Microbiology - Virology (2) Flashcards

Question 1

Q

Influenza viruses

Properties
Vaccine

Answer

A

Properties
- Orthomyxoviruses.
- Enveloped, (-) ssRNA viruses with 8-segment genome.
- Contain hemagglutinin (promotes viral entry) and neuraminidase (promotes progeny virion release) antigens.
- Patients at risk for fatal bacterial superinfection.
- Rapid genetic changes.
Vaccine
- Reformulated vaccine (“the flu shot”) containing the viral strains most likely to appear during the flu season.
- Killed viral vaccine is most frequently used.
- Live, attenuated (temperature-sensitive mutant) vaccine that replicates in the nose but not in the lung, administered intranasally.

Question 2

Q

Genetic shift / antigenic shifts vs. genetic drift

Genetic shift / antigenic shifts
Genetic drift

Answer

A

Genetic shift / antigenic shifts
- Causes pandemics.
- Reassortment of viral genome
  - Segments undergo high-frequency recombination, such as when human flu A virus recombines with swine flu A virus.
Genetic drift
- Causes epidemics.
- Minor (antigenic drift) changes based on random mutation.
Sudden shift is more deadly than gradual drift.

Question 3

Q

Rubella virus

Properties
Causes…

Answer

A

Properties
- A togavirus.
Causes…
- Causes rubella, once known as German (3-day) measles.
  - Fever, postauricular and other lymphadenopathy, arthralgias, and fine rash [A].
- Causes mild disease in children but serious congenital disease (a ToRCHeS infection).
  - Congenital rubella findings include “blueberry muffin” appearance, indicative of extramedullary hematopoiesis [B].

Question 4

Q

Paramyxoviruses

Causes…
Properties
Prevention

Answer

A

Causes…
- Paramyxoviruses cause disease in children.
- They include those that cause parainfluenza (croup: seal-like barking cough), mumps, and measles as well as RSV, which causes respiratory tract infection (bronchiolitis, pneumonia) in infants.
Properties
- All contain surface F (fusion) protein, which causes respiratory epithelial cells to fuse and form multinucleated cells.
Prevention
- Palivizumab (monoclonal antibody against F protein) prevents pneumonia caused by RSV infection in premature infants.

Question 5

Q

Measles virus

Properties
Causes…
Prevention

Answer

A

Properties
- A paramyxovirus that causes measles.
Causes…
- Koplik spots [A] and descending maculopapular rash [B] are characteristic.
- SSPE (subacute sclerosing panencephalitis, occurring years later), encephalitis (1:2000), and giant cell pneumonia (rarely, in immunosuppressed) are possible sequelae.
- 3 C’s of measles:
  - Cough
  - Coryza
  - Conjunctivitis
Prevention
- Vitamin A used to prevent severe exfoliative dermatitis in malnourished children.

Question 6

Q

Mumps virus

Properties
Causes…

Answer

A

Properties
- A paramyxovirus.
Causes…
- Symptoms: Parotitis [A], Orchitis (inflammation of testes), and aseptic Meningitis.
  - Mumps makes your parotid glands and testes as big as POM-poms.
- Can cause sterility (especially after puberty).

Question 7

Q

Rabies virus

Properties
Causes…
Treatment

Answer

A

Properties
- Bullet-shaped virus [A].
- Negri bodies [B] commonly found in Purkinje cells of cerebellum and in hippocampal neurons.
- More commonly from bat, raccoon, and skunk bites than from dog bites in the United States.
Causes…
- Rabies has long incubation period (weeks to months) before symptom onset.
- Progression of disease: fever, malaise –> agitation, photophobia, hydrophobia –> paralysis, coma –> death.
- Travels to the CNS by migrating in a retrograde fashion up nerve axons.
Treatment
- Postexposure treatment is wound cleansing and vaccination ± rabies immune globulin.

Question 8

Q

HAV

Virus
Transmission
Carrier?
Incubation
HCC risk?
Notes

Answer

A

Virus
- RNA picornavirus
Transmission
- Fecal-oral
Carrier?
- No
Incubation
- Short (weeks)
HCC risk?
- No
Notes
- Asymptomatic (usually), Acute, Alone (no carriers)
- HAV and HEV are fecal-oral
  - The vowels hit your bowels.
  - Naked viruses do not rely on an envelope so they are not destroyed by the gut.

