Microbiology - Virology Flashcards Preview

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Flashcards in Microbiology - Virology Deck (122):
1

Naked virus with icosahedral capsid components

Capsid + Nucleic acid

2

Enveloped virus with icosahedral capsid

Surface protein
Lipid bilayer
Capsid
Nucleic acid

3

Enveloped virus with helical capsid

Surface protein
Lipid bilayer
Helical capsid with nucleic acid inside

4

Recombination

exchange of genes between two chromosomes by crossing over within regions of significant base sequence homology

5

Reassortment

when viruses with SEGMENTED genomes (e.g. influenza virus) exchange segments. High-frequency recombination.
- Cause of influenza pandemics

6

Complementation

when 1 of 2 viruses that infect cell has a mutation that results in nonfunctional protein
Nonmutated virus "complements" the mutated one by making a functional protein that serves both viruses

7

Phenotype mixing

- occurs co-infection of a cell by two viruses
Genome of virus A can be partially or completed coated (forming pseudovirion) with surface proteins of virus B
Type B protein coat determines infectivity (tropism) of hybrid virus
- Progeny from infection have a type A coat that is encoded in type A genetic material

8

Live attenuated viruses

induce humoral and cell-mediated immunity but have reverted back to virulence on rare occasions

9

Examples of live attenuated viruses

-Smallpox
- Yellow fever
- Chickenpox (VZV)
- Sabin's polio virus
- MMR
- Influenza (intranasal)

10

Killed virus vaccine

induce only humoral immunity but are stable

11

Examples of killed viruses

Rabies
Influenza (injected
Salk Polio
HAV vaccines

12

Recombinant

HBV antigen (antigen = HBsAg), HPV (6, 11, 16, 18)

13

DNA viral genomes

All DNA viruses except PARVOVIRIDAE are dsDNA
- all are linear except (PAPILLOMA-, POLYOMA-, and HEPADNAVIRUSES [circular])

14

Parvovirus

ssDNA

15

RNA viral genomes

All RNA viruses except Reoviridae are ssRNA

16

Reoviridae

dsRNA

17

Positive stranded RNA viruses

"I went to a "RETRO" "TOGA" partry where I drank "FLAV"ored "CORONA" and ate "HIPPY" "CALI"fornia "PIC"kles
- Retrovirus
- Togavirus
- Flavovirus
- Coronavirus
- Hepevirus
- Calcivirus
- Picornavirus

18

Infectious naked viral genomes

purified nucleic acids of most dsDNA (except poxviruses and HBV) and (+) ssRNA viruses are infectious.

19

Non-infectious naked viral genomes

- Naked nucleid acids of (-) ssRNA and dsRNA viruses are not infectious. They need polymerases contained in complete virion

20

Virus ploidy

all viruses are haploid (with 1 copy of DNA or RNA) except retroviruses, which have 2 identical ssRNA molecules (= diploid)

21

DNA virus replication

all replicate within nucleus (except poxvirus)

22

RNA virus replication

all replicate in the cytoplasm (except influenza virus and retroviruses)

23

Viral envelopes

Give "PAPP" smears and "CPR" to a "NAKED HEPP"y
Naked include
- Papillomavirus
- Adenovirus
- Picornavirus
- Polyomavirus
- Calcivirus
- Hepevirus

24

DNA viruses

"HHAPPPPy"
H= Hepadna
H= Herpes
A = Adenoviruses
P = Pox
P = Parvo
P = Papilloma
P = Polyoma

25

DNA virus characteristics

- double stran ded (except parvovirus)
- linear (except papolloma, polyoma, and hepadna)
- are icosahedral except poxvirus
- replicate in the nucleus party (except pox)

26

Herpesviruses

- enveloped
- ds and linear

27

HSV-1

- oral (and some genital lesions), spontaneous temporal lobe encephalitis (most common cause of spontaneous encephaltitis in US)
keratoconjunctivitis
- Latent in trigeminal ganglia
- transmitted through respiratory and saliva secretions

