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USMLE Step 1 > Microbiology > Flashcards

Microbiology Flashcards

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USMLE® Step 1 flashcards
1
Q

Cytomegalovirus

A

Herpesvirus family

DS DNA
enveloped (takes from nuclear membrane)
icosahedral

Owl’s eye inclusion (basophilic intranuclear inclusion)

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2
Q

All DNA viruses are ___________ shaped except for _________

A

icosahedral

except pox viruses

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3
Q

Reovirus family

A

DS RNA
naked
icosahedral

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4
Q

Papillomavirus

A

DS DNA
naked
icosahedral

warts

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5
Q

Adenovirus

A

DS DNA
naked
icosahedral

pharyngoconjunctivitis
acute hemorrhagic cystitis
gastroenteritis

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6
Q

Parvovirus

A

SS DNA (only ss DNA virus)
naked
icosahedral

erythema infectiosum

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7
Q

paramyxovirus

A

SS - RNA
enveloped
helical

measles
mumps

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8
Q

flavivirus

A

SS + RNA
enveloped
icosahedral

hep C
yellow fever

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9
Q

Orthomyxovirus

A

SS - RNA
enveloped
helical

influenza

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10
Q

rhabdovirus

A

SS - RNA
enveloped
helical

rabies

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11
Q

togavirus

A

SS + RNA
enveloped
icosahedral

rubella

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12
Q

Hepatitis C family

A

flavivirus

SS + RNA
enveloped
icosahedral

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13
Q

Pseudomonas aeruginosa

A

Gram - ; Oxidase + ; aerobic non-fermenting bacillus

Produce blue-green pigment
Produce fruity odor

Tx fluroquinolones

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14
Q

Haemophilis

A

Gram - bacillus

Requires factors X and V

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15
Q

Gram + , Catalase - , Alpha hemolytic, optochin sensitive coccus

A

Streptococcus pneumoniae

bile soluble

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16
Q

Gram + , Catalase - , Beta hemolytic coccus

A 
Streptococcus agalactiae (bacitracin resistant)
Streptococcus pyogenes (bacitracin sensitive)
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17
Q

Staphylococcus aureus

A

Gram + ; Coagulase + ; Catalase + coccus

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18
Q

Catalase distinguishes these two species

A

Staphylococcus (+)

Streptococcus (-)

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19
Q

Coagulase distinguishes these staph species

A

Coagulase + –> Staph aureus

Coagulase - –> all others (epidermidis, saprophyticus)

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20
Q

Gamma-hemolytic, gram + cocci that grow on bile-esculin agar

A

Enterococci (Group D Strept)

Growth in NaCl: E.faecalis
No growth in NaCl: S. bovis

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21
Q

Alpha hemolytic, optochin resistant, gram + coccus

A

Streptococcus viridans

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22
Q

Alpha hemolytic, optochin sensitive, gram + coccus

A

Streptococcus pneumoniae

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23
Q

Herpes viruses are

A

DS DNA, enveloped, icosahedral

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24
Q

Branching, filamentous bacteria

A

Actinomyces
Nocardia

Both gram positive

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25
Q

Lack a cell wall

A

Mycoplasma, Ureaplasma

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26
Q

Spirochetes

A

Borellia (Giemsa stain)
Leptospira
Treponema

All gram negative

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27
Q

What subunits make up the bacterial ribosome?

A

50s and 30s

40s and 60s in humans

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28
Q

What make spores resistant to dehydration?

A

Keratin-like coat, dipicolinic acid, peptidoglycan

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29
Q

Catalase positive organisms

A 
Nocardia
Pseudomonas
Listeria
Aspergillus
Candida
E.coli
Staphylococci
Serratia
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30
Q

Typical exotoxin diseases (think Gram +)

A

Tetanus, Botulism, diphtheria

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31
Q

Isolated in Bordet-Gengou agar

A

Bordetella pertussis

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32
Q

Virulence factors of staph aureus

A

Protein A: binds Fc of IgG, prevents opson/phago

TSST-1: cytokine release of IL-1, IL-2, IFN-y, TNF-a

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33
Q

IgA protease is used by these organisms and does this

A

S.pneumo, HiB, Neisseria (encapsulated)

Cleaves IgA, colonizes respiratory mucosa

34
Q

Which bugs do not gram stain well?

