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Rapid Review Step 1 > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Thayer Martin VCN medium

A

Selective for Niesseria (e.g N.Gonorreha Gram-ive diplococci)
Medium contains vancomycin, Colisistin, Nystatin, Trimethoprim
which kills all others except Nisseria.

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2
Q

Group-A Strep

A

AKA Strep Pyogenes
M-protien (virulence factor)
resist phagocytosis (molecular mimicry)
has structural homology to Tropomyosin & Myosin reacts to epitopes on mysoin causing Rheumatic carditis

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3
Q

Main Causes of UTI

A

E-coli, Klebsiella, Proteus, Enterobacteria, Staph Saprophyticus

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4
Q

Congenital Syphillis

A

Tryponema Palladium (Spirochete)
Atypical Delivery
Abcess like foci of necrosis around umbilical vessels
Growth Restriction
Late symptoms(can be prevented by penicillin) are saddle nose & notched teeth
VDRL+, Rapid Reagin test

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5
Q

Organisms causing risk of ectopic Pregnancy

A

Nisseria Gonorrhea , Chlamydia trachomatis
cause PID and tubular scaring which increases the risk of ectopic pregnancy.

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6
Q

Clostridium Tetani

A

Causes tetanus
metalloprotease exotoxin tetanospasmin inhibits neurotransmitters Glycine & GABA
Muscle spasms, hyperreflexia, lock jaws

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7
Q

Scabies

A

Sarcoptes scabiei mite infestation Spread by direct person-to-person contact
Extremely pruritic, small, erythematous papules
Distribution: interdigital web spaces, flexor wrists, extensor elbows, axillae, feet, umbilicus & genitalia
Burrows (thin serpiginous lines) may not be visible but pathognomonic if present

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8
Q

H.Pylori

A

Gastritis, Ulcers, PUD
Also assosiated with MALT Lymphoma

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9
Q

Herpes

A

doble strand DNA virus (ds DNA)

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10
Q

HPV

A

ds DNA virus

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11
Q

Chlamydia

A

obligate intracellular bacteria; causes PID, cervicitis (yellow pus), or conjunctivitis (Neonatal blindness)

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12
Q

Niesseria Gonorrhea

A

gram-negative diplococcus;
presents with mucopurulent discharge; can be present with palmar pustule, arthritis/ joint pain, urethral discomfort

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13
Q

Hemophilus ducreyi

A

Gram Negative Rods
Causes CHANCROID (painful with a necrotic center)

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14
Q

CMV

A

Enveloped ds DNA virus
Causes congenital blinding
Can also cause pneumonitis & CMV retinitis
Immunocompromised patient at high risk (i.e transplant patients, HIV etc)

Histology : Enlarged cells with intranuclear and intracytoplasmic inclusions (OWLs EYE NUCLEUS)
there is often surrounding halo.

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15
Q

West Nile Virus

A

West Nile fever:
fever, headache, rash (maculopapular/morbilliform)
Neuroinvasive:
meningitis, encephalitis, acute asymmetric flaccid paralysis
Parkinsonian symptoms (eg, rigidity, bradykinesia, tremor)

West Nile virus is a single-strand flavivirus transmitted by mosquitoes, most commonly in the summer. Most infections are asymptomatic or may present with a flu-like illness (West Nile fever), often with a maculopapular or morbilliform rash. Neuroinvasive disease manifests as meningitis, encephalitis, or asymmetric flaccid paralysis; patients may have parkinsonian features (eg, tremor

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16
Q

Bordetella Pertussis

A

Gram –ive coccobacilli
Whooping cough
May be assosiated with vomitting and nausea

Tracheal toxin : destroy ciliated epithelial cells leads to loss of airway clearence

Pertussis/ AB toxin: activates adenylate cyclase leading to alteration in signalling inhibit phagocytosis and cause lymphocytosis.

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17
Q

Toxoplasma Gondii

A

Causes toxoplasmosis, seen in HIV patients
Multiple ring enhanced lesions in temporal lobe.

