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USMLE S1 > Microbiology > Flashcards

Microbiology Flashcards

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USMLE® Step 1 flashcards
1
Q

virulence factor M protein function

A

molecular mimicry, similar epitope to human protein. ?AI response of ARF. group A streptococcus

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2
Q

Q fever - what bug?

A

coxiella burnetii

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3
Q

McConkey’s Agar cultures….

A
  • Klebsiella*
  • E Coli*
  • Enterobacter*

Bile salt-containing which inhibits growth of most gram +ve organisms

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4
Q

2 topical antifungals for infection?

A

itraconazole, fluconazole

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5
Q

VDRL tests for what disease? what is the sensitivity?

A

syphillis 80%

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6
Q

cell wall component unique to Gram -ve bacteria?

A
  • endotoxin/LPS
  • porin
  • periplasmic space
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7
Q

food poisoning giving constipation followed by a flaccid paralysis suggets?

A

clostridium botulinum

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8
Q

Monospot test +ve suggests what?

A

heterophile antibodies present in serum, represents EBV (HHV-4) infection.

Important negative in suspected CMV (HHV-5)

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9
Q

parainfluenza, mumps, RSV, metapneumovirus, measles are all…

A

paramyxoviridae

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10
Q

hippie mother, orchitis and aseptic meningitis, followed by pancreatitis should suggest…

A

Mumps

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11
Q

the transfer of vancomycin resistance from enterococcus to other bacteria occurs through which genetic process? describe…

A

transposition gene flanked by two ‘transposon’ sequences in a plasmid that can be cleaved and integrated into bacterial chromosomes

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12
Q

unique bacterial structure of Bacillus anthracis

what is the anthracis toxin and how does it work

A

only bacterium with a polypeptide (D-glutamate) capsule

oedema toxin - mimics adenyl cyclase (increasing cAMP) leading to haemorrhage (haemorrhagic mediastinitis) and oedema (bloody pleural effusion, shock)

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13
Q

myobacterium sulfatide is what? function?

A

surface glycolipid prevents phagocytosis - granuloma formation

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14
Q

vibrio is…

A

enteric gram -ve bacillus

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15
Q

pityriasis versicolor is caused by which bug?

A

malassezia spp. not strictly a dermatophyte, despite being called tinea sometimes. malassezia is a yeast-like fungus

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16
Q

what is going on?

what else is this baby at risk of? (4)

A

congenital rubella syndrome

‘blueberry muffin’ - dermal extramedullary haematopoesis in response to infection. Confirm with serum IgM vs Rubella (cannot be mother’s)

deafness, blindness/cataracts, microcephaly and congenital cardiac abnormality

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17
Q

CSF findings in viral meningitis

(OP, cell type, protein, glucose)

A

OP - normal

cell type - lymphocytes

protein - normal/up

glucose - normal

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18
Q

genital ulcer - painless, progressive red ulcerative leasions with a wavy border (serpinginous). No lymph nodes.

diagnosis (bug)? diagnostic test?

A

granuloma inguinale (donovanosis) - Klebsiella granulomatis

gram strain and culture (hard to get), biopsy with looking for Donovan bodies.

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19
Q

What medium is used for Corynebacterium dyptheriae?

A

Cysteine-Tellurite agar

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20
Q

what are three mechanisms for aminoglycoside resistance?

A

aminoglycoside-modifying enzymes

mutated ribosomal subunit &/or porin proteins

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21
Q

staphylococcus aureus produces what colour pigment?

A

yellow aureus = ‘gold’

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22
Q

bordatella is…

A

respiratory gram -ve bacillus

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23
Q

clostridium is…

A

gram +ve bacillus

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24
Q

does and endotoxin or an exotoxin have greater antigenicity? (i.e. versus which do we make antibodies)

A

exotoxin - induces high-titre antibodies called antitoxins

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25
Q

parasite association haematuria, SCC bladder

A

schistosoma haematobium

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26
Q

which type of bacteria have an outer membrane?

A

Gram -ve

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27
Q

neonatal - HSM, jaundice, petichiae/purpura, chorioretinitis, SFGA & microcephaly

suggests what congenital infection? what is at risk? Rx?

A

congential CMV

most newborns will be asymptomatic but 15% will develop progresive senorineural hearing loss.

Ganciclovir - prevent hearing loss and dev delay

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28
Q

which HHV - herpetic whitlow, herpes labialis, keratoconjunctivitis?

A

HHV-1

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29
Q

H pylori treatment?

A

triple therapy

omeprazole, amoxicillin

& either metronidazole or clarithromycin

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30
Q

how would you get campylobacter jejuni? (2)

A

faeco-oral transmission from:

  1. domestic animals
  2. undercooked food/poultry
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31
Q

what bug requires factors X and V for growth?

A

Haemophilius influenzae

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32
Q

what is prostitute’s pupil?

A

Argyll-Roberson pupil - constricts to accommodation but not light reaction sign of tertiary neurosyphillis

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33
Q

which bug is likely to produce a biofilm around a catheter or prosthetic device in situ?

A

S epidermidis

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34
Q

pseudomonas aeruginosa produces what colour pigment?

A

blue-green

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35
Q

catalase tests between which gram +ve bacteria? which is catalase +ve?