A 
Treponema
Mycobacteria
Mycoplasma
Legionella
Rickettsia
Chlamydia
35
Q

Virulence factors of Enterotoxigenic E.coli

A

“ETEC”

Heat-labile toxin (LT): + adenylate cyclase, + cAMP, +Cl secretion in gut (pushing out water)
Heat-stable toxin (ST): + adenylate guanase, + gAMP, decrease NaCl resorption in gut (not resorbing water)

36
Q

Isolated in Sabouraud agar

A

Fungi

37
Q

These toxins may cause Hemolytic Uremic syndrome

A 
Shiga toxin (ST) (causes dysentery)
Shiga-like toxin (SLT) (EHEC O157)
38
Q

Virulence factors of Group A Streptococci

A

(Strept pyogenes)

M Protein: prevents phagocytosis
Streptolysin O: degrades cell membrane
Exotoxin A: cytokine release of IL-1, IL-2, IFN-y, TNF-a

39
Q

Isolated in Thayer-Martin agar

A

Neisseria

Contains vancomycin, trimetoprim, colistin and nystatin to inhibit all others

40
Q

What is contained in Chocolate agar?

A

Factors V (NAD+) and X (hematin)

Allows growth of Haemophilis influenzae

41
Q

Isolated in Eaton agar (lipid-rich cell wall)

A

Mycoplasma pneumonia (requires cholesterol)

42
Q

Mechanism of tetanospasmin toxin

A

SNARE inhibition of GABA/glycine –> spasticity, lockjaw

43
Q

Mechanism of botulism toxin

A

SNARE inhibition of ACh –> flaccid, floppy

44
Q

Virulence of Clostridium perfringens

A

Alpha toxin: phospholipase degrades tissue/cell membrane, causes myonecrosis and hemolysis

45
Q

Second most common cause of UTI in young women

A

Staphylococcus saprophyticus

46
Q

Diptheria toxin action on host cell

A

eEF-2 –> inhibits translocation during protein synthesis

47
Q

Cholera toxin action on host cell

A

G-protein (Gs) –> increase cAMP in intestinal epithelium –> diarrhea

48
Q

Pertussis toxin action on host cell

A

G-protein (Gi) –> increases cAMP causing edema, lymphocytosis, increased insulin secretion

49
Q

Pseudomonas toxins action on host cell

A

Exotoxin A: eEF-2 –> inhibit translocation during protein synthesis

Also Exotoxin S, function unknown

50
Q

E. coli heat-labile toxin (LT) action on host cell

A

G-protein (Gs) –> increases cAMP in intestinal epithelium –> diarrhea

51
Q

Botulism toxin action on host cell

A

Neurotoxin prevents neurosecretory vesicles from fusing with synaptic membranes and releasing acetylcholine

52
Q

Shiga toxin action on host cell

A

Inhibit 60s ribosomal subunit –> decreasing protein synthesis

53
Q

Tetanus toxin action on host cell

A

Neurotoxin that inhibits release of inhibitory neurotransmitters glycine and GABA

54
Q

What are the positive sense RNA viruses?

A 
Retrovirus
Togavirus
Flavivirus
Coronavirus
Hepevirus
Calicivirus
Picornavirus
55
Q

What are the DNA viruses?

A 
H - Hepadna
H - Herpes
A - Adeno
P - Pox
P - Parvo
P - Papilloma
P - Polyoma
56
Q

What is the only ds RNA virus?

A

Reovirus

57
Q

What are the killed vaccines?