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18
Q

Clostridiodes difficile

A

Part of normal gut flora
Increase growth due to killing of other GI flora due to antibiotic use
Has Toxin A, Toxin B stimulate inflamatory reaction and disrupt the actin cytoskeletal structure resulting in pseudomembranous colitis characterized by:

Crampy abdominal pain
Watery Diarrhea
Leukocytosis

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19
Q

Norovirus

A

Single stranded RNA genome
MCC of viral gastroenteritis in developed countries
Acute onset resolves in 2-3 days
Vomitting
Watery Diarrhea (No blood or Mucus)
Fecal oral spread
Outbreaks in crowded settings

20
Q

MacConkey Agar

A

Selective for gram negative rods

Gram –ive Bacilli (Rods) =
lactose fermenting (Colonies turn pink) & Non lactose fermenting

Lactose fermenting:
Slow- Citrobacter , Serratia

Fast- Inodole +ive = E.coli (ability to convert tryptophan to inodole)
Inodole –ive = Klebsiella , Enterobacter

Non-Lactose fermenting:
Oxidase +ive = Pseudomonas
Oxidase –ive =
H2S producing : Salmonella, Proteus
Non H2S producing : Shigella , Yersinia

21
Q

ETEC

A
  • Enterotoxigenic E. coli causes traveler’s diarrhea.
  • Will present as brown/green diarrhea in person who’s gone to
    Mexico or Middle East classically.
  • Heat-labile toxin ADP ribosylates adenylyl cyclase ↑ ­ cAMP.
  • Heat-stable toxin ADP ribosylates guanylyl cyclase ↑ ­ cGMP.
22
Q

EHEC

A
  • Enterohemorrhagic E. coli causes bloody diarrhea 1-3 days after consumption of beef.
  • Produces shiga-like toxin, which can cause hemolytic uremic syndrome
    (HUS; triad of renal dysfunction, schistocytosis, thrombocytopenia).
23
Q

Shigella

A
  • Bloody diarrhea 1-3 days after consumption of beef.
  • Also can cause HUS via shiga toxin.
  • Requires very few organisms to cause infection.
  • Main virulence is via its ability to invade, not the toxin itself.
  • Both shiga toxin of Shigella and shiga-like toxin of EHEC inhibit protein synthesis by cleaving the eukaryotic 60S ribosomal subunit
24
Q

Yersinia enterocolitica

A
  • Causes bloody diarrhea + either appendicitis-like (i.e., RLQ) pain or arthritis.
  • The RLQ pain is from mesenteric adenitis or terminal ileitis.
  • Toxin has same MOA as ETEC heat-stabile toxin (i.e., ­ cGMP).
25
Q

Campylobacter jejuni

A
  • Bloody diarrhea 1-3 days after consumption of poultry.
  • Can cause Guillain-Barre syndrome (ascending paralysis + ¯ tendon reflexes + albuminocytologic dissociation in the CSF –> Tx with IVIG + plasmapheresis).
  • Grows best at high temperatures (42 degrees).
26
Q

Bacillus cereus

A
  • Watery diarrhea and/or vomiting in patient who’s consumed reheated or fried rice. The process of heating/re-heating causes germination of spores.
  • Can also cause eye infections.
27
Q

Clostridium perfringens

A
  • Watery/secretory diarrhea following consumption of poultry.
  • Causes gas gangrene (CO2 gas) due to production of alpha-toxin/phospholipase; presents as black skin / crepitus.
  • Can also cause emphysematous cholecystitis (air in gall bladder wall).
28
Q

Clostridium difficile

A
  • Diarrhea (pseudomembranous colitis) ~7-10 days after commencing oral antibiotics.
  • Diagnose with stool AB toxin test.
  • Treat with oral vancomycin.
29
Q

Trichinella spiralis

A
  • Ingested by eating pork/bear meat.
    Causes triad of fever, periorbital edema, and myalgias. (Trichinosis)
30
Q

Taenia solium

A
  • Pork tapeworm.
    Causes cysticercosis (muscle pain/cysts) + neurocysticercosis
    (“Swiss cheese” appearance of brain or soap bubbles in ventricles).
31
Q

Haemophilus
Influenzae

A
  • Causes Epiglottitis
  • Inflamed Epiglottitis;
  • Thumbprint sign on Xray
  • 2-3 Years old & unvaccinated children
  • Capsule (Polyribitol Phosphate) inhibits Phagocytosis;
  • IgA Proteases
  • Gram (-) Rods grow on Chocolate Agar
  • Tx: Ceftriaxone
32
Q

Parainfluenza
(paramyxoviridae)

A
  • Causes: Croup, Laryngotracheitis, Laryngotracheobronchitis
  • Fever, sharp barking cough, inspiratory hoarse phonation, steeple sign on AP Xray seen on Croup.
  • Seen in Infants
  • Tx: Rivabarin
33
Q