28

HSV-2

- Herpes genitalis
- Neonatal herpes
- Latent in sacral ganglia
- transmitted via sexual contact, perinatal

29

VZV

Varicella-zoster (chicken pox, shingles)
- Encephalitis
- Pneumonia
- Latent in dorsal root or trigeminal ganglia
- transmitted via respiratory secretions

30

EBV

HHV-4
- mononucleosis
- Burkitt's lymphoma
- Hodgkin's lymphoma
- Nasopharyngeal carcinoma
- Latent in B cells

31

CMV

Congenital infection
Mononucleosis (negative monospot) - immunocompetent patietnts
Pneumonia
Retinitis
Infected cells have "owl's eye" inclusions
- Latent in mononuclear cells

32

HHV-6

Roseola
High fevers for several days that can cause seizures, followed by a diffuse macular rash

33

HHV-8

Kaposi's sarcoma (HIV patients)

34

Hepadnavirus

-enveloped
- double stranded and partial circular
- acute or chronic hepatitis
- vaccine available - contains HBV surface antigen
- not retrovirus but has reverse transcriptase

35

Adenovirus

- non-enveloped
- double stranded and linear
- febrile pharyngitis - sore throat; acute hemorrhagic cystitis
- pneumonia
- conjunctivitis

36

Parvovirus

- non- enveloped
- single stranded and linear negative DNA
- B19 - aplastic crises in sicke cell disease, "slapped cheeks" rash in children - erythema infectiosym (fifth disease)
- RBC destruction in fetus leads to hydrops fetalis and death
- Pure RBC aplasia and rheumatoid arthritis-like symptoms in adults

37

Papillomavirus

- non-enveloped
- double stranded and circular
- HPV - warts (1,2,6,11)
- Cervical cancer (16, 18)
- Vaccine is available

38

Polyoma virus

- non-enveloped
- double stranded and circular
JC virus - associated with PML in HIV
BK virus - transplant patients, commonly kidney

39

Poxvirus

- enveloped
- double stranded and linear (largest DNA virus)
- smallpox
- vaccinia (cowpox)
- molluscum contagiosum - flesh colored dome lesions with central dimple

40

HSV identification

PCR is test of choice
Tzanck test - a smear of an opened skin vesicle to detect multinucleated giant cells seen HSV-1, HSV-2, and VZV
** Infected cells have intranuclear Cowdry A inclusions

41

EBV

A herpesvisus
- can cause mononucleosis, hepatosplenomegaly, pharyngitis, and lymphadenopathy
- peak incidence (15 - 20 y.o)
- Atypical lymphocytes seen in peripheral smear are not infected B cells but rather cytotoxic T cells
- Positive Monospot test
- associated with Hodgkin's, Burkitt lymphomas as naseopharyngeal carcinoma

42

Positive Monospot

- heterophile antibodies detected by agglutination of sheep/horse RBCS

43

Reoviruses

- nonenveloped
- linear dsRNA with 10-12 segments
- icosahedral (double)
- Coltivirus - Colorado tick fever
- Rotavirus - #1 cause of fatal diarrhea in children

44

Picornaviruses

- non-enveloped
+ SS linear RNA
- icosahedral
"PERCH"
Poliovirus
Echovirus
Rhinovirus
Coxsackievirus
Hep A virus

45

Hepevirus

-non-enveloped
+ SS linear RNA
- icosahedral
HEV

46

Calciviruses

- nonenveloped
- SS + linear RNA virus
- icosahedral capsid
- Norovirus - viral gatsroenteritis

47

Flaviviruses

- enveloped SS + linear RNA
- icosahedral
- HCV
- Yellow fever
- Dengue
- St. Louis encephalitis
- West Nile virus

48

Togaviruses

- enveloped
- SS + linear RNA and icosahedral
- Rubella
- Eastern & Western equine encephalitis

