Atypical pneumonia with a high titer of cold agglutinins:

How would you treat such an infection?

A

Mycoplasma pneumoniae

Tx is with fluoroquinolone or macrolide

196
Q

This aminopenicillin is usually given orally.
This one is usually given IV.
What infections do they treat?

A 
Ampicillin is usually used IV.
AmOxicillin is better Oral.
Used to HELPSS kill enterococci:
H. influ
E. coli
Listeria
Proteus mirabilis
Salmonella
Shigella
enterococci
197
Q

Usual mechanism of resistance to ampicillin / amox:

A

b-lactamases

198
Q

What is augmentin made of:

A

Amoxicillin + clavulanic acid = augmentin

199
Q

What is unasyn composed of:

A

Ampicillin + sulbactam

Used IV

200
Q

What is zosyn made of:

A

Piperacillin + tazobactam

201
Q

The three b-lactamase inhibitors:

A

Clavulanic acid
Sulbactam
Tazobactam

202
Q

Penicillin associated with development of pseudomembranous colitis:

A

Aminopenicillins, amp and amox

203
Q

Good treatment of choice for neonatal infections with E. coli, Listeria:

A

Ampicillin

Add gentamycin just to be safe

204
Q

Treatment for uncomplicated URI with Gram (+) organisms:

A

Aminopenicillins +/- b-lactamase inhibitors

205
Q

Three anti-pseudomonal penicillins:

A

Ticarcillin
Piperacillin
Carbenicillin

206
Q

Treats pseudomonas and Gram (-) rods:

A

Ticarcillin
Piperacillin
Carbenicillin

207
Q

Organisms not covered by cephalosporins:

A 
These guys are LAME:
Listeria
Atypicals (Chlamydia, Mycoplasma)
MRSA
Enterococci
208
Q

First generation cephalosporins are used to treat these infections:

A

PEcK:
Proteus
E. coli
Klebsiella

209
Q

The two first-generation cephalosporins:

A

Cefazolin

Cephalexin

210
Q

Second-generation cephalosporins cover:

A 
HEN PeCKS:
H. influ
Enterobacter
Neisseria
Proteus
E. coli
Klebsiella
Serratia
211
Q

Drug of choice for OM due to non-typeable H. flu:

A 
Second gen. cephalosporin
Consider Cefdinir (3rd gen) if resistant.
212
Q

Four second-generation cephalosporins:

A

Cefuroxime
Cefaclor
Cefoxitin
Cefprozil

213
Q

Third-generation cephalosporins add coverage for these two main infections:

A

Gram (-)s

Meningitis, gonorrhea, pseudomonas

214
Q

Fourth-generation cephalosporin:

What is it particularly good at?

A 
Cefipime
Killing pseudomonas (and everything else)
215
Q

Cephalosporins with a disulfiram-like reaction (3):

A

Cefotetan
Cefamandole
Cefoperazone

216
Q

Mechanism of action of cephalosporins:

A

Bactericidal.

Inhibit cell wall synthesis.

217
Q

Mechanism of action of aztreonam:

A

Binds PBP3 and prevents cross-linking of peptidoglycans.

218
Q

Consider this drug for someone with a Gram (-) infection, renal insufficiency, and who is PCN-allergic:

219
Q

These drugs can increase the nephrotoxicity of aminoglycosides:

A

Cephalosporins

220
Q

These two drugs have a very broad spectrum but their use is limited to life-threatening infections of unknown origin and as last resort due to toxicity:

A

Imipenam

Meropenem

221
Q

Drug you give with imipenam:

Why?

A

Cilastatin

Inhibits renal dehydropepdisase I, which inactivates the drug.

222
Q

T/F: Meropenam will cover MRSA.

A

F. You need to give vanc for that. Typical scenario is sepsis of unknown origin, must give carbapenam + vanc to cover for MRSA.

223
Q

Mechanism of action of vancomycin:

A

Bactericidal.

Binds D-ala D-ala on cell wall of bacteria, inhibits peptidoglycan formation.

224
Q

Spectrum of coverage for vancomycin:

A

Gram (+) only.

Especially useful for MRSA, enterococci, C. diff.

225
Q

Three primary toxicities of vanc:

A

Nephrotoxic
Ototoxic
Thrombophlebitis
Also, Red Man syndrome

226
Q

Mechanism of resistance to vancomycin:

A

D-ala D-ala becomes D-ala D-lac in resistant organisms.

Remember, D-lac = vancomycin activity LACking.

227
Q

Prophylaxis for M. tb:

228
Q

Prophylaxis for MAC:

A

Azithromycin / clarithromycin

When CD4 count < 50

229
Q

Treatment for M. tb:

A 
RIPE:
Rifampin
Isoniazid
Pyrazinamide + pyridoxine (B6)
Ethambutol
The B6 prevents isoniazid toxicity
230
Q

Treatment for MAC infections:

A

Clarithromycin + ethambutol

231
Q

Treatment for M. leprae infection:

A

Dapsone
Rifampin
Clofazimine

232
Q

Mechanism of action of isoniazid:

A

Decreases mycolic acid synthesis

233
Q

Administering this vitamin can help prevent isoniazid neurotoxicity:

234
Q

Three main toxicities associated with isoniazid:

A

Neurotoxicity
Hepatotoxicity
Drug-induced lupus

235
Q

Mechanism of action of rifampin:

A

Inhibits DNA-dependent RNA-pol.

236
Q

This drug is used for prophylaxis of meningitis and HiB chemoprophylaxis:

237
Q

Drug that causes orange body fluids:

238
Q

Main pharmacokinetic consideration with rifampin:

A

Increases P-450 enzymes, speeds the metabolism of many drugs.

239
Q

Mechanism of action of pyrazinamide:

It has a really great advantage for M. tb:

A

Blocks fatty acid synthesis in mycobacteria.

It works well at acid pH, ie in lysosomes where M. tb likes to hide.

240
Q

This drug blocks arabinosyltransferase and therefor decreases carb. polymerization in Mycobacteria cell walls:

A

Ethambutol

241
Q

Main side effect of ethambutol:

A

Optic neuropathy

USMLE Step 1 (18 decks)

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