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USMLE Step 1-2015 > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Bugs that do not gram stain well

A

“These microbes may lack real color”

Treponema, Mycobacteria, Mycoplasma, Legionella, Rickettsia, Chlamydia

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2
Q

Giemsa stain

A

“Certain Bugs Really Try my Patience”

Chlamydia, Borrelia, Rickettsia, Trypanosomes, Plasmodium

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3
Q

PAS

A

Stains glycogen (used to diagnose whipple disease (T. Whippeli))

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4
Q

Ziehl-Neelsen (carbol fuchsin)

A

nocardia, mycobacteria (acid fast bacteria), cryptosporidium oocysts (protozoa)

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5
Q

India ink

A

Crytococus neoformans

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6
Q

Sliver stain

A

Fungi (e.g. pneumocystis), Legionella, H. pylori

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7
Q

Alternative to ziehl-neelsen for screening (more sensitive but less specific)

A

Auramine-Rhodamine stain

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8
Q

H influenzae media used for isolation?

Important media contents?

A

Chocolate agar, Factors V (NAD+) and X (hematin)

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9
Q

N gonorrhoeae, N meningitidis media used for isolation?Important media contents?

A

Thayer-Martin, Vancomycin (inhibits gram-positive organisms), Trimethoprim, Colistin (inhibits gram-negative organisms except neisseria), and Nystatin (inhibits fungi)
“Very Typically Cultures Neisseria”

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10
Q

B. pertussis media used for isolation? media contents?

A

1) Bordet-gengou agar (Bordet for bordetella)–>Potato

2) Regan-lowe medium (charcoal, blood, and antibiotic)

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11
Q

C diphtheria media used for isolation?

A

Tellurite agar, Loffler medium

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12
Q

M tuberculosis media used for isolation?

A

Lowenstein-Jensen agar

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13
Q

M. pneumoniae media used for isolation? important media contents?

A

Eaton agar, requires cholesterol

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14
Q

Lactose fermenting enterics media used for isolation? Important media contents/other?

A

MacConkey agar. Fermentation produces acid, causing colonies to turn pink

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15
Q

E. coli media used for isolation? Important media contents/other?

A

Eosin-methylene blue (EMB) agar. Colonies with green metallic sheen

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16
Q

Legionella media used for isolation?

A

Charcoal yeast extract agar buffered with cystein and iron

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17
Q

Fungi media used for isolation?

A

Sabourraud agar “sab’s a fun guy”

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18
Q

Aerobes

A

Nocardia, Pseudomonas, MycoBacterium tuberculosis (Naggigng Pests Must Breathe)

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19
Q

Anaerobes

A

Fusobacterium, Clostridium, Bacteioides, and Actinomyces (Frankly Can’t Breath Air)

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20
Q

What type of drug is ineffective against anaerobes?

A

Aminoglycosides b/c require O2 to enter into bacterial cell

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21
Q

4 key characteristics of anaerobes.

A

1) Suceptible to oxidative damage with no catalase/superoxide dismutase
2) Foul smelling (Short-chain fatty acids)
3) Difficult to culture
4) Produce gas in tissues (CO2 and H2)

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22
Q

Obligate intracellular

A

Rickettsia, CHlamydia, COxiella. Rely on host ATP “Stay inside (cells) when it is Really CHilly and COld”

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23
Q

Facultative intracellular

A

Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, Yersinia pestis (Some Nasty Bugs May Live FacultativeLY)

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24
Q

Encapsulated bacteria

A

SHiNE SKiS
Strep pneumoniae, H. influenzae type B, Neisseria Meningitidis, E. Coli, Salmonella, Kelbseilla pneumoniae, group B Strep