Question 9

Q

HBV

Virus
Transmission
Carrier?
Incubation
HCC risk?
Notes

Answer

A

Virus
- DNA hepadnavirus
Transmission
- Parenteral, sexual, maternalfetal
Carrier?
- Yes
Incubation
- Long (months)
HCC risk?
- Yes: integrates into host genome, acts as oncogene
Notes
- In HBV, the DNA polymerase has both DNA- and RNA-dependent activities.
- Upon entry into the nucleus, the polymerase functions to complete the partial dsDNA.
- The host RNA polymerase transcribes mRNA from viral DNA to make viral proteins.
- The DNA polymerase then reverse transcribes viral RNA to DNA, which helps form new viral particles

Question 10

Q

HCV

Virus
Transmission
Carrier?
Incubation
HCC risk?
Notes

Answer

A

Virus
- RNA flavivirus
Transmission
- Primarily blood (IVDU, posttransfusion)
Carrier?
- Yes
Incubation
- Long
HCC risk?
- Yes: from chronic inflammation
Notes
- Chronic, Cirrhosis, Carcinoma, Carrier

Question 11

Q

HDV

Virus
Transmission
Carrier?
Incubation
HCC risk?
Notes

Answer

A

Virus
- RNA delta virus
Transmission
- Parenteral, sexual, maternalfetal
Carrier?
- Yes
Incubation
- Superinfection (HDV after HBV)—short
- Co-infection (HDV with HBV)—long
HCC risk?
- Yes
Notes
- Defective virus Dependent on HBV
- Superinfection –> decreased prognosis

Question 12

Q

HEV

Virus
Transmission
Carrier?
Incubation
HCC risk?
Notes

Answer

A

Virus
- RNA hepevirus
Transmission
- Fecal-oral, especially with waterborne epidemics
Carrier?
- No
Incubation
- Short
HCC risk?
- No
Notes
- High mortality in pregnant women
- Enteric, Expectant mothers, Epidemic
- HAV and HEV are fecal-oral:
  - The vowels hit your bowels.
  - Naked viruses do not rely on an envelope so they are not destroyed by the gut.

Question 13

Q

Signs and symptoms of all hepatitis viruses

Answer

A

Episodes of fever
Jaundice
Increased ALT and AST.

Question 14

Q

Hepatitis serologic markers (166)

Anti-HAV (IgM)
Anti-HAV (IgG)
HBsAg
Anti-HBs
HBcAg
Anti-HBc
HBeAg
Anti-HBe

Answer

A

Anti-HAV (IgM)
- IgM antibody to HAV
- Best test to detect active hepatitis A.
Anti-HAV (IgG)
- IgG antibody indicates prior HAV infection and/or prior vaccination
- Protects against reinfection.
HBsAg
- Antigen found on surface of HBV
- Indicates hepatitis B infection.
Anti-HBs
- Antibody to HBsAg
- Indicates immunity to hepatitis B.
HBcAg
- Antigen associated with core of HBV.
Anti-HBc
- Antibody to HBcAg
  - IgM = acute/recent infection
  - IgG = prior exposure or chronic infection.
- Positive during window period.
HBeAg
- A second, different antigenic determinant in the HBV core.
- Indicates active viral replication and therefore high transmissibility.
Anti-HBe
- Antibody to HBeAg
- Indicates low transmissibility.

Question 15

Q

Hepatitis serologic markers (166)

For each
- HBsAg?
- Anti-HBs?
- HBeAg?
- Anti-HBe?
- Anti-HBc IgM/IgG?
Acute HBV
Window
Chronic HBV (high infectivity)
Chronic HBV (low infectivity)
Recovery
Immunized

Answer

A

Acute HBV
- HBsAg (+)
- HBeAg (+)
- Anti-HBc IgM
Window
- Anti-HBe (+)
- Anti-HBc IgM
Chronic HBV (high infectivity)
- HBsAg (+)
- HBeAg (+)
- Anti-HBc IgG
Chronic HBV (low infectivity)
- HBsAg (+)
- Anti-HBe (+)
- Anti-HBc IgG
Recovery
- Anti-HBs (+)
- Anti-HBe (+)
- Anti-HBc IgG
Immunized
- Anti-HBs (+)

Question 16

Q

HIV

Genome
The 3 structural genes (protein coded for)
Mechanism
Homozygous vs. heterozygous

Answer

A

Genome
- Diploid genome (2 molecules of RNA).
The 3 structural genes (protein coded for)
- env (gp120 and gp41)
  - Formed from cleavage of gp160 to form envelope glycoproteins.
  - gp120—attachment to host CD4+ T cell.
  - gp41—fusion and entry.
- gag (p24)—capsid protein.
- pol—reverse transcriptase, aspartate protease, integrase.
Mechanism
- Reverse transcriptase synthesizes dsDNA from RNA
- dsDNA integrates into host genome.
- Virus…
  - binds CCR5 (early) or CXCR4 (late) co-receptor and CD4 on T cells
  - binds CCR5 and CD4 on macrophages.
Homozygous vs. heterozygous
- Homozygous CCR5 mutation = immunity.
- Heterozygous CCR5 mutation = slower course.

