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USMLE Step 1 flashcards > Microbiology > Flashcards

Microbiology Flashcards

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USMLE® Step 1 flashcards
1
Q

Which are the microorganisms produce intraerythrocytic infections? and which are their characteristics?

A
  • babesia—- intraerythrocytic rings, vector— tick—coinfection with borrelia (lyme disease)
  • plasmodium spp
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2
Q

Which streptoccocal components produce scalet fever?

A

erythrogenic toxin

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3
Q

which is the mechanism through influenzae virus achieve antigenic shift? and how explain it?

A

Reassortment: enchange genetic material, it is possible because of segmented genome.

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4
Q

which is the cause and main characteristics of the renal struvite stones?

A
  • Urease positive microorganisms: Proteus, Cryptococcus, H pylori, Ureaplasma,
    Nocardia, Klebsiella, S epidermidis, S saprophyticus
  • Calculus fill entire renal pelvis
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5
Q

Congenital toxoplasmosis triad

A
  • Chorioretinitis
  • Hydrocephalus
  • Intracranial calcifications
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6
Q

Relate these conditions with some parasites

  • biliary tract disease and cholangiocarcinoma
  • liver hidatid cyst
  • microcytic anemia
  • myalgias
  • Vit B12 deficiency
A
  • Clonorchis sinensis
  • Echinococcys granulosus
  • Necator- ancylostoma
  • Trichinella spiralis
  • Diphyllobothrium latum
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7
Q

8 families of naked virus

A

Papilomavirus, adenovirus, parvovirus, polyomavirus, calicivirus, picornavirus, reovirus and hepevirus.

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8
Q

7 families of DNA virus and exceptions

A
  1. Herpesvirus, Hepadnavirus, Adenovirus, Polyomavirus, Poxvirus, Parvovirus, Papillomavirus
  2. All are dsDNA except parvovirus
    - All replicate in nucleus except Porxvirus (carries DNA -dependent RNA polymerase)
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9
Q

which are the main C. difficile pathogenic factor?

A

alpha toxin (phospholipase C) is a lecithinase—-disrupts membranes, damaging RBCs, platelets, WBCs, endothelial cells— massive hemolysis, tissue destruction, hepatic toxicity.

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10
Q

Mechanisms of bacterial resistance to aminoglucosides

A
  • poor drug penetration through bacterial membrane
  • failure to drug binding to 30s ribosomal subunit due to mutation
  • Drug destruction by bacterial enzymes
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11
Q

ADHD treatment

A

Methylphenidate and anphetamines: Increase releasing of norepinephrine and dopamine from vesicular storage sites.
Blocking NE and dopame reuptake

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12
Q

antibiotics against anaerobic bacterias

A
  • piperacilin-tazobactam
  • carbapenems
  • clindamycin
  • metronidazole
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13
Q

Protein A

A

Part of peptidoglycan layer—virulence factor of S. aureus —- binds to fc portion of IgG— inhibiting complement activation and phagocytosis.

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14
Q

Enterotoxigenic E. coli

A

heat level toxin (LT)
activate cAMP —- increased Cl in gut and H2O efflux
“Cholera like toxin”
travelers diarrhea

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15
Q
  • Candida

- Blastomyces

A
  • Pseudohyphae with blastoconideas, budding yeast

- yeast with distinctive broad beased budding

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16
Q
  • coccidiomicoses
  • Cryptococco
  • Hystoplasma
A
  • spherules with endospores
  • capsule (india ink)
  • small oval yeast within macrophages
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17
Q

Legionella pneumophila

A

Silver stains
charcoat yeast agar suplemmented cysteine and iron
contaminates natural water
pneumoniae, diarrhea, hyponatremia

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18
Q

Influenza virus vaccine

A

Inactivated version of vaccine—- inducing neutralizing abs against hemagglutinin antigen— prevents virus entering the cell via endocytosis

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19
Q

Germ tubes

A

true hyphae—- specific for Candida albicans

20
Q

Primaquine

A

Mus be added to treatment regimen against P. vivax and ovale—- to erradicate hipnozoites

21
Q

Haemophilus

A

requires X factor (hematin) V factor (NAD+) to support growth.
Will grow around B hemolytic S. aureus because secrete factor V

22
Q

Streptococo

alpha, beta y gamma hemolytic

A
  • alpha: viridans (optohin resistant and bilis insoluble). pneumoniae (optochin sensitive and bilis soluble)
  • beta: pyogenes (pyr positive and bacitracin sensitive), agalactiae (pyr negative and bacitracin resistance)
  • gamma: enterococcus (pyr positive, grow in 6.5% NaCl), bovis (pyr negative and not grow in 6.5% NaCl)
23
Q

coccidiodes immitis

A

dismorphic fungus
microscopic examination: thick wall spherules with endospores
immunocompetent localized infection: lungs
immunocompromised: systemic infection