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25
Urease positive organisms
Cryptococcus, H pylori, proteus, Ureaplasma, Nocardia, Kebsiella, S epidermidis, S saprophyticus (CHuck Norris hates PUNKSS)
26
Catalase positive organisms
Nocardia, Pseudomonas, Listeria, Aspergillus, Candida, E. coli, Staphylococci, Serratia (Cats Need PLACESS to hide)
27
Pigment producing bacteria: | Actinomyces israelii-->
Yellow "sulfur" granules
28
Pigment producing bacteria: | S. Auereus-->
Yellow pigment
29
Pigment producing bacteria: | Pseudomonase aeuroginosa-->
Blue-green pigment
30
Pigment producing bacteria: | Serratia marcescens-->
Red pigment
31
IgA protease expressed by?
SHiN (includes gonorrhoae and meningitidis here) organisms (IgA protease-enzyme the cleaves IgA)
32
Protein A expressed by?
S. auereus (Protein A-Binds to Fc Region of IgG preventing phagocytosis and opsonization)
33
M protein expressed by?
group A streptococci. M protein helps prevent phagocytosis and share similar epitopes to human cellular proteins (molecular mimicry)
34
Injectisome
Certain gram negative bacteria (eg pseudomonas, salmonella, shigella, e. coli)
35
Exotoxin vs Endotoxin species of bacteria it can come from
Exotoxin-certain gram + and gram - | Endotoxin-outer cell membrane of most gram -
36
Exotoxin vs Endotoxin. Secreted from cell?
Exotoxin-Yes | Endotoxin-No
37
Exotoxin vs Endotoxin. Structure?
Exotoxin-Polypeptide | Endotoxin-LPS
38
Exotoxin vs Endotoxin. Location of genes?
Exotoxin-Plasmid or bacteriophage | Endotoxin-Bacterial chromosome
39
Exotoxin vs. Endotoxin. Antigenicity?
Exotoxin-Induces high-titer antibodies called antitoxins | Endotoxin-poorly antigenic
40
Exotoxin vs. Endotoxin. Vaccines?
Exotoxin-Toxoid as vaccine | Endotoxin-No vaccine
41
Exotoxin vs Endotoxin. Heat stability?
Exotoxin-destroyed rapidly at 60 degree celsius (ecept staphylococcal enterotoxin and ETEC heat stable toxin) Endotoxin-Stable at 100 degree celsius for 1 hr
42
``` Corynebacterium diphtheria Toxin? Mechanism? Function? Manifestation? ```
Toxin-Diphtheria toxin Mechanism-Inhibition of EF-2 (through ribosolation) Function-Inhibit protein synthesis Manifestation-pharyngitis with gray pseudomembranes in throat and severe lymphadenopathy (bull neck)
43
``` Pseudomonas aeruginosa Toxin? Mechanism? Function? Manifestation? ```
Toxin-Exotoxin A Mechanism-Inhibition of EF-2 (through ribosolation) Function-Inhibit protein synthesis Manifestation-Host cell death
44
``` Shigella spp Toxin? Mechanism? Function? Manifestation? ```
Toxin-Shiga toxin Mechanism-Inactivate 60 S ribosome by removing adenine from rRNA (inhibiting protein synthesis and eventual cell death) Function-Inhibit protein synthesis Manifestation-GI mucosal damage--> dysentery; Shiga toxin also enchances cytokine release, causing hemolytic uremic syndrome.
45
``` Enterohemorrhagic E. coli (EHEC) Toxin? Mechanism? Function? Manifestation? ```
Toxin-Shiga-like toxin Mechanism-Inactivate 60 S ribosome by removing adenine from rRNA (inhibiting protein synthesis and eventual cell death) Function-Inhibit protein synthesis Manifestation-Cytokine release, causing HUS (prototypically in EHEC serotype 0157: H7). Unlike shigella, EHEC does not invade host cells
46
``` Enterotoxigenic E. Coli (ETEC) Toxin? Mechanism? Function? Manifestation? ```
Toxin-Heat labile toxin Mechanism- Overactivates adenylate cyclase (increase cAMP)-->increase Cl- secretion in gut and H2O efflux Function-increase fluid secretion Manifstation-Watery diarrhea (leading cause of travelers diarrhea) Toxin-Heat stable toxin Mechanism-Overactivates guanylate cyclase (increase cGMP)--> decrease resorption of NaCl and H20 in gut Function-increase fluid secretion Manifestation-Watery diarrhea( leading cause of travelers diarrhea)