A

staphylococcus and streptococcus/enterococcus staphylococcus is catalase +ve

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36
Q

classification of parvovirus B19?

A

nonenveloped, single-stranded DNA virus

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37
Q

salmonella vs shigella flagella?

A

salmonella (salmon swim)

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38
Q

what infection are cryogolbulins commonly associated with?

A

HCV

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39
Q

a double-stranded, non-enveloped DNA virus causing hydrops fetalis (& IUD) or aplastic crisis in sickle cell disease is…

A

parvovirus B19

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40
Q

which are the medically important paramyxoviridae?

A

PaRaMyxovirus

P - parainfluenza

R - RSV treat with Ribavirin

M - mumps, measels

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41
Q

elderly meningitis bugs (2)

A

S pneumoniae, Listeria

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42
Q

group B, beta-haemolytic strep is…

A

strep agalactiae

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43
Q

most common complication of this?

A

post-herpetic neuralgia

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44
Q

enterococcus is…

A

gram +ve coccus

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45
Q

what bugs are positive for haemadsorption on blood cell culture?

A

Influenza and parainfluenza - they have haemaglutinin (H) surface glycoprotein that have high affinity for erythrocytes

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46
Q

what bugs are associated with dog bites?

A

Pasteurella multocida (mouse-like odour on culture)

Streptococci

Staph aureus

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47
Q

what are the mechanisms of action for ribavirin?

A

overall = interferes with duplication of viral genes

ribavirin becomes ribavirin mono-/di-/tri-phosphate in the cell

  • substitutes into viral RNA causing RNA-dependent viral gene replication hypermutation which is lethal.
  • depletes intracellular GMP/GTP
  • directly interferes with viral RNA-dependent RNA polymerase
  • immunomodulation favouring CD8+ cytotoxic cells
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48
Q

bugs for PID

A

Chlamydia trachomatis (subacute, often undiagnosed)

neisseria gonorrhoeae (acute)

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49
Q

what is the unique resistance mechanism to quinolones?

A

mutated DNA gyrase

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50
Q

Grma -ve bacillus, non lactose fermenting, oxidase -ve.. what’s left? (4) how to tell apart?

A

salmonella, proteus (makes H2S) shigella, yersinia (no H2S)

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51
Q

gam +ve rod with metachromatic granules and +ve Elek test

A

corynebacterium diptheriae

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52
Q

high fever in infant (6 - 36 months) followed by diffuse maular rash starting on the trunk and spreading to the head and face suggests what disease?

What bug?

A

roseola infantum (erythema subitum)

HHV-6 (less commonly HHV-7)

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53
Q

classification of HSV?

A

double-stranded DNA, enveloped

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54
Q

what bug is this? Most common disease caused in immunocompromise?

Rx (3)?

A

Cryptococcus neoformans

fungal meningioencephalitis

amphotericin B and flucytosine (followed by fluconazole if meningitis)

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55
Q

yersinia is…

A

enteric gram -ve bacillus

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56
Q

time frame of N and V with bacillus cereus ingestion?

A

1 - 5 hours (preformed cereulide toxin)

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57
Q

major complication of neonatal N gonorrhoeae infection? Rx?

A

conjunctivitis –> blindness erythromycin eye drops

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58
Q

what is the correct antimicrobial for and when do you start prophylaxis in HIV against:

  • PCP
  • toxoplasma gondii
  • mycobacterium avium complex
  • Histoplasma capsulatum​​
A
  • CD4+ < 200 - co-trimoxazole
  • CD4+ < 100 - co-trimoxazole
  • CD4+ < 50 - azithromycin
  • CD4+ < 150, endemic area - itraconazole
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59
Q

listeria Rx

A

ampicillin

(+ gentamycin if immunocompromised)

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60
Q

bacillus cereus diarrhoea has what appearance?

A

8 - 18 hours following ingestion, watery non-bloody diarrhoea with GI pain

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61
Q

an asthmatic/CF patient with eoisinophilia, elevated serum IgE and recurrent lung infiltrated leading to bronchiectasis

disease?

bug?

A

allergic broncopulmonary aspergillosis

aspergillus fumigatus

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62
Q

genital ulcer - deep, purulent, painful. suppurative lymphadenitis

what disease? diagnostic test?

A

chancroid - haemophilus ducreyi

Gram stain and culture of swab. PCR.

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63
Q

what bug likely causes epiglotitis?

what is it’s major virulence factor and target of its vaccine?

A

HiB

polyribosylribitol phosphate

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64
Q

definitive diagnosis of HSV-1 encephalitis?

A

CSF PCR

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65
Q

major staph epidermidis virulence factor

A

exopolysaccheride secretion forming biofilm - typically causes foreign body infection such as IV catheter or ventriculoperitoneal shunt

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66
Q

which gram -ve, oxidase +ve organism grown in alkaline medium?

A

Vibrio

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67
Q

ventilator-associated pneumonia or contact lens-associated keratitis is usually which bug?

A

pseudomonas aeruginosa

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68
Q

this is specific finding of what childhood virus?

What are these called?

If this was on the palate, how does the answer change?

