Serology Flashcards
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
Cat scratch - Bartonella henselae
Carrion’s disease - Bartonella bacilliformis
Trench fever -Bartonella quintana
What conditions can bartonella infection cause?
Usually mild/ self-limiting. Can cause severe infection in immunocompromised
Common clinical information - Lymphadenopathy Retinitis Culture negative endocarditis PUO
Rarer causes -
Encephalitis
Glomerulonephritis
What is course of onset of cat scratch disease?
Bartonella henslae
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
What is course of Carrion’s disease?
Bartonella bacilliformis
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
How are these infections transmitted?
Cat scratch
Carirons disease
Trench fever
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)
How does Bartonella evade immune system?
Invades erythrocytes, and endothelial cells - where it replicates
Evades immune response
Without treatment, low grade bacteraemia can persist
How does Bartonella Henslae affect cats?
How to reduce infection rate in cats?
Cats usually asymptomatic
Carried by fleas, so use flea treatment to reduce population
Who is at risk of trench fever?
Found in Eastern Europe/ China
Homeless
Alcoholic
Poverty
How to diagnose bartonella infection?
CFT - NNUH uses immunofluorescent assay
PCR of biopsy
What is treatment of cat scratch disease?
May resolve spontaneously 2-4 months
Aspirate lymph node if suppurative
Azithromycin is treatment of choice
what is treatment of -
Carrions disease
Trench fever
Carrions disease - chloramphenicol/ ciprofloxacin
Trench fever - doxycycline
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?
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
What is incubation period of mycoplasma pneumonia?
What is treatment for mycoplasma pneumoniae?
1-4 weeks
Macrolides
Tetracyclines
Fluoroquinolones
Organism can persist for several weeks in oropharynx despite completion of antimicrobial therapy
When should testing be done for mycoplasma?
Immunofluorescence is semi-quantitative. What titre is significant?
- 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
Symptoms are similar to other respiratory infection, except higher incidence of headache
What are extra-pulmonary symptoms of mycoplasma pneumoniae?
Encephalitis
Haemolytic anaemia
GI symptoms
Erythema multiforme/ SJS/ TEN
What percentage of cases of CAP are mycoplasma pneumoniae?
10-30%
80% of adults are IgG positive for mycoplasma
GAS can cause various infections apart form pharyngitis/ scarlet fever
What are they?
Rheumatic fever
glomerulonephritis
cellulitis
reactive arthritis
erythema nodosum
What tests are available for GAS?
Acute
Post-strep complications
- 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
Results of ASO/ASD
What are normal values?
What is considered significant?
< 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)
Results of ASO/ ASD
When do antibody levels rise?
When should testing be done in timeline of disease?
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
Leptospirosis suspected.
What to test for?
Acute - blood/ urine for lepto IgM/ PCR at RIPL
After 7 days onset - blood for CFT IgG
What are treatment options for leptospirosis?
Mild - doxycycline
Mod/severe - ceftriaxone/ penicillin
Do not recommend chemo-prophylaxis if exposure
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?
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