47
``` Bacillus anthracis Toxin? Mechanism? Function? Manifestation? ```
Toxin-Edema toxin (one of 3 components in anthrax toxin) Mechanism-mimics the adenylate cyclase enzyme (increase cAMP) Function-increase fluid secretion Manifestation-responsible for characteristic edematous borders of black eschar in cutaneous anthrax
48
``` Vibrio Cholerae Toxin? Mechanism? Function? Manifestation? ```
Toxin-cholera toxin Mechanism-overactivates adenylate cyclase (increase cAMP) by permanently activating Gs--> increase chloride secretion in gut and H20 efflux Function-increase fluid secretion Manifestation-voluminous "rice water" diarrhea
49
``` Bordetella pertussis Toxin? Mechanism? Function? Manifestation? ```
Toxin-pertussis toxin Mechanism-overactivates adenylate cyclase (increase cAMP) by disabling Gi, impairing phagocytosis to permit survival of microbe Function-inhibit phagocytic ability Manifestation-Whooping cough (child coughs on expiration and "whoops" on inspiration (toxin may not acutally be a cause of caugh; can cause 100-day cough in adults)
50
``` Clostridium tetani Toxin? Mechanism? Function? Manifestation? ```
Toxin-tetanospasmin Mechanism-Cleave SNARE (Soluble NSF attachement protein receptor), a set of proteins required for NT release via vesicular fusion Function-inhibit NT release Manifestation-Spasticity, risus sardonicus, and "lockjaw"; toxin prevents release of inhibitory (GABA and glycine) NT from renshaw cells in spinal cord
51
``` Clostridium botulinum Toxin? Mechanism? Function? Manifestation? ```
Toxin-boutlinum Mechanism-Cleave SNARE (Soluble NSF attachement protein receptor), a set of proteins required for NT release via vesicular fusion Function-inhibit NT release Manifestation-flaccid paralysis, floppy baby; toxin prevents release of stimulatory (Ach) signals at NMJ-->flaccid paralysis
52
``` Clostridium perfringens Toxin? Mechanism? Function? Manifestation? ```
Toxin-Alpha toxin Mechanism-Phospholipase (lecithinase) that degrades tissue and cell membranes Function-lyse cell membranes Manifestation-Phospholipid degradation-->myonecrosis ("gas gangrene") and hemolysis ("double zone") of hemolysis on blood agar)
53
``` S. pyogenes Toxin? Mechanism? Function? Manifestation? ```
Toxin-Streptolysin O Mechanism-Protein that degrades cell membrane Function-lyse cell membrane Manifestation-lyses RBCs; contributes to B hemolysis; host antibodies against toxin (ASO) used to diagnose rheumatic fever (do not confuse with immune complexes of poststreptococcal glomerulonephritis)
54
``` S. aureus Toxin? Mechanism? Function? Manifestation? ```
Toxin-TSST-1 Mechanism-Binds simultaneously to MHC II and TCR outside of antigen binding site to cause overwhelming release of IL-1, IL-2, IFN-gamma and TNF-alpha-->shock Function-superantigens causing shock Manifestation-toxic shock syndrome: fever, rash shock; other toxins cause scalded skin syndrome (exfoliative toxin) and food poisoning (enterotoxin)
55
``` S. pyogenes Toxin? Mechanism? Function? Manifestation? ```
Toxin-Exotoxin A Mechanism-Binds simultaneously to MHC II and TCR outside of antigen binding site to cause overwhelming release of IL-1, IL-2, IFN-gamma and TNF-alpha-->shock Function-superantigens causing shock Manifestation: Toxic shock syndrome: fever, rash, shock
56
What does toxin is an ADP ribosylating AB toxin mean?
