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STEP 1 Microbiology > GI/urinary- Bacteria and antibiotics > Flashcards

GI/urinary- Bacteria and antibiotics Flashcards

1
Q

Enterobacter- Transmission

A

Nosocomial; multi-drug resistance

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2
Q

Serratia- Transmission

A

Nosocomial; multi-drug resistance

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3
Q

Klebsiella- Transmission

A

Nosocomial; multi-drug resistance; commonly affect alcoholics; common in cases of aspiration

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4
Q

Enterobacter- diagnosis

A

Lactose fermenter (pink colonies on McConkey agar)

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5
Q

Serratia- diagnosis

A

(Slow) Lactose fermenter (pink colonies on McConkey agar, but may appear negative at first); produces red pigment when cultured

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6
Q

Klebsiella- diagnosis

A

Lactose fermenter (pink colonies on McConkey agar)

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7
Q

Bacteria that ferment lactose

A

1) Enterobacter
2) Klebsiella
3) Serratia
4) E. coli

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8
Q

How is lactose fermentation observed?

A

Pink colonies on McConkey agar

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9
Q

Enterobacter- morphology

A

Gram-negative rods, facultative anaerobic, motile

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10
Q

Serratia- morphology

A

Gram-negative rods, facultative anaerobic, motile

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11
Q

Klebsiella- morphology

A

Gram-negative rods, oxidase-negative, urease-positive, prominent polysaccharide capsule (mucoid colonies), nonmotile

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12
Q

Klebsiella- presentation

A
  • Pneumonia with currant jelly sputum and abscesses (may mimic TB)
  • UTIs, struvite stones
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13
Q

Salmonella typhi- morphology

A

Gram-negative rods; facultative intracellular (within macrophages), motile

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14
Q

Salmonella enteritidis- morphology

A

Gram-negative rods; facultative intracellular (within macrophages), motile

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15
Q

Salmonella typhi- presentation

A
  • Typhoid fever
  • Rose-colored macules on abdomen (25%); osteomyelitis in sickle cell disease (#1 cause)
  • Constipation or “pea soup” diarrhea, GI ulceration/hemorrhage
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16
Q

Salmonella enteritidis- presentation

A

Inflammatory diarrhea

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17
Q

Salmonella typhi- diagnosis

A

H2S positive (black colonies on Hektoen agar), encapsulated, acid-labile (degraded in stomach)

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18
Q

Salmonella enteritidis- diagnosis

A

H2S positive (black colonies on Hektoen agar), encapsulated, acid-labile (degraded in stomach)

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19
Q

Salmonella typhi- treatment

A

Fluoroquinolone (i.e. cipro) or ceftriaxone

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20
Q

Salmonella enteritidis- treatment

A

None (antibiotics not indicated)

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21
Q

Salmonella enteritidis- transmission

A

Undercooked chicken (reservoir)

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22
Q

Which salmonella type has a vaccine? What type?

A

Salmonella typhi; live-attenuated

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23
Q

Salmonella- virulence

A

Type III secretion system detects eukaryotic cells (injectisome)

