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USMLE > Microbiology - Organisms > Flashcards

Microbiology - Organisms Flashcards

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USMLE® Step 1 flashcards
1
Q

Which bacteria do not stain well with Gram Stain?

A

(These Little Microbes May Unfortunately Lack Real Colour But Are Everywhere)

Treponema and Leptospira (too thin)
Mycobacteria (high lipid content)
Mycoplasma and Ureaplasma (no cell wall)
Legionella, Rickettsia, Chlamydia, Bartonella, Anaplasma, Ehrlichia (intracellular)

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2
Q

Which bacteria stain with Giemsa Stain?

A

(Certain Bugs Really Try my Patience)

Chlamydia, Borrelia, Rickettsia, Trypanosomes, Plasmodium

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3
Q

Which bacterium stains positive with Periodic Acid Schiff stain?

A

Stains glycogen and mucopolysaccharides.

Used to diagnose Whipple’s disease with Tropheryma whipplei.

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4
Q

What stains positive with Ziehl-Neelsen stain?

A

Mycobacteria, Nocardia, and Cryptosporidium oocytes

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5
Q

Which stains can be used to identify Cryptococcus neoformans?

A

India Ink Stain and also Mucicarmine stain.

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6
Q

What is Silver Stain used for?

A

Fungi.

Also, Legionella and Helicobacter pylori.

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7
Q

Give 3 examples of obligate aerobes:

A

(Nagging Pests Must Breathe)

Nocardia
Pseudomonas
Mycobacterium tuberculosis

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8
Q

Give four examples of obligate anaerobes:

Why are aminoglycosides ineffective against anaerobes?

A

(anaerobes Can’t Breath Fresh Air)

Clostridium
Bacteroides
Fusobacterium
Actinomyces

Aminoglycosides require oxygen to enter the cell.

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9
Q

What agar/medium should be used to culture:

H influenzae?
B pertussis?
C diphtheria?

A

Chocolate agar
Bordet-Gengou agar or Regan-Lowe medium
Telluride agar or Löffler medium

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10
Q

What agar/medium should be used to culture:

M tuberculosis?
M pneumoniae?

A 
Löwenstein-Jensen agar 
Eaton agar (requires cholesterol)
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11
Q

What agar/medium should be used to culture:

Lactose fermenting enterics?
E. coli?
Legionella?

A

MacConkey agar
Eosin-methylene blue (EBM) agar
Charcoal yeast extract agar buffered with cysteine and iron.

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12
Q

What is Thayer-Martin agar used to isolate?

How does it do this?

A

N gonorrhoea and N meningitidis.

(Very Typically Cultures Neisseria)

Selects against all others by adding Vancomycin, Trimethoprim, Colistin, Nystatin to the agar.

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13
Q

What agar/medium should be used to culture:

Fungi?

A

(Sab’s a fun guy)

Sabourard agar

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14
Q

Name 3 obligate intracellular bacteria:

A

(Really CHilly and COld? stay inside)

Rickettsia
Chlamydia
Coxiella

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15
Q

List the facultative intracellular bacteria:

A

(Some Nasty Bugs May Live FacultativeLY)

Salmonella 
Neisseria
Brucella
Mycobacterium 
Listeria
Francisella
Legionella
Yersinia pestis
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16
Q

List the common encapsulated bacteria:

A

(Please SHINE my SKiS)

Pseudomonas aeruginosa
Streptococcus pneumoniae
Haemophilia Influenzae type B
Neisseria meningitidis
Escherichia coli
Salmonella 
Klebsiella pneumoniae
group B Strep.
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17
Q

What are the Urease-positive organisms?

A

(Pee CHUNKSS)

Proteus
Cryptococcus
H pylori
Ureaplasma
Nocardia
Klebsielle
S epidermidis
S saprophyticus
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18
Q

What are the catalase-positive organisms?

A

(Cats Need PLACESS to Belch their Hairballs)

Nocardia
Pseudomonas
Listeria
Aspergillus 
Candida
E. coli
Staphylococci
Serratia
B cepacia
H pylori.
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19
Q

Which bacteria produce the following pigments?

Yellow
Gold
Blue-Green
Red

A

Actinomyces israelli has yellow “sulfur” granules
S aureus has yellow/gold crust
P aueruginosa produces a blue-green pigment
Serratia marcencens produces a red pigment.

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20
Q

What is Protein A?

Which bacteria express it?

A

It is a bacterial virulence factor which binds the FC region of IgG and prevents opsonisation and phagocytosis.

It is expressed by Staph aureus.

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21
Q

What is IgA protease?

Which bacteria express it?

A

A virulence factor enzyme that cleaves IgA allowing bacteria to adhere to and colonise mucous membranes.

Expressed by S pneumoniae, Haemophilus influenzae type B and Neisseria.

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22
Q

What is M protein?