Toxin has two components. A and B. The B (binding) component binds the host cell surface receptor allowing for endocytosis and A (active) component attaches to ADP-ribosyl to disrupt host cell proteins.
57
Addition of what will degrade naked DNA in medium preventing transformation from being seen?
Deoxyribonuclease
58
Genes for which 5 bacterial toxins are encoded in a lysogenic phage?
(ABCDE) 1) shigA like toxin 2) Botulinum toxin 3) Cholera toxin 4) Diphtheria toxin 5) Erythrogenic toxin of S. pyogenes
59
Some bacteria can form spores at the end of what phase of the bacteria life cycle?
Stationary phase when nutrients are limited
60
Spore forming organisms? "BC SPOREadically works in pregnancy?
The organisms starting with B or C make spores | Bacillus anthracis, Bacillus cereus, Clostridium botulinum, dificile, perfringens, tetani, Coxiella burnetti
61
Lactose fermenting enteric bacteria that cause pink colonies on MaConkey agar
Citrobacter, Kelbsiella, E. coli, Enterobacter, and Serratia (weak fermenter) "macConKEES"
62
EMB agar has lactose fermenters grow as what and what is the unique exception?
Lactose fermenters grow as purple/black colonies. E. coli grows colonies with a green sheen.
63
Spirochetes: Sprial shaped bacteria with axial filaments
Borrelia (big size, Leptospira, and Treponema (Boars leaped and tripped on him)
64
False- positive on VDRL
Viral infection (mono, hepatitis), Drugs, Rheumatic fever, Lupus and leprosy (VDRL)
65
Anaplasma species Disease? Transmission and source?
``` Anaplasmosis Ixodes ticks (live on deer and mice) ```
66
Bartonella species Disease? Transmission and source?
Cat scratch disease (immunocompetant), bacillary angiomatosis (immunocompromised) Cat scratch
67
Borrelia bugdorferi DiseasE? Transmission and source?
``` Lyme disease Ixodes ticks (live on deer and mice) ```
68
Borrelia recurrentis Disease? Transmission and source?
Relapsing fever | Louse (recurrent due to variable surface antigens)
69
Campylobacter Disease? Transmission and source?
Bloody diarrhea | Puppies, livestock (fecal oral, ingestion of undercooked meat)
70
Chlamydophila psittaci Disease? Transmission and source?
Psittacosis | Parrots, other birds
71
Coxiella burnetii Disease? Transmission and source?
Q fever | Aerosols of cattle/sheep amniotic fluid
72
Ehrlichia chaffeensis Disease? Transmission and source?
Ehrlichiosis | Ambylomma (lone star tick)
73
Francisella tularensis DiseasE? Transmission and source?
Tularemia | Ticks, rabbits, deer fly
74
Leptospira spp. Disease? Transmission and source?
Leptospirosis | Animal urine
75
Mycobacterium leprae Disease? Transmission and source?
Leprosy | Humans with lepromatous leproy; armadillo (rare)
76
Pasteurella multocida Disease? Transmission and source?
Cellulitis, osteomyelitis | Animal bite, cat, dogs
77
Rickettsia prowazekii Disease? Transmission and source?
Epidemic typhus | Louse
78
Rickettsia rickettsii Disease? Source?
Rocky mountain spotted fever | Dermacentor (dog tick)
79
Rickettsia typhi Disease? Source?
Endemic typhus | Fleas
80
Salmonella Disease? Source?
Diarrhea (which may be bloody), vomiting, fever, abdominal cramps Reptiles and poultry
81
Yersenia pestis Disease? Source?
``` Plague Fleas (rats and prarie dogs are reservoirs) ```
82
Brucella species Disease? Source?
Brucellosis/undulant (rising and falling) fever, spread to reticuloendothelial organs (liver, spleen) causing enlargement Unpasteurized dairy, farm animals

USMLE Step 1-2015 (18 decks)

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