A

Measles

Koplik spots

Would be Rubella (german measles), Forchheimer spots. Lymphadenopathy more likely

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69
Q

top 3 bugs for UTI

A

E coli

Staph saprophyticus (sexually active)

Klebsiella (urease-positive so assoc with MAP stones)

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70
Q

PCP pneumonia treatment & prophylaxis?

A

Rx - co-trimoxazole (TMP-SMX), inhaled pentamidine, atovaquone

prophylaxis - 1st line = co-trimoxazole, sulfa allergy = dapsone
(when HIV CD4+ T cell count <200 cells/mm^3)

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71
Q

erythema nodosum/multiforme, with arthralgia and risk of meningitis (fungus)?

A

coccidioidomycosis

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72
Q

what receptor does EBV use to enter cells?

A

CD21

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73
Q

cellular mechanism of pertussis toxin

A

inhibition of Gi, disinhibition of cAMP production in the cell, prevents successful phagocytosis

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74
Q

empiric treatment of CoNS until sesnitivities are back from the lab? what is this bug likely to be resistant to?

A

vancomycin - blocks gram +ve wall synthesis without being pen/cef class

methcillin-resistance, with mecA gene package (alteration to PBPs) - accompanied by resistnace to fluoroquinolones and clindamycin

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75
Q

What bug produces biofilms in otitis media?

A

Haemophilius influenza (nontypable)

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76
Q

shigella is…

A

enteric gram -ve bacillus

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77
Q

staphylococcus is…

A

gram +ve coccus

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78
Q

pseudomonas is…

A

enteric gram -ve bacillus

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79
Q

virulence factor protein A function?

A

binds Fc region of IgG preventing opsonisation or phagocytosis.. S aureus

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80
Q

Propionobacterium acnes is…

A

gram +ve bacillus

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81
Q

which leprosy has a predominantly cell-mediated (Th1) response?

A

tuberculoid

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82
Q

legionella is…

A

respiratory gram -ve bacillus

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83
Q

Gram -ve bacillus, non lactose fermenting, oxidase +ve..

A

pseudomonas

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84
Q

INF-gamma primarily secreted by what cells? function (4)?

A

Th1 lymphocytes

increase macrophage phagocytosis and NK cell killing. Increase MHC expression on all cell types. Inhibit Th2 cell proliferation.

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85
Q

what bugs are associated with human bites?

A
  • Staphylococcus aureus;* Streptococci
  • Eikenella corrodens*

and a mixture of other anaerobes

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86
Q

proteus, cryptococcus, h pylori, ureaplasma, klebsiella, s epidermidis, S saprophyticus are all…

A

urease-positive organisms

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87
Q

chlamydia is…

A

pleomorphic without cell wall

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88
Q

3 bugs for HIV-associated oesophagitis? defining finding on OGD

A
  1. candida albicans - pseudomembranes
  2. HSV-1 - punched-out ulcers
  3. CMV - linear ulceration
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89
Q

campylobacter is…

A

enteric gram -ve bacillus

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90
Q

is endotoxin or exotoxin(s) more heat-stable?

A

endotoxin.. induces fever so must be fine in heat

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91
Q

granulomatosis infantiseptica is caused by what bug?

A

listeria monocytogenes

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92
Q

Rocky Mountain Spotted Fever - what bug? How is it spread?

A

rickettsia rickettsii dog tick

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93
Q

bronchiolitis in under 2 y/o - most common bug?

A

RSV

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94
Q

cell wall component unique to Gram +ve bacteria?

A

lipoteichoic acid

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95
Q

Mycobacterium is…

A

gram +ve bacillus

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96
Q

in a newborn - chorioretinitis, hydrocephalus and intracranial calcifications

A

congenital toxoplasmosis

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97
Q

give a few (5 classes) Abx good for pseudomonas

A

(Tazocin) piperacillin

(3-4th gen cephalosporin) cefepime, ceftazidime

(aminoglycosides) amikacin, gentamicin

(fluoroquinolones - for RTI) cipro, levofloxacin not moxi

(carbapenems) meropenem

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98
Q

a dilated cardiomyopathy, apical atrophy, megacolon and megaoesophagus suggests what bug? disease called?

A

trypanosoma cruzi American trypanosomiasis/Chagas disease

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99
Q

diagnostic test for histoplasmosis?

A

blood/urine antigen

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100
Q

salmonella is…

A

enteric gram -ve bacillus

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101
Q

what receptor does HIV use to enter cells?

A

CD4

then needs CXCR4 or CCR5

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102
Q

which are the bugs that pass from mother to child?

A

ToRCHHeS

Toxo, rubella, CMV, HIV, Herpes (HSV-2), syphilis

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103
Q

aerobic gram +ve bacillus? (2)

A

listeria bacillus

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104
Q

risus sardonicus is associated with which condition? which bug?

A

tetanus clostridium tetani

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105
Q

mycoplasma is…

A

pleomorphic without cell wall

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106
Q

multinucleated trophozoite found in stool/cysts

A

giardia lamblia

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107
Q

what is appropriate CMV prophylaxis in post-lung transplant patients?

what family is CMV and what is the viral classification?

A

valganciclovir

Herpes virus - DNA, double stranded, enveloped

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108
Q

bacillus is…

A

gram +ve bacillus

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109
Q

urease-positive organisms are associated with what condition?