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24
Q

E. coli- morphology

A

Gram-negative rods; facultative anaerobic, encapsulated, catalase-positive

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25
E. coli- diagnosis
- Lactose fermenter (pink on McConkey agar) - Green on EMB agar - May have K antigen on capsule (serotyping)
26
E. coli- virulence (general)
- Fimbriae (#1 cause of UTIs) | - LPS (#1 cause of gram-negative sepsis)
27
When can E. coli cause neonatal meningitis?
When it has the K antigen
28
EHEC- presentation
"Enterohemorrhagic," bloody diarrhea; HUS (usually children under 10)
29
EHEC- transmission
Undercooked meat
30
How can EHEC be distinguished from other E. coli strains in a lab?
EHEC is the only one that does not ferment sorbitol
31
EHEC virulence
Shiga-like toxin inhibits ribosomes at 60S subunit
32
Hemolytic uremic syndrome pathogenesis in E. coli
Shiga-like toxin damages endothelial cells in capillaries of the glomerulus. Damaged lining becomes thrombogenic, causing platelets to adhere. Platelets lyse RBCs as they pass through the capillaries.
33
Serotype of EHEC that causes massive outbreaks
0157:H7 antigen
34
ETEC- presentation
Traveler's diarrhea (watery)
35
ETEC- virulence
- Heat labile toxin increases cAMP | - Heat stable toxin increases cGMP
36
Yersinia enterocolitica- morphology
Gram-negative rods; encapsulated
37
Yersinia enterocolitica- transmission
- Dog feces (commonly affects toddlers) - Contaminated milk products (resistant to cold) - Chitterlings
38
Yersinia enterocolitica- diagnosis
Bipolar staining ("safety pin")
39
Yersinia enterocolitica- presentation
Bloody diarrhea, fever, leukocytosis, abscesses, intestinal perforation; mimics appendicitis (RLQ pain)
40
Campylobacter jejuni- morphology
Curved Gram-negative rods; motile, oxidase-positive
41
Campylobacter jejuni- presentation
Bloody diarrhea, bacteremia (invasive), Reiter syndrome, Guillain- Barre (ascending paralysis)
42
Campylobacter jejuni- transmission
Thermophilic (42 degrees C); main reservoir is intestinal tract of animals (ie poultry); technically, fecal-oral route
43
Vibrio cholerae- morphology
Curved Gram-negative rod (comma-shaped), oxidase-positive, acid-labile
44
Vibrio cholerae- transmission
Endemic to developing countries; fecal-oral spread by water contamination
45
Vibrio cholerae- presentation
Profuse, "rice-water" diarrhea
46
Vibrio cholerae- virulence
Uses fimbriae to attach to ganglioside receptors in the intestinal wall; secretes cholera toxin Increases cAMP by constitutively activating adenylate cyclase (Gs pathway);
47
How does cholera toxin work?
Increases cAMP by constitutively activating adenylate cyclase (Gs pathway). cAMP stimulates Cl- secretion by CFTR. Sodium and water follow.
48
Vibrio cholerae- treatment
Oral rehydration therapy
49
Vibrio cholerae
Grows on alkaline media
50
Where are Vibrio vulnificus and Vibro parahemolyticus found?
Seafood contamination (especially oysters)
51
Helicobacter pylori- morphology
Curved Gram-negative rod; urease-positive, oxidase positive
52
Helicobacter pylori- transmission
Duodenal ulcers, gastric adenocarcinoma, MALT lymphoma (usually goes away by treating H. pylori)
53
Helicobacter pylori- treatment
Triple therapy: 1) PPi 2) Amoxycillin 3) Macrolide (Clarithromycin)
54
Helicobacter pylori- treatment
Triple therapy: 1) PPi 2) Amoxycillin 3) Macrolide (Clarithromycin)
55
Helicobacter pylori- virulence
Urease reduces acidity of environment for invasion of stomach
56
How does urease work?
Splits urea into ammonium and CO2
57
How does urease work?
Splits urea into ammonium and CO2
58
Pseudomonas- morphology
Gram-negative rods; encapsulated, obligate aerobe, oxidase-positive, catalase-positive
59
Pseudomonas- presentation
- Hot tub folliculitis (pruritic, papular, pustular) - Nosocomial pneumonia - Respiratory failure in cystic fibrosis - Osteomyelitis in IV drug users and diabetics (due to neuropathy) - Infection in burn patients (often lethal) - Indwelling catheter infections/UTIs - Ecthyma gangrenosum (black, necrotic lesions on skin in sepsis) - Otitis externa
60
Pseudomonas- diagnosis
- Blue-green pigment on plate, due to pyocyanin and pyoverdin (may even turn wounds blue) - Fruity, grape-like odor
61
Pseudomonas- virulence
Exotoxin A (similar to diphtheria toxin; inactivates EF-2 by ribosylation)
62
Pseudomonas- treatment
- Piperacillin + Tazobactam - Aminoglycosides - Fluoroquinolones (especially UTIs)
63
Pseudomonas- transmission
Thrives in aquatic environments
64
Proteus mirabilis- morphology
Gram-negative; urease-positive
65
Proteus- presentation
- Struvite stones | - UTIs
66
Proteus mirabilis- diagnosis
- Swarming motility when plated | - Fishy odor
67
Proteus mirabilis- virulence
Urease needed to form staghorn calculi (alkaline environment from ammonia and CO2)
68
What are struvite stones composed of?
Ammonia, magnesium, phosphate
69
Proteus mirabilis- treatment
Sulfonamides
70
Bacillus anthracis- morphology
Large Gram-positive rods in chains; obligate aerobe, encapsulated (made of poly-D glutamate, rather than polysaccharide), spore-forming
71
Bacillus cereus- morphology
Gram-positive rods in chains; facultative anaerobic, motile, beta-hemolytic, spore-forming
72
Bacillus anthracis- presentation
- Black eschar - Pulmonary anthraw (Woolsorter's disease), which starts as a dry cough but can migrate to mediastinal lymph nodes and cause hemorrhagic mediastinitis (widened mediastinum on X-ray)
73
Bacillus cereus- presentation
Fried rice syndrome (vomiting)
74
Bacillus cereus- transmission
Eating reheated fried rice
75
Is Bacillus anthracis beta-hemolytic?
No
76
Is Bacillus cereus beta-hemolytic?
Yes
77
Clostridium difficile- morphology
Gram-positive rods in pairs/short chains; anaerobic, motile, spore-forming
78
Clostridium difficile- presentation
Nosocomial diarrhea
79
Clostridium difficile- virulence
- Exotoxin A ("apple"), which binds to brush border, causing inflammation, cell death, and watery diarrhea - Exotoxin B ("black licorice"), which disrupts the cytoskeleton by depolymerizing actin, causing enterocyte death and necrosis; forms pseudomembrane (yellow-gray) that covers colonic mucosa
80
Clostridium difficile- treatment
- ORAL vancomycin - Fidaxomicin - Metronidazole
81
Antibiotic classically associated with C. diff
Clindamycin
82
Clostridium difficile- diagnosis
- PCR/assay for toxin - Direct visualization of the pseudomembrane - Characteristic odor
83
What type of infection is classically observed in patients with colonic carcinoma?
Streptococcus bovis
84
Streptococcus bovis- morphology
Gram-positive cocci in chains; group D strep, oxidase-negative, catalase-negative

STEP 1 Microbiology (22 decks)

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