24
Q

Streptococo pyogenes

A

Beta hemolytic
Coagulase- catalase negative
PyR positive
Bacitracin sensitive

25
Q

Q fever

A

Coxiella burnetti
animal waste
Acute: non specific fever- fatigue- severe debilitating headaches retroorbital, photofobia, pneumonia, thrombocytopenia, increase liver enzymes
Chronic: fatal if is untreated, endocarditis if the patient has valvular disease

26
Q

Clostridium difficile enterocolitis

A 
toxin A (enterotoxic) and B (cytotoxic)
Toxin B more virulent: inactvated rho regulatory protein---------involved in signal transduction and actin cytoskeletal structure maintenance --- disrupction of intercelleular tight junction.
Damaged cytoskeletal integrity
27
Q

Which is the main cause of septic shock and septicemia of meningitis by N. meningitidis?

A

Lipoolygosacharide (LOS)

Endotoxin

28
Q

Dynein and kinesin

A

In herpes zoster dynein: retrograde transport (skin to nerve)
Kinesin: anterograde transport (nerve to skin)

29
Q

West nile virus

A

fever, rash and neurologic manifestations
most common in erderly patients
encefalitis and flaccid paralysis
RNA virus– flavivirus, transmitted by mosquito (culex)

30
Q

Saline microscopy

A

best diagnstostic test to identify trichomonas

31
Q

Why is the difficult to develop vit c vaccine?

A

has 6 o more genotypes—-the virion encodes RNA dependent RNA polymerase without 3´-5´ proofreading exonuclease activity: results in many errors during replication. — hypervariable genomic regions—-such sequences coding envelope glycoproteins

32
Q

Acute hepatitis B

A

Systemic, skin, joint symptoms, hepatomegaly and elevated transaminases (> 10 times over normal limit).
May develop a serum sickness like syndrome: joint pain, lymphadenopathy and prurituc urticarial vasculitis rash
could or not be icteric
Elevated Pt: poor prognosis

33
Q

three main mechanisms for genetic transfer between bacteria

A
  • transformation: bacteria take up naked DNA for the environment.
  • Conjugation: DNA is passed from one bacterium to another by direct cell-cell interaction
  • transduction: bacteriophage - mediated transfer of genetic information
34
Q

Difference between reassortment and phenotypic mixing

A

phenotypic mixing: the progeny of new strain remain unchanged
Ressortment: any genomic change is always present in subsequent progeny

35
Q

Hepatitis D and B relation

A

Hepatitis D antigen isconsidered replication defective as it must be coaled by exteral coat hep B surface antigen————-to PENETRATE hepatocyte

36
Q

How could minimized recurrent HSV-2 recurrent lesions?

A

daily valacyclovir, acyclovir or famciclovir

minimized replication

37
Q

Novobiocin test

A

applying in coagulase negative microorganisms,
sensitive: Staphylococcus epidermidis
Resistant: S. saprophyticus

38
Q

The most mediator of sepsis?

A

TNF alpha

39
Q

Ecthyma gngrenosum

A

P. aeruginosa
Exotoxin A (protein synthesis inhibitor)
Elastase(degrades elastin— blood vessel destruction)
Phospholipase C (degrades cellular membrane)
Pyocianin (generates ROS)
*** perivascular bacterial invasion of arteries and veins—- dermis and subcutaneous tissue.

40
Q

Absolute neutrophil count

A

0.6* Number of leucocyte

If it is less than 500 /mm3 = neutropenia

41
Q

Roseola infantum

A

HHV 6

3-5 days with fever ——- then a blanching maculopapular generalized rash

42
Q

Ghon complex

A

initial infection of M. tuberculosis

lower lung lobe lesion (fibrotic focus) + ipsilateral hilar adenopathy

43
Q

Common intracellular pathogens

A

Chlamydia, francicella, laegionella, listeria, mycobacterium, N. gonorrhea, nocardia, ricketssia, salmonella and yersinia
** Cell mediated immunes response: INF gamma, TNF alpha, and IL-2

44
Q

outer membrane is characteristic of…

A

gram negative

contain: LPS and LOS

45
Q

Bacillary angiomatosis

A

produced muy bartonella henselae in immunocompromised patients (catscratch). Vascular lesions in skin as papules, and in viscera

USMLE Step 1 flashcards (10 decks)

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