49

Retroviruses

-enveloped
- SS + linear RNA
- icosahedral
- have reverse transcriptase
- HTLV - T-cell leukemia
- HIV - AIDS

50

Coronaviruses

enveloped SS + linear RNA
Helical
Common cold and SARS

51

Orthomyxoviruses

Enveloped
SS - linear RNA
8 segments
Influenza virus

52

Paramyxoviruses

Enveloped SS - linear RNA
Nonsegmented
Parainfluenza - croup
RSV - bronchiolitis in babies - treated w/ ribavirin
Measles
Mumps

53

Rhabdoviruses

Enveloped
SS - linear RNA
Helical
Rabies

54

Filoviruses

Enveloped
SS - linear RNA
Helical
Ebola/Marbug hemorrhagic fever - often fatal!

55

Arenaviruses

Enveloped
SS - CIRCULAR RNA
2 segments
Helical
LCMV - lymphocytic choriomeningitic virus
Lassa fever encephalitis - spread by mice

56

Bunyaviruses

Enveloped
SS - CIRCULAR RNA
3 segments
Helical
California encephalitis
Sandfly/Rift valley fevers
Crimean-Congo hemorrhagic fever
Hantavirus - hemorrhagic fever, pneumonia

57

Delta virus

Enveloped
SS - CIRCULAR RNA
Uncertain capsid
HDV - defective virus that requires HBV co-infection

58

Negative stranded viruses

must transcribe negative strand to positive
Virion brings its own RNA-dependent RNA polymerase

59

Mneumonic for negative stranded viruses

"Always Bring Polymerase Or Fail Replication"
A = Arenaviruses
B = Bunyaviruses
P = Paramyxoviruses
O = Orthomyxoviruses
F = Filoviruses
R = Rhabdoviruses

60

Segmented viruses

All are RNA viruses
"BOAR"
B = Bunyavirus
O = Orthomyxoviruses (influenza viruses)
A = Arenavirueses
R = Reoviruses

61

Picornaviruses

Poliovirus
Echovirus
Rhinovirus
Coxsackievirus
Hepatitis A

62

Picornaviruses

RNA is translated into 1 large polypeptide that is cleaved by proteases into functional viral proteins
- Can cause viral meningitis (EXCEPT Rhinovirus and HAV)
- All are enteroviruses (fecal-oral spread) except rhinovirus

63

Rhinovirus

A picornavirus
Non-enveloped RNA virus
Causes common cold
> 100 serologic types
Acid labile - destroyed by stomach acid
Doesn't infect GI tract (unlike other picornaviruses)

64

Yellow fever virus

Flavivurs (also an arbovirus)
- transmitted by Aedes mosquitos
- Has monkey or human resevoir
Sx: high fever, black vomitis, and jaundice

65

Rotavirus

Common WORLDWIDE cause of infantile gastroenteritis
- segmented dsRNA virus
- major cause of acute diarrhea during winter esp. in day care centers, kindergartens
- villous destruction with atrophuy leads to decreased absorption of NA and loss K

66

Influenza viruses

Orthomyxoviruses
Enveloped, negative ss RNA viruses with 8 segments
Hemagglutinin - promotes viral entry
Neuraminidase - promotes progeny virion release
- patient at risk for fatal bacterial superinfection
Rapid genetic changes

67

Mode of protection from influenza viruses

Killed viral vaccine is MAJOR mode of protection
Another vaccine contains live, temp sensitive mutant that replicates in the nose but not in lung

68

Genetic shift/antigenic shift

- causes pandemics
- reassortment of viral genome
- segments undergo high-frequency recombination such as human flu A virus with swine flu A virus

69

Genetic drift

- causes epidemics
- minor (antigenic drift) - changes based on random mutation

70

Rubella virus

togavirus
causes rubella, known as German measles
- Fever, posterior auricular lymphadenopathy,
- Truncal rash that starts at head and descends
- causes mild disease in children but serious congenital disease

