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USMLE Step 1 > Microbiology > Flashcards

Microbiology Flashcards

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USMLE® Step 1 flashcards
1
Q

Bugs that do not Gram stain well

A

“These Little Microbes May Unfortunately Lack Real Colour But Are Everywhere”

  • Treponema, Leptospira (too thin)
  • Mycobacteria (cell wall high lipid)
  • Mycoplasma, ureaplasma (no cell wall)
  • Legionella, Rickettsia, Chlamydia, Bartonella, Anaplasma, Ehrlichia (intracellular)
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2
Q

Bugs that stain with Giemsa stain

A

“Certain Bugs Really Try my Patience”

  • Chlamydia
  • Borrelia
  • Rickettsia
  • Trypanosomes
  • Plasmodium
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3
Q

Which stain stains glycogen and mucopolysaccharides?

Used to diagnose which disease?

A

“PaSs the sugar”
Periodic acid-Schiff stain
- Whipple disease: Tropheryma whipplei

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4
Q

Ziehl-Neelsen stain used for:

A

Acid-fast bacilli (also auramine-rhodamine stain)
- Mycobacteria, Nocardia
Protozoa
- Cryptosporidium

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5
Q

Indian ink stain used for? Alternative?

A

Cryptococcus neoformans

Also mucicarmine - stains thick polysaccharide capsule red

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6
Q

Silver stain used for:

A
  • Fungi (coccidioides, PJP)
  • Legionella
  • H pylori
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7
Q

Which fluorescent Ab stain used to stain syphilis?

A

FTA-ABS

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8
Q

2 properties of growth agars and eg of each

A
  • Selective media: favours growth of one org eg Thayer Martin agar selects for Neisseria
  • Indicator (differential) media: yields colour change in resp to metabolism of certain org eg MacConkey agar = pH indicator (detects E. coli - lactose fermenter –> lactic acid)
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9
Q

Chocolate agar cultures:

A

H influenza

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10
Q

Thayer-Martin agar contains what and cultures which organism:

A

Cultures N gonorrhoeae and N meningitidis
“Very Typically Cultures Neisseria”
- Vancomycin inhibits Gram +ve org
- Trimethoprim, colistin inhibit Gram -ve besides Neisseria
- Nystatin inhibits fungi

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11
Q

B pertussis is cultured on which media

A

Bordet-Gengou (bordet for Bordetella)

Regan-Lowe

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12
Q

C diphteriae cultured on which media

A

Tellurite agar

Loffler medium

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13
Q

Lowenstein-Jensen agar cultures which organism

A

M Tb

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14
Q

Eaton agar used for which organism

A

M pneumoniae

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15
Q

Lactose-fermenting enterics cultured with

A

MacConkey agar

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16
Q

E coli cultured with

A

Eosin-methylene blue (EMB) agar

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17
Q

Sabouraud agar used for:

A

Fungi

“Sab’s a fun guy!”

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18
Q

Examples of aerobes

A

“Nagging Pests Must Breathe”
Nocardia
Pseudomonas
MycoBacterium TB

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19
Q

Examples of anaerobes

A

Anaerobes “Can’t Breathe Fresh Air”

  • Clostridium
  • Bacteriodes
  • Fusobacterium
  • Actinomyces
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20
Q

Examples of obligate intracellular bugs

A

stay inside when it’s “Really CHilly and COld”

  • Rickettsia
  • Chlamydia
  • Coxiella
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21
Q

Examples of Facultative intracellular bugs

A

“Some Nasty Bugs May Live FacultativeLY”

  • Salmonella
  • Neisseria
  • Brucella
  • Mycobacterium
  • Listeria
  • Francisella
  • Legionella
  • Yersinia pestis
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22
Q

Examples of encapsulated bacteria

A

“Please SHINE my SKiS”

  • Pseudomonas
  • Strep pneumo
  • H influenza type B
  • Neisseria meningitidis
  • E coli
  • Salmonella
  • Klebsiella
  • group B Strep
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23
Q

List the urease positive orgs

A

“Pee CHUNKSS” - predispose to struvite stones

  • proteus
  • cryptococcus
  • H pylori
  • ureaplasma
  • nocardia
  • klebsiella
  • S epidermidis
  • S saprophyticus
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24
Q