What bacteria express it?

A

An anti-phagocytic virulence factor. The epitope is similar to self and so is does not generate a strong immune response.

Expressed by group A Streptoccoci.

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23
Q

Which 5 bacterial toxins are coded for in lysogenic phages?

A

(ABCD’S)

group A strep erythrogenic toxin
Botulinum toxin
Cholera toxin
Diphtheria toxin
Shiga toxin.
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24
Q

What is the name, mechanism of action, and manifestation of the exotoxins of:

Corynebacterium diphtheria?
Pseudomonas aeruginosa?

A
  1. Diphtheria toxin
  2. Exotoxin A

Both inhibit protein synthesis by inactivating Elongation Factor (EF-2)

Diphtheria toxin causes pseudomembranitis and bull neck
Exotoxins A causes host cell death.

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25
Q

What is the name, mechanism of action, and manifestation of the exotoxins of:

Shigella?
EHEC?

A

Shiga toxin and Shiga-like toxin both inhibit protein synthesis by inactivating the 60S ribosome.

Both cause HUS. Shiga toxin causes GI mucosal damage with dysentery.

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26
Q

What is the name, mechanism of action, and manifestation of the exotoxins of:

ETEC?
Bacillus?
Vibrio cholerae?

A

Heat-labile and heat-stable toxin for ETEC. Edema toxin for Bacillus. Cholera toxin for Cholera.

All cause increased fluid secretion by manipulating cAMP or in the case of Heat-Stable toxin, cGMP (labile in the Air, stable on the Ground).

LT and ST and Cholera cause watery diarrhoea. Edema toxin causes edematous black eschars.

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27
Q

What is the name, mechanism of action, and manifestation of the exotoxin of:

Bordetella pertussis?

A

Pertussis toxin.

Over activates cAMP and inhibits phagocytosis. Associated with whooping cough.

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28
Q

What is the name, mechanism of action, and manifestation of the exotoxins of:

Clostridium tetani?
Clostridium botulinum?

A

Tetanospasmin and Botulinum.

Both are pro teases that cleave the receptor required for NT release, Tetanospasmin prevents release of inhibitory GABA (spastic paralysis). Botulinum prevents release of excitatory Ach (flaccid paralysis).

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29
Q

What is the name, mechanism of action, and manifestation of the exotoxins of:

Clostridium perfringins?
Streptococcus pyogenes?

A

Alpha toxin and Steptolysin O. Both lyse cell membranes.

Alpha toxin has a lecithinase which causes myonecrosis and haemolytic. Streptolysin O is a protein that lyses RBCs.

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30
Q

What is the name, mechanism of action, and manifestation of the SUPERANTIGENS of:

Staphylococcus aureus?
Streptococcus pyogenes?

A

TSST-1 and Exotoxin-A.

Both cross link MHC II and TCR to stimulate multiple colonies of Lymphocytes, causing massive cytokine release.

TSST-1 is more impressive. Exotoxin-A is associated with Scarlett fever.

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31
Q

What are the antibiotics tests and sensitive/resistant species in the Staphylococcus lineage?

A

(NO StRESs on the Staph. retreat)

NOvobiocin - saprophyticus is Resistant. Epidermidis is Sensitive.

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32
Q

What are the antibiotics tests and sensitive/resistant species in the Streptococcus lineage?

A

(OVRPS and B-BRAS)

Optochin - Viridians is Resistant. Pneumoniae is Sensitive.

Bacitracin - group B strep are Resistant. group A strep are Sensitive.

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33
Q

What are the alpha-haemolytic bacteria?

Which antibiotics is used to distinguish between certain species?

A

Partial reduction of haemoglobin causes greenish or brownish colour with a clearing on blood agar.

Streptococcus pneumoniae (cat- and Optochin S)
Viridians streptococcus (cat- and Optochin R)
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34
Q

What are the beta-haemolytic bacteria?

Which antibiotics is used to distinguish between certain species?

A

Complete lysis of Red Blood Cells with clearing on blood agar.

Staphylococcus aureus (cat+ coag+)
Streptococcus pyogenes (cat- Bacitracin S)
Streptococcus agalacticae (cat- Bacitracin R)
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35
Q

(______________) is a gram +, lancet-shaped diplococci associated with rusty sputum and a virulent capsule.

It is the most common cause of?

A

Meningitis
Otitis media in children
Bacterial pneumonia
Sinusitis

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36
Q

What are the Viridians group Streptococci?

Where do they live and what distinguishes them from Strep pneumoniae?

A

S. mutants, S. mitis (dental caries) and S. sanguinis (SBE)

Live in the mouth as they are not afraid “of-the-chin” (Optochin resistant, which distinguishes them from S. pneumoniae).

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37
Q

Scarlett fever is caused by and manifests how?