71

Paramyxovirus

- disease in children
- parainfluenza (croup: seal-like barking cough)
- Mumps, Measles
- Contain surface F protein, which causes respiratory epithelial cells to fuse and form multinucleated cells

72

RSV

Paramyxovirus - causes brionchiolitis, pneumonia in infants
Palivizumab (monoclonal antibody against F portein) prevents pneumonia caused by RSV infection in premature infants

73

Measles

paramyxovirus
- Kolik spots (red spots with blue-white cente on buccal mucosa)
- descending maculopapular rash
- subacute sclerosing panencephalitis and giant cell pneumonia (in immunosuppresed)
- rash presents last and spreads from head to toe, includes hands and feet (vs. trunk in Rubella)

74

3 C's of Measles

Cough
Coryza (rhinitis, inflammation of nasal mucosa)
Conjunctivitis

75

Mumps

Paramyxovirus
Parotitis
Orchitis (inflammation of testes)
Asceptic meningitis
- Can cause sterility in puberty

76

Paramyxovirus
Parotitis
Orchitis (inflammation of testes)
Asceptic meningitis
- Can cause sterility in puberty

Bullet-shaped virus
- Negri bodies - cytoplasmic inclusions in neurons infected by rabies virus
- Found in Purkinke cells of cerebellium

- Post exposure treatment is wound cleansing and vaccine with/without rabies immunoglobulin

77

Rabies

- Has long incubation period (weeks to months) before symptom onset
- Travels to CNS by migrating in a retrograde fashion up nerve axons
- Progression of disease: fever, malaise --> agitation, photophobia, hydrophobia --> paralysis, coma --> death
- Associated with bat, raccoon, skunk bites than dog bites in US

78

Hep A virus

RNA picornavirus
- transmitted fecal-orally
- no carries
- short incubation (weeks)
- no HCC risk
- assymptomatic, acute, alone

79

HBV

DNA hepadnavirus
- transmitted parentally, sexually, maternal-fetal
- carrier state possible
- long incubation (months)
- HCC risk as it integrates with host genome and acts as oncogene

80

HCV

RNA flavivirus
- transmitted primarily in blood, IV drug users, post-transfusion
- carrier state
- long incubation
- HCC risk from chronic inflammation
- associated with cryoglobulin

81

HDV

RNA deltavirus
transmission: Parental, Sexual, Maternal-Fetal
Carrier state
-Superinfection (after chronic HBV)
- Co-infection (with acute HBV)
- defective virus, dependent on HBV

82

HEV

RNA hepevirus
- transmitted fecal orally, especially with waterborne epidemics
- no carrier ste
- short incubation
- no HCC risk
- high mortality in pregnent women

83

Anti-HAV (IgM)

IgM antibody to HAV, best test to detect active Hep A

84

Anti-HAV (IgG)

IgG antibody indicates prior HAV infection and/or prior vaccination; protects against new infection

85

HBsAg

antigen found on surface of HBV
indicates HBV infection

86

Anti-HBsAg

antibody to HBsAg
- indicates immunity to Hep B

87

HBcAg

Antigen associated with core of HBV

88

Anti-HBV

antibody to HBcAg
IgM = acute/recent infection
IgG = prior exposure or chronic infection

89

HBeAg

indicates active viral HBV replication and thus high transmissibility

90

Anti-HBe

antibody to e antigen; indicates low transmissibility

91

Window period

- can occur 5-6 months after exposure
- no HBsAg but Anti-HBe Anti-HBcIgM

92

HIV

diploid genome (2 molecules of RNA)
reverse transcriptase synthesizes dsDNA from RNA
dsDNA integrates into host genome
- virus binds to CCR5 (early) or CXCR4 (lates) co-receptor and CD4 on T cells
- binds to CCR5 and CD4 on macrophages