A

MAP nephrolithiasis

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110
Q

species responsible for hot tub folliculitis?

A

pseudomonas aeruginosa

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111
Q

novobiocin tests between which bacteria? which is sensitive?

A

staph epidermidis and staph saprophyticus staph epidermidis is sensitive

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112
Q

what is the mechanism for rifamycin resistance?

A

mutated RNA polymerase

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113
Q

what are the mechanism of actions of the antimycobacterial drugs?

side effects?

A

R - mRNA synthesis - GI, rash, red (orange) secretions, cytopenia

I - mycolic acid (cell wall) synthesis inhibition - neurotoxic (B6 adjunt) & hepatotoxic

P - unclear - hepatotoxic & hyperuricaemia

E - inhibition of arabinosyl transferase (?) - optic neuropathy

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114
Q

botulinum toxin - mechanism of action and 4 D symptoms

A

SNARE protease, inhibiting ACh release at NMJ. Flaccid paralysis. D - diplopia, dysphagia, dysarthria, dyspnoea

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115
Q

What bug produces biofilms on contact lenses?

A

Pseudomonas aeruginosa

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116
Q

decreased gastric acidity (increased pH) makes you more sensitive to which gram -ve organisms?

A

shigella and vibrio

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117
Q

CSF findings in fungal meningitis

(OP, cell type, protein, glucose)

A

OP - up

cell type - lymphocytes

protein - up

glucose - down

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118
Q

gram -ve bacillus, lactose fermenting bacteria are… (3)

A

tested using McConkey’s McConKEE K - Klebs E - E Coli E - Enterobacter

119
Q

for Lyme disease features, what does FACE stand for?

A

F - facial nerve palsy (Bell’s) A - arthralgia C - carditis E - erythema multiforme

120
Q

what CD4+ cell count inidcates progression to AIDS?

A

< 200 CD4+ cells/mm^3

(500 - 1500)

121
Q

neisseria is…

A

gram -ve coccus

122
Q

what bugs can cause impetigo?

A

staph aureus

group A strep (Strep pyogenes)

123
Q
A
124
Q

giardia lamblia treatment?

A

metronidazole

125
Q

what receptor does CMV use to enter cells?

A

integrins (heparin sulphate)

126
Q

what extracellular molecule does strep viridans have the capacity to adhere to? how is this clinically relevant?

A

fibirin-platelet aggregations

Strep viridans only causes endocarditis on previously damaged valves. Staph aureus can adhere to undamaged valve.

127
Q

streptococcus is…

A

gram +ve coccus

128
Q

Kala-azar is also known as? bug? blood findings?

A

visceral leishmaniasis leishmania donovani - pancytopenia

129
Q

virulence factor IgA protease function?

A

cleave IgA, allowing mucosal colonisation S pneumoniae, H influenzae, N meningitidis

130
Q

on VE - thin white, fishy discharge with no erythema

Clue cells present, alkalinisation

disesae? Bug? Rx?

A

bacterial vaginois - Gardnerella vaginalis

metronidazole

131
Q

what receptor does parvovirus B19 need to enter cells?

A

P antigen (globoside) expressed on erythrocytes

132
Q

during infectious mononucleosis, what advice is given to patients?

what bug?

what medication should be avoided?

A

no contact sport - risk of splenic rupture

Ebstein-Barr virus (HHV-4)

Amoxicillin - associated rash

133
Q

on VE - cervical inflammation, frothy, foul smelling, yellow discharge

HVS - motile bugs, alkalinisation

Rx?

A

trichomonas vaginalis vaginitis

metronidazole, treat partner

134
Q

how to tell N meningitidis from N gonorrhoeae?

A

maltose test +ve = meningitidis -ve = moraxella or N gonorrhoeae

135
Q

how to shigella and salmonella invade the GI tract?

A

through M cells in the Peyer patches

136
Q

first line treatment for any leprosy? what is added for lepromatous leprosy?

A

dapsone and rifampin add clofazimine

137
Q

What bug produces biofilm on dental plaques?

A

Strep viridans (mutans and sanguinis)

138
Q

what is the mechanism of action for acyclovir?

A

nucleoside ananlog (dGTP)

acyclovir is activated into active compound, incorporated into DNA through viral DNA polymerase

when incorporated, DNA polymerisation terminates and replication fails.

139
Q

what receptor does rabies use to enter cells?

A

nAChR

140
Q

GI bugs with a very low ID(50) - infectious dose required to cause disease in 50% of affected individuals. (4)

A

Shigella

Giardia

Campylobacter jejuni

Entamoeba histolytica

roughly 10 - 1000 organisms can cause disease (so 10^2-10^4)

141
Q

which leprosy is lethal?

A

lepromatous

142
Q

anaerobic gram +ve bacillus? (2)

A

clostridium propionibacterium

143
Q

trophozoite with engulfed RBCs

A

entamoeba histolytica

144
Q

what does capsofungin do?

when is it used?

A

non-competitive inhibitor of beta-glucan synthase

candida resistant to -azoles

145
Q

what does viral RNase H do?

A

removes viral RNA primer from newly synthesized DNA

blocking RNase is useful in treating retroviruses (HIV).

