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Virology > Serology > Flashcards

Serology Flashcards

1
Q

Bartonella has 22 species. Three primarily infect humans. Faculative intracellular bacteria, gram negative

Which species cause each disease -

cat scratch disease

Carrion’s disease

Trench fever

A

Cat scratch - Bartonella henselae

Carrion’s disease - Bartonella bacilliformis

Trench fever -Bartonella quintana

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2
Q

What conditions can bartonella infection cause?

Usually mild/ self-limiting. Can cause severe infection in immunocompromised

A 
Common clinical information -
Lymphadenopathy
Retinitis
Culture negative endocarditis
PUO

Rarer causes -
Encephalitis
Glomerulonephritis

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3
Q

What is course of onset of cat scratch disease?

Bartonella henslae

A

Cat scratch causes macule in first week, which heals

Within 1-3 weeks - local lymph node swelling. Possibly general upset - fatigue, fever

Pus may develop within lymph nodes

Usually resolves spontaneously 2-4 months

Without treatment, low grade bacteraemia can persist

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4
Q

What is course of Carrion’s disease?

Bartonella bacilliformis

A

South America

Starts as Oroya fever - reddish purple nodules form. Fever, headache, disorientation. Can appear similar to malaria

Untreated, leaves skin lesions known as verruga peruana - reddish purple skin lesions

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5
Q

How are these infections transmitted?

Cat scratch

Carirons disease

Trench fever

A

Cat scratch - zoonosis - scratch cat/ dog. Fleas transmit between cats. 50% of cats have antibodies to bartonella

Carirons disease - sand fly - nocturnal (humans only host)

Trench fever - human body louse (humans only host)

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6
Q

How does Bartonella evade immune system?

A

Invades erythrocytes, and endothelial cells - where it replicates

Evades immune response

Without treatment, low grade bacteraemia can persist

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7
Q

How does Bartonella Henslae affect cats?

How to reduce infection rate in cats?

A

Cats usually asymptomatic

Carried by fleas, so use flea treatment to reduce population

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8
Q

Who is at risk of trench fever?

Found in Eastern Europe/ China

A

Homeless

Alcoholic

Poverty

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9
Q

How to diagnose bartonella infection?

A

CFT - NNUH uses immunofluorescent assay

PCR of biopsy

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10
Q

What is treatment of cat scratch disease?

A

May resolve spontaneously 2-4 months

Aspirate lymph node if suppurative

Azithromycin is treatment of choice

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11
Q

what is treatment of -

Carrions disease

Trench fever

A

Carrions disease - chloramphenicol/ ciprofloxacin

Trench fever - doxycycline

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12
Q

Mycoplasma pneumoniae lacks a cell wall, so does not gram stain. Means it is resistant to cell wall inhibitors e.g beta-lactams

Spread by respiratory droplet

Epidemics occur every 3-7 years, usually in Autumn

What virulence factors does it have?

A

Primarily lives on surface of respiratory epithelial cells, and can damage cilia preventing clearance

Can invade cells - allows to evade immune response/ drugs

Produces Community Acquired Respiratory Distress Syndrome (CARDS) toxin which leads to inflammation

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13
Q

What is incubation period of mycoplasma pneumonia?

What is treatment for mycoplasma pneumoniae?

A

1-4 weeks

Macrolides
Tetracyclines
Fluoroquinolones

Organism can persist for several weeks in oropharynx despite completion of antimicrobial therapy

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14
Q

When should testing be done for mycoplasma?

Immunofluorescence is semi-quantitative. What titre is significant?

A
  • Mycoplasma IgM rises usually by 7 days. So test 10-14 days after illness onset (IgM/IgA).
  • If taken too early, will have false negative IgM. If negative, consider re-testing in two weeks to see if rise in antibody response.
  • CFT titre 64 or greater is consistent with infection
  • If extra-pulmonary features, infection likely longer ago, and so CFT would be useful at any time
  • PCR testing of respiratory samples in acute setting
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15
Q

Symptoms are similar to other respiratory infection, except higher incidence of headache

What are extra-pulmonary symptoms of mycoplasma pneumoniae?

A

Encephalitis

Haemolytic anaemia

GI symptoms

Erythema multiforme/ SJS/ TEN

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16
Q

What percentage of cases of CAP are mycoplasma pneumoniae?

A

10-30%

80% of adults are IgG positive for mycoplasma

17
Q

GAS can cause various infections apart form pharyngitis/ scarlet fever

What are they?

A

Rheumatic fever

glomerulonephritis

cellulitis

reactive arthritis

erythema nodosum

18
Q

What tests are available for GAS?

Acute

Post-strep complications

A
  • Bacterial throat swab if acute
  • If rheumatic fever/ glomerulonephritis/ erythema nodosum - ASO/ ASD latex agglutination test

Anti-streptolysin-O (ASO) beta haemolytic exotoxin
Anti-streptodornase B (ASD)

  • ASO serology does not distinguish between group A, C, or G streptococci
  • ASD serology is specific for group A streptococci
19
Q

Results of ASO/ASD

What are normal values?

What is considered significant?

A

< 200 IU/ml are negative

> 200 IU/ml considered significant adults. Although up to 400 IU/ml can be considered normal in some cases
100 IU/ml considered significant children

If only slightly above 200 IU/ml, consider repeat sample. As two or more dilution rise in titre between acute and convalescent stage specimens should be considered significant

Significant result can be used to support a diagnose of post-streptococcal infection complication (rheumatic fever/ GN/ erythema nodosum)

20
Q

Results of ASO/ ASD

When do antibody levels rise?

When should testing be done in timeline of disease?

A

Following acute streptococcal infection, the ASO titre will usually rise after one week, increasing to a maximum level within 3 to 5 weeks and usually returning to the pre infection levels in approximately 6 to 12 months.

Test after 7 days of acute illness or test at anytime if presenting with rheumatic fever/ GN/ erythema nodosum. If acute GAS - perform bacterial swab

21
Q

Leptospirosis suspected.

What to test for?

A

Acute - blood/ urine for lepto IgM/ PCR at RIPL

After 7 days onset - blood for CFT IgG

22
Q

What are treatment options for leptospirosis?

A

Mild - doxycycline

Mod/severe - ceftriaxone/ penicillin

Do not recommend chemo-prophylaxis if exposure

23
Q

Leptospirosis is transmitted form rodents to humans directly, or via other pets e.g dogs.

Dogs are often vaccinated against leptospirosis.
>200 serotypes of leptospira, and different species are better at infecting certain mammals

What to do if dog has confirmed leptospirosis?

A

If asymptomatic, advise wear gloves and avoid contact with body fluids

If symptomatic - test for acute leptospirosis

Do not recommend chemo-prophylaxis if exposure, but not confirmed diagnosis. As most cases of leptospirosis are mild and self-limiting

Virology (56 decks)

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