Respiratory Syncytial Virus RSV
(paramyxoviridae)

A
  • Causes Bronchitis, Bronchiolitis
  • Wheezing
  • Infants or Child <5 Years old
34
Q

Mycoplasma pneumoniae

A
  • Causes Bronchitis, Bronchiolitis.
  • Seen in Child >5 year old.
  • Release of 02 radicals causes necrosis of epithelium.
  • Slow Growth on Eaton Medium.
  • Cold agglutinins.
35
Q

Streptococcus pneumoniae

A
  • Gram (+) diplococcus, alpha
    hemolytic, catalase (-), lysed by bile, inhibited by optochin.
  • Causes Typical Lobar pneumonia.
  • Rust colored sputum;
  • Lobar pneumonia or less commonly, bronchopneumonia
  • Seen in Adults and Alcoholics.
  • Anti-phagocytic capsule.
  • IgA protease.
  • Tx : Macrolides + Quinolones
36
Q

Staphylococcus Aureus

A
  • Gram (+), Catalase (+) cocci in chains.
  • Causes Typical Lobar pneumonia.
  • Nosocomial/respiratory Salmon colored sputum.
  • A protein binds to Fc of IgG to inhibit opsonization and phagocytosis.
  • Tx : Beta-lactams, Carbapenems, Vancomycin.
37
Q

Klebsiella pneumonia

A
  • Encapsulated Gram (-) rod, Oxidase (-),
    Lactose fermenting Facultative anaerobe.
  • Causes aspiration assossiated typical pneumonia.
  • Chronic, lung disease, alcoholism or diabetes.
  • Currant jelly sputum.
  • Capsule protects against phagocytosis.
  • Tx : Ceftriaxone +/- Aminoglycoside
    Carbapenem for ESBL-strains
38
Q

Anaerobes, mixed infection
(Bacteroides, Fusobacterium, Peptococcus)

A
  • Aspiration of vomit, leads to enzyme damage, leads to anaerobic foci.
  • Foul Smelling Sputum.
  • Tx : Empiric Antibiotic Therapy
    (Amoxicillin-Clavulanate, Gentamicin)
39
Q

Pseudomonas aeruginosa

A
  • Gram (-) rod, Oxidase (+), Glue green pigments.
  • Seen in Neutropenic patients, burn patients, Chronic Granulomatous Disease, Cystic Fibrosis.
  • Biofilm, Exotoxin A.
  • Tx : Azithromycin, Third-Generation Cephalosporin.
40
Q

Yersinia pestis

A
  • Gram (-) rod, Coagulase (+) with a safety pin appearance
    (bipolar staining).
  • Cause of bubonic and pulmonic plagues (this
    one, characterized by pulmonary septic emboli),
  • Fever + Buboes.
  • Flea bite (vector); Wild rodents are carriers (prairie dogs).
  • Tx : Aminoglycosides.
41
Q

Influenza A and B
(Orthomyxoviridae)

A
  • Fever, Headache, Malaise, Myalgia and Cough.
  • ”Flu” season.
  • Antigenic drift (Influenza A and B).
  • Antigenic shift (Influenza A).

Tx :
- Oseltamivir, Zanamivir
(Neuraminidase inhibitors)
- Killed vaccine

42
Q

Francisella tularensis

A
  • Gram (-) Aerobe, Cysteine (+)
  • Inhalation of aerosolized blood from butchering or skinning rabbits.
43
Q

Chlamydophila psittaci

A
  • Gram (-) Obligate intracellular.
  • Atypical pneumonia.
  • Exposure to birds and/or parrots.
  • Association with hepatitis.

Tx : Tetracycline, Erythromycin.

44
Q

Pneumocystis jirovecii

A
  • MCC cause of pneumonia in AIDS.
  • Interstitial plasma cell pneumonia.
  • Methamine silver cysts.

Tx : TMX-SMX.

45
Q

Streptococcus pyogenes

A
  • Gram (+), Catalase (-) coccus;
  • Beta-hemolytic, Bacitracin sensitive.
  • Inflamed tonsils/pharynx, abscesses; cervical lymphadenopathy, fever, stomach upset, sandpaper rash.
  • Exotoxins A-C (superantigens).
  • Tx : Penicillin.

Rapid Review Step 1 (7 decks)

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