Eg of catalase positive bugs and clinical significance

A

“Cats Need PLACESS to Belch their Hairballs”

  • Nocardia
  • Pseudomonas
  • Listeria
  • Aspergillus
  • Candida
  • E coli
  • Staphylococci
  • Serratia
  • B cepacia
  • H pylori

Cx recurrent infections in Chronic Granulomatous Disease (NAPDH oxidase deficiency)

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25
Q

5 A’s of Klebsiella

A 
Aspiration pneumonia
Abscesses
Alcoholics
di-A-betics
currAnt jelly sputum
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26
Q

4 D’s of botulism

A

Diplopia
Dysarthria
Dysphagia
Dyspnoea

27
Q

Pseudomonas associated with:

A

PSEUDOMONAS

  • P-neumona, pyocyanin
  • S-epsis
  • Ecthyma gangrenosum
  • UTI
  • Diabetes, drugs (IV)
  • Osteomyelitis
  • Mucoid polysaccharide capsule
  • Otitis externa
  • Nosocomial infections
  • exotoxin A
  • Skin infection (hot tub folliculitis)
28
Q

Treatments for pseudomonas

A

CAMPFIRE

  • Carbapenems
  • Aminoglycosides
  • Monobactams
  • Polymyxins (polymyxin B, colistin)
  • Fluoroquinolones
  • thIRD and 4th gen cephalosporins
  • Extended spectrum penicillins (piperacillin, ticarcillin)
29
Q

VDRL false positives

A

VDRL

  • Viral infections (EBV, hepatitis)
  • Drugs
  • Rheumatic fever
  • Lupus and leprosy
30
Q

Rash on palms and soles suggestive of:

A

“drive CARS with palms and soles”

  • Coxsackievirus A
  • Rocky Mountain Spotted Fever
  • Syphilis (secondary)
31
Q

Rare rashes transmitted via ticks

A

“MEGA berry”

  • Monocytes with morulae - Ehrlichiosis
  • Granulocyte with morulae - Anaplasmosis
32
Q

Which nematode causes obstructive symptoms (and where)?

A

Giant roundworm (ascaris lumbricoides)

  • ileocecal valve
  • biliary obstruct
  • intestitinal perforation
33
Q

Which nematode causes anaemia?

What’s the cutaneous condition called?

A

Hookworms (ancylostoma duodenale, Necator americanus)
- sucks blood from intestinal wall

Cutaneous larva migrans

34
Q

Which nematode mimics peptic ulcer symptoms?

A

Threadworm (strongyloides stercoralis)

- vomiting, diarrhoea, epigastric pain

35
Q

Which nematode causes muscle inflammation

A

Trichinella spiralis - Trichinosis

  • fever, vomiting, nausea, periorbital oedema, myalgia
  • from undercooked meat (pork)
36
Q

Treatment of head/pubic lice

A

Pyrethroids, malathion, ivermectin lotion

37
Q

Micro-organisms that cause rashes in hands and feet

A 
Syphilis
Rickettsia rickettii (Rocky Mountain spotted fever)
Coxsackie A (Hand Foot and Mouth disease)
38
Q

Clinical manifestations of Coxsackie B

A

Dilated cardiomyopathy
Bornholm’s disease/pleurodynia (Devil’s Grip)
- usually unilateral lower pleuritic chest pain

39
Q

How to inactivate Hep A virus (in water)

A

Chlorinated
Bleached
UV irradiated
Boiled 85 deg for 1min

40
Q

What/where are calicivirus (norovirus) commonly transmitted?