A

Streptococcus pyogenes (group A strep)

Blanching, sandpaper like body rash, strawberry tongue, circumoral pallor in the setting of GAS pharyngitis.

Mediated by Erthrogenic toxin.

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38
Q

Bovis in the blood means…

A

Cancer in the colon

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39
Q

What is Woolsorter’s disease?

How does it manifest and what causes it?

A

Pulmonary (cf cutaneous) anthrax. Manifests as flu-like illness that rapidly progresses to pulmonary haemorrhage and mediastinitis and shock.

Caused by gram +, spore forming Bacillus anthracis. The only bacterium with a polypeptide capsule!

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40
Q

What causes “reheated rice syndrome”?

A

Bacillus cereus.

Nausea and vomiting within one hour. Diarrhoea and cramping within 8-15 hours.

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41
Q

What are the four Ds of Botulism?

A

Dysarthria
Diplopia
Dyspnoea
Dysphagia

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42
Q

What are the two toxins of C. difficile?

A

Toxin A - enterotoxin which binds to brush border and alters fluid secretion

Toxin B - cytotoxin which disrupts cytoskeleton

Both cause diarrhoea and pseudomembranous colitis.

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43
Q

Lab diagnosis of Corynebacterium diphtheria?

A

Gram positive rods with metachromic (blue and red) granules

Positive Elek test for toxin

Black colonies of cysteine-tellurite agar.

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44
Q

Classification, acquisition, microscopic appearance, pathological conditions and treatment of Listeria monocytogenes?

A

Gram positive facultative intracellular rod.

Unpasteurised dairy and cold deli meats.

Forms “rocket tails” and tumble around in broth (VF to avoid antibody)

Amnionitis, sepsis, abortion. Treat with Ampicillin.

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45
Q

Describe the staining, pathogenic conditions, and treatment of the (2) branching, filamentous bacteria:

A

Nocardia (aerobic, weakly acid fast, mimics TB)

Actinomyces (anaerobic, not acid fast, causes oral/facial abscesses associated with dental carries. Yellow “sulfer granules”. Also PID)

Treatment is a SNAP: Sulfonamides for Nocardi, Actinomyces treated with Penicillin.

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46
Q

What are the two forms of Leprosy (Hansen disease)?

What is the treatment?

A
  1. Lepromatous - diffuse skin involvement with leonine facies, characterised by low cell-mediated immunity with a humoral Th2 response. Can be Lethal.
  2. Tuberculoid - limited to a few hypoesthetic, hairless skin plaques. High cell-mediated immunity with largely Th1 response.

Treatment with Dapsone and Rifampicin. Add Clozamine for lepromatous leprosy.

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47
Q

Name four examples of lactose fermenting bacteria:

How do they grow on MacConkey’s and EBM agar?

A

(maconKEES agar)

Klebsiella. E coli. Enterobacter. Serratia.

All form pink colonies of MacConkey’s. Lactose fermenters grow as purple/black colonies on EBM. E. coli is blue/green on EBM.

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48
Q

What is the distinguishing feature in lab analysis between meningococcus and gonococcus?

A

Meningococci ferment both maltose and glucose.

Gonococci only ferment glucose.

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49
Q

What would you use for Meningococcus prophylaxis in close contacts of affected patients?

A

Rifampicin, Ceftriaxone, or Ciprofloxacin.

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50
Q

Why does Haemophilus influenzae require chocolate agar to grow?

What can it be grown with instead?

A

Chocolate agar provides factors V and X (hematin).

Can also be grown with Staph aureus which hemolyses RBS providing factor V.

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51
Q

What does HaEMOPhilus cause?

What is the treatment?

A

Epiglottis - Augmentin
Meningitis - Ceftriaxone
Otitis media - Augmentin
Pharyngitis - Augmentin

Rifampicin for close contacts.

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52
Q

What are the two clinical manifestations of Legionella pneumophilia?

How can you test for them?

What is the mode of transmission?

A

Legionnaire’s disease - severe pneumonia, often unilateral and lobar. Fever, GI and CNS symptoms. Common in smokers and COPD.

Pontiac fever - mild flu-like syndrome.

Can test for Legionella antigen in urine. Often see hyponatraemia.

Transmitted via aerosol eg AC or water tanks.

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53
Q

What are the microscopic features of Pseudomonas aeruginosa?

What are its (4) virulence factors?

A

Aerobic, motile, gram - rod. Non-lactose fermenting. Oxidase +.

  1. Pyocynin (generates ROS)
  2. Endotoxin (fever, shock)
  3. Exotoxin A (host cell death)
  4. Phopholipase C (degrades cell membranes)
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54
Q

What are the available treatments for Pseudomonas aeruginosa?

A

(CAMPFIRE)

Carbapenams
Aminoglycosides
Monobactams
Polymyxins (polymyxin B or Colistin)
Fluoroquinolones
thIRd and fourth generation cephalosporins
Extended-spectrum penicillins (piperacillin, ticarcillin)

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55
Q

What is Haemolytic Uraemic Syndrome?

