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USMLE Step 1 > Micro > Flashcards

Micro Flashcards

1
Q

What is the stain used to visualize legionella?

A

Silver Stain

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2
Q

Is nocardia or actinomyces acid fast?

A

Nocardia

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3
Q

What agar is used for C. diptheria?

A

Cysteine - Tellurite agar (black colonies)

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4
Q

What do E. coli look like on EMB agar?

A

Dark purple colonies with green metalic sheen

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5
Q

What are common encapsulated bugs?

A 
S. Pneumoniae
H. Flu
N. Meningitides
E. Coli
Salmonella
K. pneumoniae
GBS
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6
Q

Is listeria catalase positive?

A

Yes

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7
Q

What are some weird urease + bugs?

A

Cryptococcus, S. Epidermidis, S. Saprophyticus

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8
Q

What bacteria produce a red pigment?

A

S. Marcescens

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9
Q

What bacteria express IgA protease?

A

SHiN bacteria

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10
Q

How does shiga toxin inactivate 60S ribosome?

A

Removes adenine from rRNA

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11
Q

Does heat stabile toxin decrease reabsorption or increase secretion?

A

Decreases reabsorption of NaCl and H2O in the gut

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12
Q

How does B. Anthracis edema factor work?

A

Mimics adenylate cyclase

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13
Q

How do the toxins of V. Cholera and B. Pertussis differ?

A

Cholera - permanently activates Gs

Pertussis - Disables Gi

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14
Q

What toxins are encoded in a lysogenic phage (specialzied transduction)?

A 
ABCDE:
shigA like toxin
Botulinum toxin
Cholera toxin
Diptheria toxin
Erythrogenic toxin of S. pyogenes
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15
Q

Are viridans group strep bile soluble or insoluble?

A

Bile insoluble

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16
Q

What kind of hemolysis does L. monocytogenes exhibit?

A

Beta hemolysis (and tumbling motility)

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17
Q

Which strain of viridans group strep causes subacute bacterial endocarditis?

A

S. Sanguis (makes dextrans which bind to fibrin-platelet aggregates)

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18
Q

What factor is produced by Group B Strep?

A

CAMP factor - enlarges the area of hemolysis formed by S. Aureus.

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19
Q

Which bacterium has metachromatic blue-red granules?

A

C. Diptheriae

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20
Q

What bacterial spores are found in soil?

A

Antharax, C. perfringens, C. tetani

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21
Q

How does one differentiate atropine poisoning and botulism?

A

Atropine only blocks muscarinic receptors, so it wouldn’t have skeletal muscle weakness

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22
Q

What are the 3D’s of botulism?

A

Diplopia, Dysphagia, Dysphonia

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23
Q

What two types of poisoning can B. cereus cause?

A

Nausea/Vomiting - 1-5 hr onset (cerulide toxin)

Diarrheal - 8-18 hr onset

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24
Q

What forms the rocket tails of listeria?

A

Actin polymerization

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25
Q

What gram positive produces LPS?

A

Listeria

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26
Q

What granulomatous disease might show false - PPD?

A

Sarcoidosis, use IFN-gamma release assay

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27
Q

What is the key virulence factor in Mycobacterium?

A

Cord factor - causes serpentine growth pattern. Inhibits Mphage maturation

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28
Q

What is the treatment of leprosy?

A

Tuberculoid - Dapsone, Rifampin for 6 months

Leparomatous - Dapsone, Rifampin, clofazimine for 2-5 yrs

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29
Q

What enzyme does E. coli produce?

A

Beta galactosidase

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30
Q

What is Fitz-Hugh-Curtis syndrome?

A

Inflammation of the liver capsule. Gonoccoci

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31
Q

What bacteria can provide the needed factors for H. flu?

A

S. Aureus

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32
Q

What is used for H. flu mucosal infections?

A

Amoxicillin

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33
Q

What electrolyte abnormality is seen with Legionella?

A

Hyponatremia

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34
Q

What media is needed to culture legionella?

A

Charcol-yeast extract with Fe and Cysteine

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35
Q

What is a common finding in malignant otitis externa in diabetics?

A

Granulation tissue in the ear cannal

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36
Q

How does EPEC cause disease?

A

Adheres to apical intestinal surface and flattens villi causing malabsorption (pediatric diarrhea, rx with quinolones)

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37
Q

What is a key finding for EHEC?

A

Does not ferment sorbitol. Also usually no fever and no PMNs in stool b/c it is not invasive

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38
Q

What are the 4 A’s of klebsiella?

A

Aspiration, Abscess (lung, liver), Alcoholics, diAbetics

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39
Q

Do antibiotics help in Shigella? Salmonella?