Question 17

Q

HIV diagnosis

Presumptive diagnosis
PCR/viral load tests
AIDS diagnosis
ELISA/Western blot tests

Answer

A

Presumptive diagnosis
- Made with ELISA
- Sensitive, high false-positive rate and low threshold, rule out test)
- (+) results are then confirmed with Western blot assay (specific, high false-negative rate and high threshold, rule in test).
HIV PCR/viral load tests
- Determine the amount of viral RNA in the plasma.
- High viral load associated with poor prognosis.
- Also use viral load to monitor effect of drug therapy.
AIDS diagnosis
- ≤ 200 CD4+ cells/mm3
  - Normal: 500–1500 cells/mm3
- HIV-positive with AIDS-defining condition (e.g., Pneumocystis pneumonia) or CD4 percentage < 14%.
ELISA/Western blot tests
- Look for antibodies to viral proteins
- These tests often are falsely negative in the first 1–2 months of HIV infection and falsely positive initially in babies born to infected mothers (anti-gp120 crosses placenta).

Question 18

Q

Time course of untreated HIV infection

Answer

A

Four stages of untreated infection:
- Flu-like (acute)
- Feeling fine (latent)
- Falling count
- Final crisis
During latent phase, virus replicates in lymph nodes.

Question 19

Q

Common diseases of HIV-positive adults:
As CD4+ count decrease…

Answer

A

Risk of reactivation of past infections (e.g., TB, HSV, shingles) increase
Dissemination of bacterial infections and fungal infections (e.g., coccidioidomycosis) increase
Non-Hodgkin lymphomas increase.

Question 20

Q

Common diseases of HIV-positive adults:
Clinical presentation

Systemic
Dermatologic
Gastrointestinal
Neurologic
Oncologic
Respiratory

Answer

A

Systemic
- Low-grade fevers, cough, hepatosplenomegaly, tongue ulcer
Dermatologic
- Fluffy white cottage-cheese lesions
- Hairy leukoplakia
- Superficial vascular proliferation
Gastrointestinal
- Chronic, watery diarrhea
Neurologic
- Abscesses
- Dementia
- Encephalopathy
- Meningitis
- Retinitis
Oncologic
- Non-Hodgkin lymphoma (large cell type)
- Primary CNS lymphoma
- Squamous cell carcinoma
- Superficial neoplastic proliferation of vasculature
Respiratory
- Interstitial pneumonia
- Invasive aspergillosis
- Pneumocystis pneumonia
- Pneumonia
- Tuberculosis-like disease

Question 21

Q

Common diseases of HIV-positive adults:
Systemic clinical presentation

For each
- Findings / labs
- Pathogen
Low-grade fevers, cough, hepatosplenomegaly, tongue ulcer

Answer

A

Low-grade fevers, cough, hepatosplenomegaly, tongue ulcer
- Findings / labs
  - Oval yeast cells within macrophages
  - CD4+ < 100 cells/mm3
- Pathogen
  - Histoplasma capsulatum (causes only pulmonary symptoms in immunocompetent hosts)

Question 22

Q

Common diseases of HIV-positive adults:
Dermatologic clinical presentation

For each
- Findings / labs
- Pathogen
Fluffy white cottagecheese lesions
Hairy leukoplakia
Superficial vascular proliferation

Answer

A

Fluffy white cottagecheese lesions
- Findings / labs
  - Pseudohyphae
  - Commonly oral if CD4+ < 400 cells/mm3
  - Esophageal if CD4+ < 100 cells/mm3
- Pathogen
  - C. albicans (causes oral thrush and esophagitis)
Hairy leukoplakia
- Findings / labs
  - Often on lateral tongue
- Pathogen
  - EBV
Superficial vascular proliferation
- Findings / labs
  - Biopsy reveals neutrophilic inflammation
- Pathogen
  - Bartonella henselae (causes bacillary angiomatosis)

Question 23

Q

Common diseases of HIV-positive adults:
Gastrointestinal clinical presentation

For each
- Findings / labs
- Pathogen
Chronic, watery diarrhea

Answer

A

Chronic, watery diarrhea
- Findings / labs
  - Acid-fast cysts seen in stool especially when CD4+ < 200 cells/mm3
- Pathogen
  - Cryptosporidium spp.