A

A triad of anaemia, thrombocytopenia, and acute renal failure due to microthrombi forming on damaged endothelium. Characterised by mechanical haemolysis (so schistocytes are seen on peripheral film).

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56
Q

What are the predominant virulence factors seen on pathogenic E. coli?

A

Fimbriae (P-pili) - for adhesion in pyelonephritis and cystitis

K capsule - pneumonia and neonatal meningitis

LPS endotoxins

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57
Q

What are the four most important strains of E. coli?

A

EIEC - Invasive dysentery
ETEC - Traveller’s diarrhoea
EPEC - Paediatric strain diarrhoea
EHEC - Enterohaemorrhagic. Causes HUS.

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58
Q

Why are the 5 A’s of KlebsiellA?

A 
Aspiration pneumonia
Abscesses in lung and liver
Alcoholics
di-A-betics
"curr-A-nt jelly" sputum
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59
Q

Both Salmonella and Shigella are gram negative rods, non-lactose fermenters, oxidase negative, and can invade the GI tract via M cells of Peyer patches.

What are 5 key differences?

A

Shigella’s only reservoir is humans (like S. typhoid)
Shigella is cell to cell spread only (both S. spp via blood too)
Shigella requires only a small inoculum
Shigella have no flagella
Antibiotics reduce duration of symptoms in Shigella

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60
Q

What is Typhoid fever?

What is it caused by?

A

An illness characterised by rose spots on the abdomen, constipation, abdominal pain, and fever.

Caused by Salmonella typhi.

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61
Q

What are the three clinically important species of Spirochetes?

Which one can be seen with light microscopy?

A

Borrelia (can be visualised with Giemsa stain)
Leptospira
Treponema.

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62
Q

What two disease are caused by Leptospira interrogans?

A

Leptospirosis - flu-like symptoms, calf myalgia, jaundice, photophobia with conjunctival suffusion. Prevalent in the tropics and in surfers.

Weil disease - severe form of above with jaundice and azotemia and renal dysfunction, haemorrhage, and anaemia.

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63
Q

Which disease is caused by Borrelia burgdorferi?

How is it transmitted?

Which animal is crucial in the vector’s life cycle?

A

Lyme disease.

Transmitted by the Ixodes deer.

The natural reservoir is the mouse.

64
Q

What are the three stages of Lyme disease?

A

(a key Lyme pie to the FACE)

  1. Early localisation. Erythema mirgans and flu like symptoms
  2. Early disseminated. Secondary lesions, carditis, AV block, facial nerve palsy, migratory myalgia/transient arthralgia.
  3. Late disseminated. Encephalopathies, chronic arthritis.
65
Q

Which bacteria causes syphilis?

How and when can you test for it?

A

Treponema pallidum.

Patients with primary syphilis are VDRL+ 80%
Patients with secondary and tertiary syphilis are VDRL+
Confirm with FTA-ABS and PCR.

66
Q

Describe the manifestations of primary, secondary, and tertiary syphilis:

A

Painless chancres in primary.

Systemic symptoms in secondary; maculopapular rash, condylomata lata, lymphadenopathy, patchy hair loss.

Tertiary syphilis manifests with gummas, aortitis, neurosyphilis, Argyll-Robertson pupil, ataxia.

67
Q

How does congenital syphilis present?

How can it be prevented?

A

Facial abnormalities (rhagades, snuffles, saddle nose), notched teeth, short maxilla, and CN VIII deafness.

Prevent by treating mother early in pregnancy (transmission after first trimester).

68
Q

What causes false positives on VDRL testing?

A

Viral infections (EBV, hepatitis)
Drugs
Rheumatic fever
Lupus and Leprosy

69
Q

What are the histological features and clinical presentation of Gardnerella vaginalis infection?

How is it diagnosed?

How is it treated?

A

Gardnerella vaginalis is pleomorphic gram negative rod involved in bacterial vaginosis. “Clue” cells are seen on histology: vaginal epithelial cells covered with Gardnerella.

Diagnosed with Amine whiff tests (mix with 10% KOH)

Infection typically manifests as a grey vaginal discharge with a fishy odour which is non-painful.

70
Q

The “palms and soles” distribution of rash is seen in which illnesses?

A

(drive CARS with palms and soles)

Coxsackievirus A
Rocky Mountain spotted fever
Secondary syphilis

71
Q

How do you group the Rickettsial and vector-borne illnesses?

A

Rash common - RMSF and Typhus

Rash rare - Ehrlichiosis, Anaplasmosis, Q fever.

72
Q

What are the causes and typical dermatological findings of Rocky Mountain Spotted Fever and Typhus?