A

Shigella - shorten duration of organism excretion

Salmonella - May prolong fecal excretion of organisms

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40
Q

What is the difference in inflammatory response between shigella and salmonella?

A

Shigella - PMN response

Salmonella - Monocytic response

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41
Q

Does shigella have animal reservoirs?

A

No

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42
Q

What temp does campylobacter grow at?

A

42 C

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43
Q

What temp does Yersinia grow well at?

A

Less than body temp

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44
Q

Which spirochete can be visualized with aniline dyes?

A

Borrelia

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45
Q

What population is leptospirosis common among?

A

Sufurs

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46
Q

What is Weils disease?

A

Icterohemorrhagic leptospirosis, jaundice, azotemia, hemorrhage, anemia

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47
Q

What stage of syphilis has a rash?

A

Secondary

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48
Q

What is the vector of Borellia recurentis?

A

louse

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49
Q

What is the disease and vector for R. Prowazekii?

A

Epidemic Typhus - Louse

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50
Q

What is the disease and vector for R. typhi?

A

Endemic typhus - Fleas

51
Q

What drug are ehrlichia and anaplasma resistant to?

A

Chloramphenicol

52
Q

What type of discharge is seen with gardnerella vaginalis?

A

Gray/fishy vaginal discharge

53
Q

What disease does brucella abortus cause?

A

Caseating granulomas and mild FUO. Veterenarians and ranchers

54
Q

What bug causes localized skin infection in meat and fish handlers?

A

Erysipelothrix rhusiopathiae

55
Q

What disease causes black-based ulcers with epitrochlear LAD?

56
Q

What disease can systemic mycoses mimic?

A

TB (granuloma formation) but no person-person dissemination

57
Q

What type of lesion is seen in the brain with crytococcus?

A

Soap Bubble

58
Q

What do P. Jiroveci look like?

A

Disc-shaped yeast on methenamine silver stain

Honeycomb on HnE

59
Q

What drugs are used for P. jiroveci?

A

Treatment: TMP/SMX, Pentamidine
Prophylaxis: Above + dapsone, atovaquone

60
Q

What are the treatments for Sporothrix?

A

Itraconazole or KI

61
Q

What can be used to treat cryptosporidium?

A

Nitazoxanide

62
Q

How do you diagnose cryptosporidium?

A

Oocysts are acid-fast

63
Q

What is the classic triad of congenital toxo?

A

Chorioretinitis, hydrocephalus, intracranial calcifications

64
Q

What drugs can be used to treat E. histolytica?

A

Metronidazole or iodoquinol

65
Q

What organism causes quartan malaria?

A

P. malariae

66
Q

What cells clear plasmodium infected RBCs?

67
Q

What two forms of plasmodium can be seen on a smear?

A

Schizont containing merozoites or trophozoite ring form

68
Q

What is the treatment of malaria?

A

Chloroquine (blocks heme polymerase)
Resistant: mefloquine, atovaquone/proguanil
Life threatening: Quinidine (test G6PD)
Vivax/Ovale: primaquine

69
Q

What is the treatment of babesia?

A

Atovaquone + Azithromycin

70
Q

What is the classic finding on RBC smear for babesia?

A

Maltese Cross. Asplenia increases risk of severe disease

71
Q

What is used to treat T. cruzi?

A

Benznidazole or nifurtimox

72
Q

What is used to treat Leishmani donovani?

A

Ampho B or Sodium Stibogluconate

73
Q

What is used to diagnose leishmania?

A

See Mphages containing amistigotes

74
Q

How is T. vaginalis transmited?

A

Sexual, cannot exist outside human b/c it can’t form cysts

75
Q

What is used to treat pinworms, Ascaris, Ancyclostoma, and Necator?

A

Bendazoles or pyrantel pamoate

76
Q

What can the pain of S. stercoralis mimic?

A

Peptic ulcers

77
Q

What are the skin findings for onchoceriasis?

A

hyperpigmented black spots

78
Q

What is used to treat S. Stercoralis?

A

Ivermectin or albendazole

79
Q

What is used to treat filariasis?

A

Diethylcarbamazine

80
Q

What does toxocara canis cause?

A

Visceral larva migrans (fecal-oral tranmission)

81
Q

What is used to treat T. solium, D. latum, schistosoma and Clonorchis sinensis?

A

Praziquantel

82
Q

What is used to treat neurocysticercosis and E. granulosum?

A

Albendazole

83
Q

What causes neurocysticercosis?

A

Ingestion of tapeworm eggs

84
Q

What hosts schistosoma?

A

Fresh water snails

85
Q

What fluke causes biliary tract inflammation?

A

Clonorchis sinesis

86
Q

What shicstosomes infect the liver/portal tract?