Question 24

Q

Common diseases of HIV-positive adults:
Neurologic clinical presentation

For each
- Findings / labs
- Pathogen
Abscesses
Dementia
Encephalopathy
Meningitis
Retinitis

Answer

A

Abscesses
- Findings / labs
  - Many ring-enhancing lesions on imaging
  - CD4+ < 100 cells/mm3
- Pathogen
  - Toxoplasma gondii
Dementia
- Findings / labs
  - Must differentiate from other causes
- Pathogen
  - Directly associated with HIV
Encephalopathy
- Findings / labs
  - Due to reactivation of a latent virus
  - Results in demyelination
  - CD4+ < 200 cells/mm3
- Pathogen
  - JC virus reactivation (cause of PML)
Meningitis
- Findings / labs
  - India ink stain reveals yeast with narrow-based budding and large capsule
  - CD4+ < 50 cells/mm3
- Pathogen
  - Cryptococcus neoformans
Retinitis
- Findings / labs
  - Cotton-wool spots on fundoscopic exam and may also occur with esophagitis
  - CD4+ < 50 cells/mm3
- Pathogen
  - CMV

Question 25

Q

Common diseases of HIV-positive adults:
Oncologic clinical presentation

For each
- Findings / labs
- Pathogen
Non-Hodgkin lymphoma (large cell type)
Primary CNS lymphoma
Squamous cell carcinoma
Superficial neoplastic proliferation of vasculature

Answer

A

Non-Hodgkin lymphoma (large cell type)
- Findings / labs
  - Often on oropharynx (Waldeyer ring)
- Pathogen
  - May be associated with EBV
Primary CNS lymphoma
- Findings / labs
  - Focal or multiple, differentiate from toxoplasmosis
- Pathogen
  - Often associated with EBV
Squamous cell carcinoma
- Findings / labs
  - Often in anus (men who have sex with men) or cervix
- Pathogen
  - HPV
Superficial neoplastic proliferation of vasculature
- Findings / labs
  - Biopsy reveals lymphocytic inflammation
- Pathogen
  - HHV-8 (causes Kaposi sarcoma)
  - Do not confuse with bacillary angiomatosis caused by B. henselae

Question 26

Q

Common diseases of HIV-positive adults:
Respiratory clinical presentation

For each
- Findings / labs
- Pathogen
Interstitial pneumonia
Invasive aspergillosis
Pneumocystis pneumonia
Pneumonia
Tuberculosis-like disease

Answer

A

Interstitial pneumonia
- Findings / labs
  - Biopsy reveals cells with intranuclear (owl eye) inclusion bodies
- Pathogen
  - CMV
Invasive aspergillosis
- Findings / labs
  - Pleuritic pain, hemoptysis, infiltrates on imaging
- Pathogen
  - Aspergillus fumigatus
Pneumocystis pneumonia
- Findings / labs
  - Especially with CD4+ < 200 cells/mm3
  - Ground-glass appearance on imaging
- Pathogen
  - Pneumocystis jirovecii
Pneumonia
- Findings / labs
  - Generally with CD4+ > 200 cells/mm3
- Pathogen
  - S. pneumoniae
Tuberculosis-like disease
- Findings / labs
  - Especially with CD4+ < 50 cells/mm3
- Pathogen
  - Mycobacterium avium–intracellulare, also known
    as Mycobacterium avium complex (MAC)

Question 27

Q

Prions

Prion diseases
PrPsc

Answer

A

Prion diseases
- Caused by the conversion of a normal (predominantly α-helical) protein termed prion protein (PrPc) to a β-pleated form (PrPsc), which is transmissible.
- It can be sporadic (Creutzfeldt- Jakob disease—rapidly progressive dementia), inherited (Gerstmann-Sträussler-Scheinker syndrome), or acquired (kuru).
PrPsc
- Resists protease degradation and facilitates the conversion of still more PrPc to PrPsc.
- Accumulation of PrPsc results in spongiform encephalopathy and dementia, ataxia, and death.