146
Q

klebsiella is…

A

enteric gram -ve bacillus

147
Q

CSF findings in bacterial meningitis

(OP, cell type, protein, glucose)

A

OP - up

cell type - PMNs

protein - up

glucose - down

148
Q

anti-fungal that punches holes in membrane wall?

A

amphotericin B

149
Q

bacterodies is…

A

enteric gram -ve bacillus

150
Q

M tuberculosis that grows in ‘serpentine cords’ has what?

What is its function? (3)

A

Cord factor - a virulence factor associated with ability to cause disease

Cord factor = inactivates neutrophils, damages mitochondria and stimulates release of TNF-alpha

151
Q

mortalilty rate in asplenic sepsis

A

50%

152
Q

major virulence factor for strep pneumoniae

what are the other virulence factors (3)?

A

Polysaccheride capsule with >90 different types

IgA protease, pneumolysin (creates pores in cell membrane) & adhesin (adhesion to epithelial cells)

153
Q

pseudomonas, strep, haemophilus, influenza neisseria, E coli, salmonella and Klebsiella are all…

A

encapsulated organisms opsonised and removed by the spleen, so give HbS patients H influenza, S Pneumoniae and N meningitidis vaccines

154
Q

what other than treponema pallidum can give a +ve VDRL?

A

‘VDRL’ V - viral, EBV/HxV D - drugs R - rheumatic fever L - lupus, leprosy

155
Q

N gonorrhoeae Rx

A

ceftriaxone (+ doxy for possible chlamydial infection)

156
Q

proteus is…

A

enteric gram -ve bacillus

157
Q

a Gohn complex consists of what?

A

unilateral hilar adenopathy AND a Gohn focus (site of primary infection)

158
Q

intraerythrocytic pleomorphic inclusions on blood smear suggests what bug? vector for transmission? which other diseases are carried by this vector?

A
  • Babesia microti*
  • Ixodes* tick (deer tick from NE america)
  • Borellia burgdorferi* (Lyme disease) & Anaplasma spp. (human granulocytic anaplasmosis)
159
Q

Listeria is…

A

gram +ve bacillus

160
Q

sickle cell disease and osteomyelitis - what bugs?

A

salmonella and staph aureus

Remember salmonella is encapsulated with Vi(rulence) antigen that protects from opsonization

161
Q

pit versicolor Rx

A

selenium sulfide (SelSulf) + oral/topic antifungal in large quantities

162
Q

parasite association vitamin B12 deficiency

A

diphyllobothrium latum

163
Q

what bug forms biofilms on prosthetic devices/IV catheters?

A

steph epidermidis

164
Q

what bug causes lyme disease?

A

borellia burgdorferi

165
Q

alpha-haemolytic, optochin resistant strep is…

A

strep viridans type (S mutans and S mitis)

166
Q

MRSA commonly colonises what area of the body?

A

anterior nares

167
Q

bartonella is…

A

zoonotic gram -ve bacillus

168
Q

in mycoplasma pneumoniae LRTI, what is the treatment? What will not work? Why?

A

doxy, macrolides or fluroquinolone

beta-lactams

mycoplasma = pleomorphic w/o cell wall

169
Q

trichomonas vaginalis Rx

A

metronidazole for patient and partner

170
Q

which is the most important E Coli virulence factor in each of these presentations?

Neonatal meningitis

bloody/watery gastroenteritis (2 different ones)

UTI

A

NNM - K capsule, evade recognition in the blood to allow haematogenous spread

bloody gastroenteritis - verotoxin (shiga-like toxin)

watery gastroenteritis - HS/HL enterotoxin

UTI - P fimbriae allow adhesion to uroepithelium

171
Q

a budding yeast with a thick capsule, stained by mucicarmine/india ink is called what? Who does it infect? Typical presentations (2)?

A

cryptococcus neoformans

immunocompromised

cryptococcal meningioencephalitis, usually starts in lung though

172
Q

antifungal for systemic use?

A

amphotericin B

173
Q

gram +ve, catalase +ve, coagulase -ve (2)

A

staph saprophyticus and staph epidermidis

174
Q

salmonella vs shigella Abx shortens duration of symptoms

A

shigella

175
Q

Infant meningitis (3)

A

S pneumoniae, N meningitidis, HiB

176
Q

A Zeihl-Neelsen stain will be +ve for what, other than TB?

A

protozoa, e.g. cryptosporidium

177
Q

what virus causes condylomata acuminatum? common name for this condition?

where else does this virus affect?

A

HPV 1, 2, 6 and 11

anogenital warts

stratified squamous epithelium of respiratory tract = true vocal cords

178
Q

meningitis and unpasteurised dairy

A

Listeria

179
Q

two spore-forming bacteria

A

bacillus (anthrax, food poisoning) clostridium (pseudomembranous colitis, botulinum, tetanus)

180
Q

how would you get vibrio parahaemolyticus?

A

contaminated shellfish

181
Q

gamma haemolytic bacteria?

A

enterococcus

182
Q

gram +ve, coagulase +ve, catalase +ve?

A

staph aureus

183
Q

endemic typhus - what bug? How is it spread?