93

Homozygous CCR5 mutation

= immmunity from HIV

94

Heterozygous CCr5 mutation

= slower course of HIV

95

Structural proteins associated with HIV

- env (gp 120 and gp41) - formed from cleavage of gp160 to form envelope proteins
- gp120 - attachment to CD4+ T cells
- gp41 - fusion and entry
-gag (p24) - capsid protein
pol - reverse transcriptase, aspartate protease integrase

96

HIV diagnosis

- intially with ELISA (high sensitivity, low specificity)
- confirmed with Western blot (high specificity)

97

HIV/PCR viral load

tests determine the amount of viral RNA in plasma.
High viral load associated with poor prognosis
Also use viral load to monitor drug therapy

98

AIDS diagnosis

< 200 CD4
- HIV with AIDS defining condition (e.g PCP pneumonia)
- CD4/CD8 < 1.5

99

ELISA/Western blot

looks for antibodies to viral proteins
are often falsely negative in the first 1-2 months of HIV infection
- Falsely positive initially in babies born to infected mothers (anti-gp120 crosses placenta)

100

Four stages of infection

1. Flu-like (acute)
2. Feeling fine (latent) - virus is replicating in lymph nodes
3. Falling count
4. Final crisis

101

HIV + with low grade fevers, cough, hepatosplenomegaly, tongue ulcer

Histoplasmosis capsulatum
- causes pulm symptoms in "healthy" patients
- oval yeast cells within macrophages, CD4 < 100

102

HIV + w/ fluffy white cottage cheese lesions

C. albicans
- pseudohyphase
- oral if CD4 < 400
- esophageal if CD4 < 100

103

HIV + w/ superficial vascular proliferation

Bartonella henselae (causes bacillary angiomatosis)
- biopsy shows neutrophilic inflammation

104

HIV+ w/ chronic watery diarrhea

Cryptosporidium
- acid fast cysts seen in stool when CD4 < 200

105

HIV + w/ encephalopathy

- JC virus reactivation (cause of PML)
- results in demyelination of oligodendrocytes CD4 < 200

106

HIV + w/ brain abscesses

Toxoplasmosis gondii
- many ring-enhancing lesions on imaging
- CD4 < 100

107

HIV+ w/ meningitis

- C. neoforms
- India ink stain reveals yeast with narrow-based budding and large capsule
- CD4 < 50

108

HIV + w/ retinitis

CMV
- cotton wool sports on fundoscopic exam and may occur with esophagitis
CD4 < 50 cells

109

HIV + dementia

Directly associated with HIV
- may have differentiate from other causes

110

HIV + with superficial neoplastic proliferation of vasculature

HHV-8 (Kaposi's sarcoma)
- biopsy reveals lymphocytic inflammation
** don't confuse with bacilliary angiomatosis

111

HIV + with hairy leukoplakia

EBV
- often on lateral tongue

112

HIV+ w/ non-Hodgkin's lymphoma

EBV
- often on oropharynx (Waldeyer's ring)

113

HIV+ w/ squamous cell carcinoma (of anything!!)

HPV
- in gay men, may have anal HPV

114

HIV + with primary CNS lymphoma

EBV
- multiple or focal, differentiate from toxoplasmosis

115

HIV + with interstitial pneumonia

CMV
- biopsy reveals cells with intranuclear (owl's eye) inclusion bodies

116

HIV + with invasive aspergillosis

Aspergilosis fumigatus
- pleuritic pain, hemoptysis, infiltrates on imaging (acute angled hyphae)

117

HIV+ with pneumonia

Pneumocystis jirovecci
- especially in CD4 < 200 cells

118

HIV + with TB-like disease

Mycobacterium avium-intracelluaire
- esp in CD4 < 50 cells

119

Envelope proteins for HIV

- acquired from budding from host cell plasma membrane
- gp120: docking protein for attachment to CD4
- gp41: transmembrane protein for fusion and entry

120

Gap(p24) protein

HIV capsid protein

121

p17 associated with HIV

Matrix protein

122

pol gene

HIV
- reverse transcriptase
- aspartate protease
- integrase