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M2 | Microbiolgy > Bacterial & Viral Lymphadenitis > Flashcards

Bacterial & Viral Lymphadenitis Flashcards

1
Q

Important properties of Epstein–Barr Virus (EBV)

A
  • Structurally similar to herpesviruses but antigenically different
  • Antigens :
    1. Viral Capsid Antigen (VCA): most important (diagnosis )

2- Early antigens (EA): produced before viral DNA synthesis (diagnosis)

3- Epstein-Barr nuclear antigen (EBNA): located in nucleus bound to chromosomes (diagnosis).

4- Lymphocyte-determined Membrane Antigen

5- Viral Membrane Antigen :
Neutralizing activity is directed against it

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2
Q

How is EBV is transmitted ?

A
  1. Exchange of saliva (e.g., during kissing)

2. Blood transmission (very rare)

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3
Q

How are the Nonspecific heterophil antibodies are found ?

A
  • Heterophil antibodies: are detected by tests using antigens different from antigens that induced them.
  • They agglutinate sheep or horse red blood cells in laboratory
  • Heterophil antibodies disappear within 6 months after recovery.
  • They are not specific for EBV (seen in hepatitis B & serum sickness.)
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4
Q

EBV infection modifies cell membrane constituent such that it becomes______ & induces______

A

Antigenic - heterophil antibodies

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5
Q

Where does EBV infection occur & infects which cells ?

A

Infection occurs in epithelial cells of oropharynx infects lymphoid cells (B lymphocytes)

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6
Q

How EBV remain latent ?

A

EBV remains latent within B lymphocytes (EBV DNA is in nucleus not integrated into cellular DNA)

  • Cytotoxic T lymphocytes react against infected B cells
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7
Q

IgM to VCA pathogenesis ?

A

IgM to VCA: first immune response ——> diagnosing acute infection

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8
Q

IgG to VCA pathogenesis?

A

IgG to VCA: persists for life ——-> past infection

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9
Q

Describe the life immunity in EBV

A

Lifetime immunity against infectious mononucleosis is due to antibody to viral membrane antigen

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10
Q

Clinical findings of EBV

A
  1. Infectious mononucleosis is characterized by
    * fever
    * sore throat
    * lymphadenopathy & splenomegaly
  2. Hepatitis is frequent
  3. Encephalitis occurs in some patients
  4. X- linked lymphoproliferative syndrome:
    * inherited immunodeficiency in children
    * severe, fatal, progressive form of infectious mononucleosis
  5. hairy leukoplakia
    * whitish, nonmalignant lesion with an irregular “hairy” surface on the lateral side of the tongue
    * in immunocompromised individuals
    * e.g. AIDS patients
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11
Q

Which diseases are associated with EBV ?

A
  1. Several cancers
    * Burkitt’s lymphoma, Hodgkin’s lymphoma and nasopharyngeal carcinoma) is associated with EBV infection
  2. Post-transplant lymphoproliferative disorder (e.g. B-cell lymphoma) is EBV-associated disease
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12
Q

State the Diagnostic tests for EBV

A
  1. Hematologic approach:
  2. Immunologic approach; two types of serologic tests
  3. Isolation EBV
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13
Q

What is the Hematologic approach?

A
  • Absolute lymphocytosis with 30% abnormal lymphocytes
  • Atypical lymphs are enlarged, have expanded nucleus & abundant, often vacuolated cytoplasm
  • They are cytotoxic T cells reacting against the EBV-infected B cells
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14
Q

Mention the types of serologic tests in EBV

A
  1. Heterophil antibody test:
  • Useful for early diagnosis of infectious mononucleosis because it is positive by week 2 of illness
  • Antibody titer declines after recovery not useful for detection of past infection
  1. EBV-specific antibody tests (difficult cases )
    - IgM VCA antibody detect ——> early illness
    - IgG VCA antibody detect —-> past infection
    - Antibodies to EA & EBNA can be useful diagnostically
    - Monospot test is used to detect heterophil antibody (more sensitive & specific & less expensive)
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15
Q

IgM VCA Ab detect ?

A

detect early illness

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16
Q

IgG VCA Ab detect ?

A

detect past infection

17
Q

Which test is more specific and inexpensive?

A

Monospot test

18
Q

Important properties of dengue virus

A
  • Single stranded RNA positive-strand virus

* have 4 serotypes

19
Q

Which organism/s transmit dengue virus ?