A

Rickettsia typhi, Rickettsia prowazekii

Fleas

184
Q

E coli is…

A

enteric gram -ve bacillus

185
Q

tetanospasmin - mechanism of action?

A

SNARE protease, inhibiting GABA/glycine inhibitor spinal neurons, disinhibited excitatory motor neurons, spastic paralysis

186
Q

salmonella, neisseria, brucella, myobacterium, listeria, yersinia, legionella are all…

A

facultative intracellular bacteria

187
Q

what does HDV need HBV co-infection for?

A

coating the HDAg internal polypeptide with HbsAg so that it can subsequently gain access to other hepatocytes

188
Q

croup - most common bug?

A

parainfluenza virus

189
Q

if not through a cat, how is toxoplasma transmitted?

A

Contaminated food

190
Q

Neisseria are cultured on what medium? what does it contain and what is the purpose of each?

A

selective, Thayer-Martin (VCN) medium.

V - vancomycin - kills gram +ve

C - colistin - kills non-Neisseria gram -ve

N - nystatin - kills fungi

191
Q

newborn meningitis bugs (birth canal)

A

GBS

E Coli

Listeria

192
Q

what is a fungus smaller than an RBC that hides within macrophages?

A

histoplasma

193
Q

what antibiotic is used for intrapartum GBS prophylaxis?

A

penicillin G (or ampicillin)

194
Q

positive Tzanck test suggests which bugs are present?

what is the Tzanck test?

A

HSV-1, HSV-2, VZV (HHV-3)

smear of opened skin vesicular fluid to look for multinucleated giant cells

195
Q

moraxella is…

A

gram -ve coccus

196
Q

what bug causes syphillis?

A

treponema pallidum

197
Q

people in close contact, low-grade fever, unremarkable physical findings, infiltrates on CXR, culture only works with cholesterol

disease name? bug? Rx (3)? haematological association?

A

Walking pneumonia

Mycoplasma pneumoniae

macrolide, tetracyline, fluoroquinolone (tetra/fluoro not for kids)

production of IgM cold agglutinin

198
Q

a Hawaiian surfer has coryza, calf pain, jaundice, conjunctivitis without exudate and photophobia. what bug?

A

leptospirosis from leptospira interrogans

199
Q

this is called? what bug? who gets it? sign of what underlying pathology?

A

ecthyma gangrenosum

pseudomonas gangrenosum

critically ill patients (& renal transplant)

pseudomonas septicaemia

200
Q

treatment of Chagas disease? (bug?)

A

nifurtimox

trypanosoma cruzi

201
Q

c diff. toxins with mechanism?

treatment for 1st line and recurrent

A

Toxin A (enterotoxic) and Toxin B (Cytotoxic). Both inactivate Rho-regulatory proteins leading to disruption of actin cytoskeleton, cell death.

Rx - metronidazole or oral vancomycin.

Recurrent Rx - fidaxomicin, faecal transplant

202
Q

the plague is what bug? How is it spread?

A

yersinia pestis rat and prairie dog fleas

203
Q

rickettsia is…

A

pleomorphic without cell wall

204
Q

Bariella is…

A

gram -ve spiral

205
Q

parasite association biliary tract disease, cholangiocarcinoma

A

clonorchis sinensis

206
Q

what receptor does RSV use to enter cells?

A

ICAM-1

207
Q

what animal gives you psittacosis?

A

parrot & other birds

chlamyophila psittaci

208
Q

blood agar with bile salts and hypertonic saline is the culture medium used to tell which gram +ve organisms apart?

A

used to tell apart the gamma-haemolytic gram +ve cocci.

  • bile salts will grow group D Strep (bovis/equinus)
  • bile salts and hypertonic saline will grow Enterococci (faecalis etc..)
209
Q

sputum gram stain showing many neutrophils with few/no organisms.

what bug?

A

Legionella

210
Q

what bug can mimic appendicitis?

A

yersinia diarrhoea with RIF pain from mesenteric adenitis/terminal ileitis

211
Q

lactobacillus is…

A

gram +ve bacillus

212
Q

helicobacter is…

A

enteric gram -ve bacillus

213
Q

this is a patchy, hypopigmented skin lesion without sensation. What is the disease called?

Caused by which bug?

A

Tuberculoid leprosy

mycobacterium leprae

214
Q

a fungus much larger than RBCs filled with its own endospores?

A

coccidioides

215
Q

why should pregnant women avoid unpasteurized cheeses and cold deli meats?

A

Listeria monocytogenes infection listeria - transplacental transmission, amnionitis, spontaneous abortion. listeria grows best 4 - 10 degC, so refrigeration makes it worse

216
Q

non-bacterial pneumonia picture.

Bronchioalverolar lavage with silver stain shows septate hyphae

A

aspergillus fumigatus

217
Q

epidemic typhus caused by what bug? How is it spread?

A

rickettsia Prowazekii

human to human by body louse

218
Q

parasite association brain cysts & seizures

A

neurocysticercosis (taenia solium)

219
Q

Rx H influenzae

options for chest and meningeal infections

A

co-amox for resp/mucosal

ceftriaxone for meningitis

220
Q

which is the most frequent anti-HIV drug to develop resistance against and what do we do to stop this?

what is the gene that is implicated in this resistance mechanism?