A

RMSF - caused by R. rickettsii. Rash typically starts at wrists and ankles, then spreads to trunk, palms, and soles.

Typhus - caused by R. typhi (fleas) and R. prowazeckii (human body louse). Rash starts centrally and spreads out sparing palms and soles.

73
Q

What are the two forms Chlamydia takes?

A

Elementary body is the “enfector” and enters the cell using endocytosis.

Reticulate body replicates in the cell by fission and reorganises into elementary bodies.

74
Q

Which bacteria is common to both dog-bites and cat-bites?

What are its microscopic and culture features?

A

Pasteurella multocida.

Gram negative coccobacilli, the culture has a mousy odour.

75
Q

How do you subcategorise clinical mycology?

A

Systemic mycoses
Cutaneous mycoses
Opportunistic mycoses

76
Q

What are the systemic mycoses?

How are they treated?

A

Histoplasmosis
Blastomycosis
Coccidioidomycosis
Paracoccidioidomycosis

Fluconazole or Itraconazole for local infection.
Amphotericin B for systemic infection.

77
Q

Described the endemic location, pathological features, and unique signs/symptoms of:

Blastomycosis

A

Eastern and Central US.

Blasto buds broadly (same size as RBC).

Inflammatory lung disease and can mimic SCC cutaneously. Granulomatous nodules.

78
Q

Described the endemic location, pathological features, and unique signs/symptoms of:

Coccidioidomycosis

A

Southwestern US and California (desert bumps/rheumatism)

Spherules filled with endospores of Coccidioides. Much larger than RBC.

Disseminates to bone and skin to form Desert Bumps or Desert Rheumatism. Can cause meningitis.

79
Q

Described the endemic location, pathological features, and unique signs/symptoms of:

Paracoccidioidomycosis

A

Latin America.

Budding yeast forms “captain’s wheel”.

Similar to coccidioidomycosis.

80
Q

List the types of Tinea:

What is seen on blue fungal stain?

A

Capitis, corporis, cruris, predis, unguium, versicolour.

Branching septate hyphae are visible on KOH preparation with blue fungal stain.

81
Q

What causes pityriasis versicolour?

What is the classical appearance on microscopy?

What is the treatment?

A

Pityrosporum malassezia.

“Spaghetti and meatballs” appearance.

Selenium sulphide and topical/oral antifungals.

82
Q

What are the clinically important opportunistic fungal infections?

A 
Candida albicans
Aspergillosis fumigatus
Cryptococcus neoformans
Mucor and rhizopus species
Pneumocystis jiroveci
Sporothrix schenkii
83
Q

What is a dimorphic fungus?

List the clinically important ones:

What is the exception?

A

“Mould in the Cold, Yeast in the Beast”

“Body Heat Probably (Changes) Shape”:
Blastomycosis, Histoplasma, Paracoccidioides, (Coccidioides), Sporothrix.

Candida is the exception as it changes to mould with heat!

84
Q

Aspergillus branches at?

Mucor and Rhizopus branch at?

A

Acute angles 45 degrees

Wide angles.

85
Q

Which fungus causes “soap bubble” lesions?

Which fungus causes disease predominantly in neutropenic and DKA patients?

Which fungus appears as disc shaped yeast on methanamime silver stain?

A

Cryptococcus neoformans
Mucor and Rhizopus spp.
Pneumocystis jirovecii.

86
Q

Brief description of Sporothrix schenkii?

A

“A Rose Gardener who smokes a cigar and pot”

Opportunistic dimorphic fungal infection, often introduced by rose thorns. Causes local pustules or ulcers with ascending lymphangitis.

Microscopy appearances of cigar-shaped budding yeast with rosettes of conidia.

87
Q

How do you subcategorise clinical mycology?

A

Systemic mycoses
Cutaneous mycoses
Opportunistic mycoses

88
Q

What are the systemic mycoses?

How are they treated?

A

Histoplasmosis
Blastomycosis
Coccidioidomycosis
Paracoccidioidomycosis

Fluconazole or Itraconazole for local infection.
Amphotericin B for systemic infection.

89
Q

Described the endemic location, pathological features, and unique signs/symptoms of:

Histoplasmosis

A

Mississippi and Ohio river valleys.

Histo hides in macrophages filled with histoplasma (smaller than RBC)

Palatal or tongue ulcers and splenomegaly. Spelunker’s lung.

90
Q

Described the endemic location, pathological features, and unique signs/symptoms of:

Blastomycosis

A

Eastern and Central US.

Blasto buds broadly (same size as RBC).

Inflammatory lung disease and can mimic SCC cutaneously. Granulomatous nodules.

91
Q

Described the endemic location, pathological features, and unique signs/symptoms of:

Coccidioidomycosis

A

Southwestern US and California (desert bumps/rheumatism)

Spherules filled with endospores of Coccidioides. Much larger than RBC.