A

S. mansoni and S. japonicum (pipe-stem fibrosis)

87
Q

What is recombination?

A

Occurs in non-segmented genomes

88
Q

What is reasortment?

A

Occurs in segmented genomes

89
Q

What is complementation?

A

1 of 2 viruses infecting a cell has a mutation resulting in a on-functional protein provided by the other virus

90
Q

Which vaccines are live-attenuated?

A

Smallpox, Yellow Fever, VZV, Sabin, MMR, Flu (nasal)

91
Q

Which vaccines are killed?

A

Rabies, Flu (injected) Salk, HAV

92
Q

Which vaccines are recombinant?

A

HBV and HPV

93
Q

Which three DNA viruses have non-linear genomes?

A

Papiloma, Polyoma, and Hepadnavirus

94
Q

Which DNA virus replicates in the cytoplasm?

95
Q

What are HHV-4 and HHV-5?

A 
HHV4 = EBV
HHV5 = CMV
96
Q

What are the two polyoma viruses?

A

JC - causes PML in HIV patients

BK virus - targets kidneys in transplant patients

97
Q

Where is EBV immortalized? CMV?

A

EBV - Infected B cells

CMV - monocytes

98
Q

What is the rash of roseola (HHV-6)?

A

Diffuse and macular following high fevers

99
Q

What nuclear inclusions do infected cells with herpesvirsues have?

A

Cowdry Type A on a Tzank smear

100
Q

Which viruses transcribe a polyprotein that is cleaved?

A

ssRNA + viruses

101
Q

Which RNA viruses have circular genomes?

A

Arenaviruses (Lasa)
Bunyaviruses (Hanta)
Delta virus

102
Q

Which viruses are segmented?

A 
BOAR
Bunyaviruses
Orthomyxoviruses
Arenaviruses
Reovirus
103
Q

What is the mechanism of rotavirus diarrhea?

A

Villus destruction and atrophy - decreased Na absorption, loss of K.
Vaccinate infants

104
Q

How does the live-attenuated flu vaccine work?

A

It is temp sensative so can replicate in nose but not in lung

105
Q

What is a blueberry muffin rash of rubella indicative of?

A

Extramedulary hematopoeisis

106
Q

What protein do all paramyxoviruses contain?

A

F protein which causes respiratory epithelial cells to fuse and form MNGCs (blocked by Pavalizumab)

107
Q

When is a Warthin-Finkeldey giant cell seen? (MNGC with eosinophilic cytoplasm and nuclear inclusion bodies)

A

In measels infection, particularly the rare giant cell pneumonia sequelae

108
Q

What vaccine can cause post-vaccination lymphadenitis?

109
Q

What is worse for HDV? Superinfection or Coinfection?

A

Superinfection is worse, shorter incubation as well

110
Q

What diagnostic test is used for the various phases of HBV?

A

Incubation: HBsAg
Prodrome/Acute Disease: HBsAg or anti-HBc
Early Convalescence: Anti-HBc
Late Convalescence: Anti-HBs or Anti-HBc

111
Q

What are the functions of gp41 and gp120?

A

gp120 - attachment to CD4+ cell

gp41 - fusion and entry

112
Q

What receptors does HIV bind to?

A

CCR5 (early) or CXCR4 (late) on T cells

CCRF and CD4 on Macrophages

113
Q

When are HIV tests usually falsely negative?

A

In the first 1-2 months of HIV infection

114
Q

Why are HIV tests often falsely positive in newborns of HIV infected mothers?

A

anti-gp120 crosses the placenta

115
Q

How many antigens must be positive on western blot?

A

2/3, otherwise use PCR to confirm

116
Q

What supplement is required to grow F. tularensis?

A

Cysteine + blood agar. VERY DANGEROUS highly infective

117
Q

What are the types of tularemia?

A

Ulceroglandular - ulcer + nodal swelling
Pneumonia - inhalation or blood stream
Oculoglandular - direct into eyes
Typhoidal - from ingestion

118
Q

What are the reservoirs for F. tularensis?

A

Rabbits and squirrels as well as ticks

119
Q

What is used to treat tularemia?

A

Gentamicin, Streptomycin, doxycycline (intracellular parasite)

120
Q

How does one contract Brucella?

A

Contact with live-stock or placentas (likes erythritol)
Ingestion of milk products
Aerosolization

121
Q

What is brucellosis?

A

Undulating fever (peaks in evening), weakness, anorexia

122
Q

What do you use to treat brucellosis?

A

Doxycycline + streptomycin/gentamicin/rifampin

Cattle are imunized

123
Q

What drug class is Y. enterocolitica resistant to?

A

Cephalosporins! Use Fluoroquinolone or TMP-SMX

USMLE Step 1 (4 decks)

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