A

NRTIs; always give two at the same time

Pol - reverse transcriptase

221
Q

which infectious diseases present with rash on the palm and soles?

A

‘CARS’ Coxsackievirus A Rocky mountain spotted fever (rickettsia rickettsii) 2ary syphilis

222
Q

Rx of H pylori (triple therapy)

A

Antibiotics Cure Pylori

  • amoxicillin (penallergic = metro)
  • clarithromycin
  • PPI
223
Q

enterobacter is…

A

enteric gram -ve bacillus

224
Q

Giemsa stains +ve for… Certain Bugs Really Try Patients

A

Chlamydia Borrelia Rickettsia Trypanosomes (Chagas disease) Plasmodium

225
Q

parasiste association microcytic anaemia

A

ancylostoma, necator

226
Q

molluscum contageosum - what bug?

A

poxvirus

227
Q

what are 2 resistance mechanisms against vancomycin?

A
  1. mutated peptidoglycan cell wall
  2. impaired influx/increased efflux
228
Q

gram +ve haemolysis test tells between which bacteria?

A

streptococcus and enterococcus

229
Q

group A, beta-haemolytic strep is…

A

strep pyogenes

230
Q

what does flucytosine anti-fungal do?

A

inhibits nucleic acid synthesis

231
Q

which type of bug commonly causes disease in CGD?

why?

what bugs? (5)

A

catalase-positive

bugs produce hydrogen peroxide normally, so within phagolysosome will kill themselves. bugs with catalase can indefinitely survive in the phagolysosome.

Staph aureus, Burkholderia cepacia, Serratia marcescens, Nocardia, Aspergillus

232
Q

leptospira is…

A

gram -ve spiral

233
Q

what bugs are associated with a cat bite/scratch?

A
  • Pasteurella multocida* (mouse-like odour on culture)
  • Bartonella henselae* - cat scratch disaese with classic lymphadenitis
234
Q

species responsible for erythema gangrenosum?

A

pseudomonas aeruginosa

235
Q

salmonella vs shigella sensitive to gastric acid?

A

salmonella, so need to have large inoculation in order to get sick

236
Q

major complication of HHV-1

A

temporal lobe epilepsy

237
Q

on VE - thick white discharge wih inflammation

HVS - normal pH, pseudohyphae

Rx?

A

vulvovaginal candidiasis

triazole antifungals

238
Q

aspiration lobar pneumonia in alcoholics likely to be which bug?

A

Klebsiella

239
Q

which are the most common encapsulated organisms? (to watch out for in asplenism)

A

SHiN

s pneumoniae

HiB

N meningitidis

240
Q

what medication can improve the coure of measles? (not antimicrobial)
what are the 3 major complication of measles?

A

vitamin A

  1. subacute sclerosing panencephalitis (SSPE)
  2. encephalitis (1:2000)
  3. giant cell pneumonia
241
Q

treatment for sarcoptes scabiei?

A

permethrin cream

wash/dry everything in the house

treat whole family

242
Q

which leprosy has a predominant humoral response (Th2)?

A

lepromatous

243
Q

most serious consequence of neonatal HSV-2 infection?

A

meningioencephalitis

244
Q

a fungus much larger than RBC with a captain wheel formation during budding

A

paracoccidiodes

245
Q

malignant otitis externa most likely caused by what bug?

what toxins does this bug have?

A

pseudomonas aeruginosa

exotoxin A and endotoxin

246
Q

What bug is this? pathoG phrase to describe?

A

CMV

‘owl eye’ inclusion of infected cell

247
Q

treatment to prevent recurrence of genital herpes simplex flare?

A

continuous oral valacylavir daily.

248
Q

parasite association hydatid (liver) cytsts

A

echinococcus granulosus

249
Q

which gram -ve, oxidase +ve organism grows at 42 degC?

A

campylobacter

250
Q

Rx typhoid fever? distinguishing clin features?

A

ceftriaxone or fluroquinolone ‘rose spots’ on abdomen constipation then diarrhoea

251
Q

reactivation of toxoplasmosis in AIDS likely leads to what radiological finding?

A

multiple well defined ring-enhancing lesions on MRI representing abscess formation

252
Q

bruciella is…

A

zoonotic gram -ve bacillus

253
Q

spirochetes cause which 3 big diseases?

A

lyme disease syphillis leptospirosis

254
Q

what antifungal inhibits squalene epoxidase?

A

terbinafine

255
Q

obligate intracellular bacteria (3) why?

A

Rickettsia Chlamydia Coxiella .. don’t produce ATP of their own

256
Q

treatment for head lice?

A

pyrethroids/malathion/ivermecin lotion

nit combing

treat at home without taking child out of school

257
Q

EBV and CMV are also known as?

A

HHV-4 and HHV-5 respectively

258
Q

Adult meningitis bugs (3)

A

S pneumoniae, N meningitidis, HSV-2 (NB HSV-1 gives encephalitis)

259
Q

cat scratch disease caused by…

A

bartonella spp.

260
Q

Bordet-Gengou medium is used to culture…

A

Bordetella pertussis specifically

261
Q

an oocyst on acid-fast stain

A

cryptosporidium

262
Q

which HHV?