Disseminates to bone and skin to form Desert Bumps or Desert Rheumatism. Can cause meningitis.

92
Q

Described the endemic location, pathological features, and unique signs/symptoms of:

Paracoccidioidomycosis

A

Latin America.

Budding yeast forms “captain’s wheel”.

Similar to coccidioidomycosis.

93
Q

List the types of Tinea:

What is seen on blue fungal stain?

A

Capitis, corporis, cruris, predis, unguium, versicolour.

Branching septate hyphae are visible on KOH preparation with blue fungal stain.

94
Q

What causes pityriasis versicolour?

What is the classical appearance on microscopy?

What is the treatment?

A

Pityrosporum malassezia.

“Spaghetti and meatballs” appearance.

Selenium sulphide and topical/oral antifungals.

95
Q

What are the clinical important opportunistic fungal infections?

A 
Candida albicans
Aspergillosis fumigatus
Cryptococcus neoformans
Mucor and rhizopus species
Pneumocystis jiroveci
Sporothrix schenkii
96
Q

What is a dimorphic fungus?

List the clinically important ones:

What is the exception?

A

“Mould in the Cold, Yeast in the Beast”

“Body Heat Probably (Changes) Shape”:
Blastomycosis, Histoplasma, Paracoccidioides, (Coccidioides), Sporothrix.

Candida is the exception as it changes to mould with heat!

97
Q

Aspergillus branches at?

Mucor and Rhizopus branch at?

A

Acute angles 45 degrees

Wide angles.

98
Q

Which fungus causes “soap bubble” lesions?

Which fungus causes disease predominantly in neutropenic and DKA patients?

Which fungus appears as disc shaped yeast on methanamime silver stain?

A

Cryptococcus neoformans
Mucor and Rhizopus spp.
Pneumocystis jirovecii.

99
Q

Brief description of Sporothrix schenkii?

A

“A Rose Gardener who smokes a cigar and pot”

Opportunistic dimorphic fungal infection, often introduced by rose thorns. Causes local pustules or ulcers with ascending lymphangitis.

Microscopy appearances of cigar-shaped budding yeast with rosettes of conidia.

100
Q

Describe the disease, transmission, diagnosis, and treatment of:

Giardia lamblia

A

Giardiasis.

Fatty, foul smelling, flatulent diarrhoea.

Cysts in water.

Metronidazole.

101
Q

Describe the disease, transmission, diagnosis, and treatment of:

Entamoeba histolytica

A

Amebiasis. Dysentery, liver abscesses (anchovy paste), RUQ pain.

Cysts in water.

Serology or Entamoeba Eats Erythrocytes appearance.

Metronidazole.

102
Q

Describe the disease, transmission, diagnosis, and treatment of:

Cryptosporidium.

A

Severe diarrhoea in AIDS. Mild disease in immunocompetent.

Oocytes in water.

Oocytes seen on AF stain.

Nitazoxanide.

103
Q

How do you subcategorise the clinically important Protozoan infections?

A

Gastrointestinal infections.
CNS infections.
Haematological infections.
Others.

104
Q

Describe the disease, transmission, diagnosis, and treatment of:

Toxoplasma gondii

A

Congenital toxo = triad of chorioretinitis, hydrocephalus, intracranial calcifications. Reactivation in AIDS (ring enhancing lesions).

Transmitted as cysts in meat or oocytes in cat faeces.

Diagnosed on serology and biopsy.

Treated with sulfadiazine and pyrimethamine.

105
Q

Describe the disease, transmission, diagnosis, and treatment of:

Naegleria fowleri

A

Rapidly fatal meningitis.

Freshwater lakes containing Naegleria.

Amoebas in spinal fluid.

Amphotericin B maybe…

106
Q

Describe the disease, transmission, diagnosis, and treatment of:

Trypanosoma brucei

A

African sleeping sickness. Sleepy and recurring fever with lymphadenopathy.

Tsetse fly, a painful bite.

Trypomastigote in blood smear.

Suramin and melarsoprol. (Sur am sleepy - melanin for sleep)

107
Q

Describe the disease, transmission, diagnosis, and treatment of:

Babesia

A

Babesiosis. Fever and haemolytic anaemia. North eastern US.

Haematological protozoan infection transmitted by the same Ixodes tick as Lyme disease.

Blood smear shows ring form or Maltese cross.

Atovaquone and azithromycin.

108
Q

Describe the disease cycle of Plasmodium:

  • vivax/ovale
  • falciparum
  • malariae
A

Fever, headache, anaemia, splenomegaly.

  • 48 hour cycle so tertian pattern
  • severe, irregular fever patterns
  • 72 hour cycle so quartan pattern
109
Q

Which species of mosquito transmits malaria?

A

Anopheles.

110
Q

What are the findings on blood smear with malarial infection?