A

R - rabies
I - influenza
P - Polio (salk)
A - Hep A

58
Q

What are the subunit vacines?

A

Hep B Virus

HPV

59
Q

Where do DNA viruses replicate?

A

Nucleus

–> except poxvirus

60
Q

Where to RNA viruses replicate?

A

Cytoplasm

–> except influenza and retrovirus

61
Q

Virulence factors of Pseudomonas aeruginosa

A

Exotoxin A (protein synthesis inhibition)
Elastase (degrades elastin, needed by blood vessels)
Phospholipase C (degrades cell membranes)
Pyocyanin (generates reactive oxygen species)

62
Q

Lancet-shaped gram-positive organisms

A

Strep pneumo

63
Q

Naked DNA Viruses

A

Adenovirus, Polyoma, Papilloma, Parvovirus

64
Q

DNA Viruses (enveloped)

A

Poxvirus, Herpesvirus, Hepadna

65
Q

RNA Viruses (enveloped)

A

Paramyxovirus, Rhabdovirus, Orthomyxovirus, Coronavirus, Flavivirus, Togavirus

66
Q

Naked RNA Viruses

A

Reovirus, Calcivirus, Hepevirus, Picornavirus

67
Q

Congenital infection resulting in diffuse intracranial calcifications, hydrocephalus, chorioretinitis, CSF pleocytosis or elevated CSF protein

A

Toxoplasmosis

68
Q

Congenital infection resulting in skeletal abnormalities, pseudoparalysis, rhinitis, macropapular rash

A

Syphilis

69
Q

Congenital infection resulting in heart disease, sensorineural hearing loss, cataracts, glaucoma

A

Rubella

70
Q

Congenital infection resulting in hepatosplenomegaly, sensorineural hearing loss, thrombocytopenia, periventricular intracranial calcifications, microcephaly

A

CMV

71
Q

Congenital infection resulting in Conjunctivitis, thrombocytopenia, elevated liver enzymes, mucocutaneous vesicles/scarring

A

Herpes simplex virus

72
Q

Hep A family, transmission, disease character

A

Picornavirus (RNA), fecal-oral, mild acute disease (IgM-HAV)

73
Q

Hep B family, transmission, disease character

A

Hepadnavirus (DNA), sex/parenteral, acute/occassional chronic, HBsAg/IgM-HBcAg

74
Q

Hep C family, transmission, disease character

A

Flavivirus (RNA), parenteral/IVDU/sex, acute –> chronic, Ab to HCV

75
Q

Hep D family, transmission, disease character

A

Delta (circular RNA), parenteral/sex, coinfection HBV, Ab to HDV + HBsAg

76
Q

Hep E family, transmission, disease character

A

Hepevirus (RNA), Fecal-oral, mild unless pregnant, Ab to HEV

77
Q

Virulence factors of Strep pneumo

A

Polysaccaride capsule, prevents phagocytosis, more than 90 types of capsule antigens

Also: IgA protease, adhesins, pneumolysin

78
Q

Characteristics of Histoplasma capsulatum

A

Ovoid cells within macrophages
Dimorphic fungus found in soil, bird, bat droppings
Mississippi and Ohio River basins
Forms granulomata, causes lymphadenopathy, hepatosplenomegaly, acute pulmonary disease

79
Q

Characteristics of Coccidioides immitis

A

Spherules packed with endospores
Pulmonary disease in immunocompetent
Southwest US

80
Q

Characteristics of Cryptococcus neoformans

A

Budding yeast with thick capsule found in soil with bird/pigeon droppings
Meningoencephalitis and pulmonary disease in immuocompromised

81
Q

Characteristics of candida

A

Yeasts that form pseudohyphae

82
Q

Characteristics of Aspergillus

A

Septate hyphae with V-shaped branching

Pulmonary disease in immunocompromised

USMLE Step 1 (5 decks)

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