A

HHV-2

263
Q

branching filamenotous gram-positive bacteria with sulphur granules that stain dark purpule on H&E

what bug? Rx?

A

actinomyces

Penicillin

264
Q

gas gangene commonly caused by?

A

clostridium perfringes

265
Q

what cellular structure of N meningitidis is it’s main virulence factor? another important virulence factor?

A

Pilus - allows for adherence to mucosal epithelial cells, subsequent invasion of vaculature then haematogenous spread to BBB.

IgA protease - destroys mucosal antibodies allowing colonisation

266
Q

clinical test confirming Legionella infection?

A

urine legionella antigen

267
Q

most common bugs for meningitis

neonatal and adult

A

NN - GBS then E Coli (both found in birth canal) & Listeria monocytogenes

adult - Strep pneumoniae and N meningitidis

268
Q

a thorn-prick/inoculation of fungus through vegitation leading to ascending lymphangitis

A

sporothrix schenckii

269
Q

Hib commonly causes which 4 diseases?

what is the primary virulence factor of Hib?

A
  1. meningitis
  2. pneumonia
  3. epiglottitis
  4. septicaemia

VF - PRP capsule allowing evasion of mucosal immunity

270
Q

A silver stain is useful to identify which microbes?

A

Fungi Legionella H Pylori

271
Q

‘hot tub’ folliculitis is caused by what bug?

A

pseudomonas aeruginosa

272
Q

acute epiglottitis … what bug?

A

Haemophilus influenzae B

273
Q

alpha-haemolytic, optochin sensitive strep is…

A

strep pneumoniae

274
Q

other than strep, which Gram +ve bacteria is beta-haemolytic?

A

staphylococcus aureus

275
Q

sweet breath odour in the setting of increasing oxygen req’s, sputum production and fever suggests what bug?

A

pseuomonas aeruginosa

276
Q

what bug is this? 3 diseases it can cause in healthy people? neutropenia?

A
  1. vulvovaginal candidiasis
  2. cuteneous candidiasis
  3. oral thrush

neutropenia - disseminated disease that can affect any system (pneumonia, oesophagitis, right-sided endocardidis, abscesses, sepsis)

277
Q

what do the -azole antifunglas do?

A

inhibition of ergosterol synthesis, which inhibits cell wall production

278
Q

bugs responsible for bacterial pneumonia 2ary to influenza virus, in order (3)

A

Strep pneumoniae, staph aureus & H influenzae

279
Q

haemophilus is…

A

respiratory gram -ve bacillus

280
Q

contact with sheep/cow, pneumonia (culture -ve), retroorbital headache, fever >10 days duration

labs: thrombocytopenia, transaminitis

progression to fatal endocarditis

disease? bug? Rx?

A

Q fever

Coxiella burnetii

doxycycline [and hydroxychloroquine until aPL antibodies <75 GPLU]

281
Q

how does endotoxin activate macrophages? release of what? (4)

A

activation of TLR4 results in release of IL-1, IL-6 and TNF-alpha, NO

282
Q

who gets palivizumab prophylaxis?

how does it work and what does it protect against?

A

preterm infants

monoclonal Ab versus surface F protein on paramyxoviruses (childhood respiratory diseases), which usually targets these viruses to the respiratory tract

Specifically protects against RSV LRTI

283
Q

EHEC makes which toxin? mechanism of action?

A

EHEC - Shiga-like toxin, inhibition of 60S ribosomal subunit. Intestinal mucosal cell death, bleeding and diarrhoea.

284
Q

what is the broad budding infectious fungus?

A

blastomyces

285
Q

ETEC - makes what toxin? Mechanism of action?

A

heat-stable/heat-liable toxins.

HLT –> activates cAMP –> increase Cl- secretion

HST –> activate cGMP –> decrease NaCl/H2O resporbtion

286
Q

bird and bat droppings

Ohio and Mississippi river basins

A

histoplasma capsulatum

287
Q

what infections are caused by pseudomonas?

A

Hot tub foliculitis

pneumonia (CF/ventilated patients)

otitis externa (malignant)

septicaemia in neutropenia/burns

ecthyma gangrenosum

288
Q

elderly, mosquito bite in summer

meningoencephalitis, flaccid paralysis, morbilliform rash

what is the virus and what structure genome?

A

West Nile virus - ARBOvirus (arthopod-borne)

+ sense, ssRNA

289
Q

what Gram +ve most likely gives PSGN?

A

streptococcus pyogenes

usually gives impetigo first, then PSGN

290
Q

treatment for toxoplasma gondii?

A

pyrimethamine

sulfadiazine

291
Q

what is the DNA structure of HBV and how does it replicate in the cell?

A

entry of virus into cell with partially dsDNA

partially dsDNA completed upon entry to host nucleus

host RNA polymerase makes mRNA, proteins are translated

RTase makes partially dsDNA from mRNA for progeny virions

292
Q

to what bug does lecithinase belong and how is it a toxin?

A

Clostridium perfringes

breaks down phosopholipid bylayer components causing cell lysis, tissue necrosis and oedema

293
Q

what is the most common bug causing infection on foreign body implants?

what is the virulence factor important in this?

A

Staphylococcus epidermidis

formation of polysaccheride biofilm

USMLE S1 (16 decks)

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