A
  1. Trophozoite ring form within RBC
  2. Schizont containing merozoites
  3. Red granules (Schuffner stippling) seen with vivid/ovale.
111
Q

What is the treatment for malaria?

A

Chloroquine, if resistant use Mefloquine or Atovaquone. IV quinidine for life-threatening disease.

112
Q

Describe the disease, transmission, diagnosis, and treatment of:

Trypanosoma cruzi

(“Cruzing in my Benz with a Fur coat on)

A

Chagas disease. Dilated cardiomyopathy with apical atrophy, mega-colon, mega-oesophagus. Unilateral periorbital swelling in acute phase (Romana sign).

Reduviid bug faeces.

Typomastigote in blood smear.

Benznidazole or nifurtimoz

113
Q

What are the routes of Nematode infection?

A
  1. Ingested
  2. Cutaneous
  3. Bites
114
Q

List the ingested Nematodes:

A

“you’ll get sick if you EATT these”

Enterobius
Ascaris
Toxocara
Trichinella

115
Q

List the cutaneous Nematodes:

A

“these get into your feet from the SANd”

Strongyloides
Ancylostoma
Necator

116
Q

List the Nematodes transmitted by bite:

A

“lay LOW to avoid getting bitten”

Loa loa
Onchocerca volvulus
Wuchereria bancrofti

117
Q

Treatment for most Nematodes?

A

Bendazoles

Ivermectin for rIVER blindness

118
Q

Treatment for Tapeworms and Flukes?

A

Praziquantel or Albendazole

119
Q

What are the live attenuated viral vaccines?

A

“Music and lYRICSS are best enjoyed Live”

MMR, Yellow fever, Rotavirus, Influenza (intranasal), Chickenpox, Smallpox, Sabin polio virus.

120
Q

What are the killed viral vaccines?

A

“RIP Always”

Rabies, Influenza (injected), Salk Polio, Hepatitis A.

121
Q

All DNA viruses are dsDNA except for?

A

Parvovirus (single stranded DNA)

122
Q

All RNA viruses are ssRNA except for?

A

Reoviridiae (which is dsRNA)

123
Q

List the single stranded RNA viruses

A

“I went to a retro toga party, where I drank flavoured corona and ate hippie California pickles”

Retrovirus
Togavirus
Flavivirus
Coronavirus
Hepevirus
Calicivirus
Picornavirus
124
Q

The naked nucleic acids of which types of virus are infectious? Explain.

A

The purified naked acids if most dsDNA and positive strand RNA viruses are infectious. Naked nucleic acids of negative strand DNA and RNA viruses require polymerases contained in the complete virion.

125
Q

Where do DNA viruses replicate?

Any exceptions?

A

The nucleus. Except Pox virus; “box is out of the box” (in the cytoplasm).

126
Q

Where do RNA viruses replicate?

Any exceptions?

A

All RNA viruses replicate in the cytoplasm.

Except influenza and retroviruses (which replicate in the nucleus).

127
Q

List the non-enveloped or “naked” viruses

These can be either RNA or DNA…

A

“Give PAPP smears and CPR to a naked Hippie”

PAPP are DNA, CPR H are RNA

Papillomavirus
Adenovirus
Parvovirus
Polyomavirus
Calicivirus
Picornavirus
Reovirus
Hepevirus.
128
Q

Where do “naked” viruses acquire their envelopes?

Is there an exception?

A

Generally, from the plasma membrane upon exiting the cell.

Herpesviruses acquire their envelopes from the nuclear membrane.

129
Q

List the clinically important DNA viruses.

A

“HHAPPPPy viruses”

Hepadna, Herpes, Adeno, Pox, Parvo, Papilloma, Polymyoma

130
Q

Which DNA viruses do NOT have linear genomes?

A

Papilloma and Polyoma (circular and supercoiled) and hepadna (circular and incomplete).

131
Q

What shape are the DNA viruses?

Is there an exception?

A

All DNA viruses are icosahedral.

Except pox (complex).

132
Q

Which skin condition/infection is caused by poxvirus?

A

Molluscum contagiosa; flesh-coloured papule with central umbilication, usually painless.

133
Q

What clinical conditions does Adenovirus cause?

A

Febrile pharyngitis
Acute hemorrhagic cystitis
Penumonia
Conjunctivitis (pink-eye)

134
Q

What is the medical importance of papillomavirus?

A

Papillomavirus causes HPV condyloma accuminatum (serotypes 1, 2, 6, 11), CIN, and cervical cancer (serotypes 16, 18).

135
Q

What is the medical importance of Polyomavirus?

A

JC virus and BK virus.

JC causes progressive multifocal encephalopathy
BK affects transplant patients, targets the kidney.

136
Q

What is the medical importance of Parvovirus?

A

Parvovirus B19 causes slapped-cheek in immunocompetent hosts but can precipitate aplastic crisis in patients with SSD. Hydrops fettles in utero.