A

A. aegypti mosquito bite

  • jungle cycle : monkeys as reservoir & Aedes species as vectors
20
Q

Who is the reservoir in dengue fever ?

A

Human

21
Q

Clinical findings of classic dengue / breakbone fever

A
  • Sudden influenza like syndrome: fever, malaise, cough & headache
  • Severe pains in muscles joints (breakbone)
  • Enlarged lymph nodes & maculopapular rash & leukopenia
22
Q

Clinical features of Dengue Hemorrhagic Fever (severe)

A
  • Initial picture is same as classic dengue, hemorrhage, into gastrointestinal tract & skin
  • Hemorrhagic shock syndrome
23
Q

Why hemorrhagic shock syndrome takes place ?

A

is due to production of of cross reacting antibody in second dengue infection

24
Q

How patients recover from dengue hemorrhagic fever ?

A

recovers by one of four serotypes & antibody against that serotype is produced

25
Q

What happens when patients get infected again with another serotype ( 2ndry ) ?

A

occurs & large amounts of cross - reacting antibody to first serotype are produced

  • anamnestic
  • heterotypic response
26
Q

What are the 2 hypothesis abt Dengue Hemorrhagic Fever?

A
  1. Immune complexes : of virus & antibodies formed —-> activate complement ——-> increased vascular permeability & thrombocytopenia

2 . Antibodies increase entry of virus into monocytes & macrophages, with consequent liberation of large amount of cytokines

  • In either scenario, shock & hemorrhage result
27
Q

Laboratory diagnosis of dengue virus

A

1 Cell culture: Isolation of virus

  1. Serologic tests:
    - IgM antibody in acute sera
    - Fourfold or greater rise in antibody titer in convalescent sera.
  2. Polymerase chain reaction (PCR) assay: detects virus in blood
28
Q

Important features of Bartonella henselae

A
  • Small, pleomorphic gram-negative rod

* Fastidious organism & will not grow on routine blood agar

29
Q

How B. henselae is transmitted?

A
  1. Cat scratches or bites (main mode; oral flora of cats)
  2. Bite of cat fleas or exposure to cat urine or feces
  3. Person-to-person transmission (not significant)
30
Q

Cat scratch disease symptoms?

A

fever & tender, enlarged lymph nodes on same side as scratch

31
Q

Clinical findings in immunocompromised (AIDS) individuals ?

A
  1. Bacillary angiomatosis (raised, cherry-red vascular lesions in skin & visceral organs)
  2. Bacillary peliosis (peliosis hepatis) is similar to bacillary angiomatosis but lesions occur primarily in liver & spleen
32
Q

How to diagnose the cat scratch disease ?

A
  • Antibodies detected in patient’s serum
  • Culture on artificial media
  • 5 days or longer to grow
  • But its not usually dine
33
Q

Diagnosis of B.henselae

A

Pleomorphic rods in biopsy tissue using Warthin-Starry silver stain

34
Q

Important properties of Francisella tularensis

A

Small, pleomorphic gram-negative rod

35
Q

Mode of Transmission in Francisella tularensis

A
  • Reservoir : wild animals (rabbits, deer & rodents )
  • Humans are accidental “dead-end” hosts who acquire infection by bitten by ticks (Dermacentor) or by skin contact with animal
  • Rarely, organism is ingested in infected meat, causing gastrointestinal tularemia or inhaled causing pneumonia
36
Q

Pathogenesis of F.tularensis

A
  • It enters through skin, forming ulcer.
  • It localizes to cells of reticuloendothelial system ——-> granulomas
  • Caseation necrosis & abscesses.
  • Symptoms are caused primarily by endotoxin
37
Q

Clinical finding of F.tularensis

A
  1. Presentation vary from sudden onset of influenza like syndrome to prolonged onset of low-grade fever & adenopathy
  2. “Ulceroglandular” type: site of entry ulcerates & regional lymph nodes are swollen & painful
  3. Less frequent forms of tularemia:
    * glandular ( lymph node enlargement)
    * oculoglandular
    * typhoidal
    * gastrointestinal
    * pulmonary

4.Life long immunity

38
Q

How culture for F.tularensis is made ?

A
  • Rarely done (high risk to laboratory workers of infection by inhalation)
  • Cysteine- containing medium is used
39
Q

What other diagnosis methods for F.tularensis ?

A
  1. Agglutination test: serum samples in acute & convalescent phase
  2. Fluorescent-antibody staining of infected tissue

M2 | Microbiolgy (17 decks)

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