A

Cruises
Day cares/schools
Shellfish

41
Q

Features of congenital rubella

A

ID, microcephaly, congenital cataracts, blindness, deafness, PDA, pulmonary stenosis, jaundice, purpuric blueberry muffin rash, radiolucent bone lesions

42
Q

HIV infections in CD4 <500

A 
Candida - oral thrush
EBV - oral hairy leukoplakia
Bartonella henselae - bacillary angiomatosis
HHV-8 - Kaposi sarcoma
HPV - squamous cell CA (anus/cervix)
43
Q

HIV infections in CD4 <200

A

Histoplasma capsulatum - histoplasmosis
HIV dementia
JC virus reactivation - Progressive multifocal leukoencephalopathy
Pneumocystis jirovecii - PCP

44
Q

HIV infections in CD4 <100

A 
Aspergillosis
Oesophageal candidiasis
CMV - retinitis, oesophagitis, colitis, pneumonitis, encephalitis
Cryptococcal meningitis
Cryptosporidium spp - chronic diarrhoea
EBV - B cell lymphoma
Mycobacterium avium comples
Toxoplasmosis - brain abscess
45
Q

List the segmented viruses

A 
BOAR
Bunyavirus
Orthomyxovirus
Arenavirus
Reovirus
46
Q

Features of Reye’s syndrome

A 
Rapidly progressing encephalitis
Fever
Vomiting
CNS sx - personality changes, confusion, seizures
LOC
Fatty liver
47
Q

Common cx of pneumonia in neonates (<4wks)

A

E coli

Group B strep

48
Q

Common cx of pneumonia in children (4wk - 18yo)

A 
Viruses (RSV)
Mycoplasma
Chlamydia trachomatis (infants - 3yr)
Chlamydophila pneumoniae (school-aged)
Strep pneumo

“Runts May Cough Chunky Sputum”

49
Q

Common cx of pneumonia in young adults (18-40yr)

A

Mycoplasma
C pneumoniae
S pneumoniae
Viruses (eg influenza)

50
Q

Common cx of pneumonia in older adults (40-65yo)

A 
S pneumoniae
H influenza
Anaerobes
Viruses
Mycoplasma
51
Q

Common cx of pneumonia in elderly

A 
S pneumonia
Influenza virus
Anaerobes
H influenza
Gram neg rods
52
Q

Common cx of meningitis in newborns (0-6mo)

A

Group B strep
E coli
Listeria

53
Q

Common cx of meningitis in children (6mo - 6yr)

A

S pneumoniae
N meningitides
H influenzae type B
Enteroviruses

54
Q

Common cx of meningitis in 6-60yos

A

S pneumoniae
N meningitides
HSV
Enteroviruses

55
Q

Common cx of meningitis in >60yos

A

S pneumonia
Gram neg rods
Listeria

56
Q

What is Bornholm disease

A

“devil’s grip” - epidemic pleurodynia. Severe, unilateral pleuritic pain in lower chest

57
Q

Classic triad of congenital toxoplasmosis

A

Chorioretinitis
Hydrocephalus (with seizures)
Intracranial calcifications

58
Q

Findings in Dengue fever + mode of transmission

A
  • Acute febrile illness with headache, retro-orbital pain, joint and muscle pain
  • Haemorrhage (petechiae, purpura, epistaxis, melena)
  • thrombocytopenia
  • leukopenia
  • hemoconcentration

-Aedes mosquito

59
Q

4 D’s of botulism

A

Diplopia
Dysarthria
Dysphagia
Dyspnoea

60
Q

Outline some NB components of cell walls for Gram +/-, mycobacteria and fungi

A
  • N-acetylmuramic acid and N-acetylglucosamine: peptidoglycan layer in both G+ and G-
  • Teichoic acid: G+ bacteria only
  • LPS: Gram -ve bacteria
  • mycolic acid: acid fast bacilli (mycobaceria and nocardia)
  • Fungi: ergosterol
61
Q

Genes of which bacterial toxins are encoded in the lysogenic phage?

A

ABCD’S

  • group A strep erythrogenic toxin
  • Botulinum toxin
  • Cholera toxin
  • Diphtheria toxin
  • Shiga toxin
62
Q

Features of disseminated gonococcal infection

A 
Triad of:
- Polyarthralgia
- Tenosynovitis
- Dermatitis (painless pustules at extremities)
Also: purulent arthritis
Diagnosed on Thayer-Martin media
63
Q

Features of invasive non-typhoidal salmonella

A

Osteomyelitis
Mycotic aneurysm
Endocarditis
Visceral abscesses

64
Q

Triad of hemolytic uremic syndrome

A

Renal insufficiency
Thrombocytopenia
Microangiopathic hemolytic anemia

USMLE Step 1 (11 decks)

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