137
Q

What is the morphology of the Herpesviridiae?

A

Enveloped, DS, and linear viruses.

138
Q

Which herpesviridiae causes:

Sporadic encephalitis? (most common cause of this)
Gingivostomatitis etc?
Herpes Genitalis?
Chickenpox, Encephalitis, Pneumonia?

A

HSV-1
HSV-1
HSV-2
Varicella Zoster or HHV 3

139
Q

Which herpesviridiae causes:

Mononucleosis?
Roseola infantum?
Kaposi Sarcoma?

A

HHV-4 (EBV) or HHV-5 (CMV)
HHV-6 and HHV-7
HHV-8

140
Q

Which human herpesviridiae has a characteristic owl eye on histology?

A

HHV-5 or CMV.

141
Q

What is a Tzanck test?

A

“Tzanck heavens I do not have Herpes”

A smear of of an opened skin vesicle to detect multinucleate giant cells commonly seen in HSV-1, HSV-2, and VZV infection.

142
Q

Receptors used by viruses:

CMV?
EBV?
HIV?
Parvovirus B19?
Rabies?
Rhinovirus?
A 
CMV - Integrins (heparin sulphate)
EBV - CD21 on B cells
HIV - CXCR4 and CXCR5 on CD4+ cells
B19 - P antigen on RBCs
Rabies - Nicotinic AChR
Rhinovirus - ICAM-1
143
Q

List the clinically important Picornaviruses and their diseases:

A

PERCH on a Pic(ornavirus)

Poliovirus - Polio
Echovirus - Aseptic meningitis
Rhinovirus - "Common cold"
Coxsackievirus - Aseptic meningitis, HF&M disease, myocarditis, pericarditis
HAV - Acute viral hepatitis.
144
Q

What are the clinically important Paramyxovirises

A

PaRaMyxovirus

Parainfluenza - Croup
RSV - Bronchiolitis in babies (Rx Ribavirin)
Mumps and Measles.

145
Q

List the clinically important negative stranded viruses:

How do they create AA progeny?

A

Must transcribe negative to positive strand so virion brings its own RNA dependent RNA polymerase

“Always Bring Polymerase Or Fail Replication”

Arenaviruses
Bunyaviruses
Paramyxoviruses
Orthomyxoviruses
Filoviruses
Rhabdoviruses
146
Q

Name the segmented (RNA) viruses

A

Segemented viruses are a BOAR

Bunyaviruses
Orthomyxoviruses
Arenaviruses
Reoviruses

147
Q

“Councilman bodies” are seen in?

A

Yellow Fever and other causes of hepatic necrosis.

They are eosinophilic globules surrounded by other hepatocytes.

148
Q

Describe the antigens of the Influenza and Parainfluenza viruses. What do they do?

A
  1. Haemagglutinin - Binds silica acid and promotes viral entry)
  2. Neuraminidase - Promotes progeny virion release
149
Q

Describe the virus class and classic symptoms of:

Rubella virus

A

A togavirus.

Fever, (post-auricular) lymphadenopathy, arthralgia, and a fine confluent rash that starts on the face and spreads centrifugally.

150
Q

Describe the diseases and pathogenic protein of:

The Paramyxoviruses

A

Paramyxoviruses cause disease in children.

Croup, measles, mumps, RSV, and human metapneumovirus.

All contain surface F (fusion) protein, which causes respiratory cells to fuse into multinucleate cells.

151
Q

What is the MAB for paramyxovirus?

A

Palivizumab for Paramyxovirus Prophylaxis in Premies

152
Q

What are the 4 “C”s of Measles?

A

Cough
Coryza
Conjunctivitis
Koplick Spots.

153
Q

What kind of virus is Rabies?

Where does it bind?

What is the disease progression?

A

Rabies is a Rhabdovirus

It binds Ach receptors and travels up dyne motors.

Starts with fever, malaise, then agitation, photophobia, hydrophobia, hyper salivation, then paralysis, coma, and then death.

154
Q

What type of Virus is HIV?

A

HIV is a positive single stranded RNA retrovirus, which is part of there Lentivirus family.

It is positive ssRNA

155
Q

What are the 3 structural genes of HIV?

What do they code for?

A

env - gp160 becomes gp140 and gp21
gag - p24 and p17 (capsid and matrix proteins)
pol - reverse transcriptase, aspartate protease, and integrase.

156
Q

How is HIV diagnosed?

A

ELISA as initial test (high FP)

Results confirmed with Western Blot Assay (looks for antiBODIES to HIV proteins)

Viral loads for prognosis

157
Q

How is AIDS diagnosed?

A

Based on CD4+ count:

Less than or equal to 200 (normal = 500-1500)
or
HIV positive with AIDS defining illness
or 
CD4+ count less than 14%

USMLE (14 decks)

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