Investigations
1st investigations to order
serology: Bartonella henselae (cat-scratch disease [CSD])
Test
Serology can be negative early in the illness (<1 week); IgM turns negative by 3 months; IgG remains positive in 25% of patients beyond first year.
Two types are available:[31]
Indirect fluorescence assay (IFA): sensitivity: IgM 2% to 50%, IgG 14% to 100%; specificity: IgM 86% to 100%, IgG 34% to 100%
Enzyme immunoassay: sensitivity: IgM 60% to 85%, IgG 10% to 25%; specificity: IgM 98%, IgG 97%.
Result
positive test includes fourfold increase in titre between acute and convalescent phase; single IFA titre of ≥1:64 is considered positive
culture: B henselae (CSD)
Test
Colonies of Bartonella species may have two types of morphology: either rough and dry, raised, irregular colonies with whitish morphologic type, also described as verrucous or cauliflower-like appearance; or, smaller, moist, circular, tan colonies adhered to the agar plate giving a pitted appearance. Both variants can be present in the same culture. The morphology may differ with the species.[50]
Bartonella species are hard to grow in culture. Poor yield on culture of nodal aspirates.
Result
positive bacterial growth; may take 2 to 6 weeks
aspiration or biopsy of lymph nodes (CSD)
Test
Warthin-Starry's silver stain is useful to identify the organism.
Result
histopathological examination shows granuloma formation, micro-abscesses, follicular hyperplasia
serology: B quintana (trench fever)
Test
Various assays are available:[5][46]
1. Indirect immunofluorescence - a titre of >50 is considered positive; titres >800 are associated with bacteraemia and endocarditis[44][46]
2. Enzyme immunoassay
3. Complement fixation
4. Haemagglutination
5. Western Blot Assay (highly specific).
Result
positive titre (cut-off values vary by type of assay used)
culture: Bartonella quintana (trench fever)
blood smear (Carrion's disease)
Test
Better visualised with Romanowsky's, Giemsa's, or Wright's stains.
Result
intracellular coccoid or bacillary forms
culture: Bartonella bacilliformis (Carrion's disease)
Test
Requires semisolid agar with rabbit serum and haemoglobin, incubated at a lower temperature (25°C to 28°C; [77°F to 82°F]).
Result
positive bacterial growth; may take 5 to 30 days
serology: B bacilliformis (Carrion's disease)
Test
Various assays are available:[5]
1. Indirect immunofluorescence
2. Enzyme immunoassay
3. Complement fixation
4. Haemagglutination
5. Western Blot Assay (highly sensitive and specific)
Result
positive titre (cut-off values vary by type of assay used)
immunofluorescence antibody (IFA) assay: B vinsonii
Test
Serology by IFA for B vinsonii.
Result
positive
polymerase chain reaction (PCR) assay: B vinsonii
Test
PCR has been used for blood, cerebrospinal fluid, saliva, and periodontal specimen.
Result
positive
culture: B vinsonii
Test
Requires special enrichment medium (Bartonella alpha proteobacteria growth medium) for culture of blood and serum samples.[8]
Result
positive
Investigations to consider
PCR: B henselae (CSD)
Test
Lymph node, tissue sample such as heart valve, or blood sample can be sent for PCR analysis.
Sensitivity 43% to 76%; specificity 100%.
Helpful in rapid diagnosis when available.
Result
positive
tuberculin skin testing (TST)
Test
Negative result is part of the diagnostic criteria for Bartonella henselae infection, but does not rule out tuberculosis lymphadenopathy. A positive TST should be followed with appropriate diagnostic tests for tuberculosis lymphadenopathy.
Result
negative
interferon-gamma release assays (IGRA)
Test
IGRAs measure the release of interferon-gamma from T cells reacting to tuberculosis (TB) antigens; this is an ex vivo test to diagnose prior exposure to TB (e.g., latent TB infection [LTBI]). Like TST, its low sensitivity (60% to 80%) in diagnosing active TB and inability to distinguish between LTBI and active disease, limit its usefulness in the diagnosis of active TB.
Negative result is part of the diagnostic criteria for Bartonella henselae infection, but does not rule out tuberculosis lymphadenopathy.
A positive result should be followed with appropriate diagnostic tests for tuberculosis lymphadenopathy.
Result
negative
PCR: B quintana (trench fever)
Test
Tissue sample, including heart valves with vegetations, can be sent for PCR analysis. PCR can also be performed on blood for suspected bacteraemia.[17]
Helpful in rapid diagnosis when available.
Result
positive
tissue biopsy (trench fever)
Test
Immunohistochemistry and immunofluorescence are used for detecting B quintana in tissues such as heart valve in endocarditis or skin in bacillary angiomatosis.
Result
proliferative endothelial cells, positive immunochemistry or immunofluorescence stains
tissue biopsy (Carrion's disease)
Test
Biopsy specimen can also be sent for immunohistochemistry and culture of the organism.[5]
Result
histopathology shows proliferation of endothelium, monocytes, and macrophages; Warthin-Starry's stain reveals the organisms
echocardiogram
Test
Bartonella henselae may present as culture-negative endocarditis and is responsible for about 3% of endocarditis cases.[15] Usually involves aortic valves, and vegetations are found in 100% of cases.
B quintana may also present as culture-negative endocarditis, especially in urban homeless people.[5][17][42]
In acute infection with B bacilliformis (Oroya fever), patient may have evidence of pericarditis, such as a pericardial effusion. Case reports suggest B bacilliformis can also cause endocarditis, but this is rare.[17][47]
Result
vegetations are found in 100% of cases with Bartonella endocarditis; usually involves aortic valves; pericardial effusion
CT abdomen
Test
Liver involvement can occur in Bartonella henselae infection.
Immunocompetent children may present with hepatosplenic micro-abscesses secondary to Bartonella henselae infection. Immunocompromised patients may present with peliosis hepatis, characterised by dilated capillaries and blood-filled cavernous spaces in the liver.
Result
hepatosplenomegaly with micro-abscesses; peliosis hepatis
lumbar puncture with cerebrospinal fluid (CSF) analysis
Test
In patients with nuchal rigidity, CSF typically yields normal results, although pleocytosis and elevated protein may be present.
Result
usually normal
bone scan
Test
Osteomyelitis can occur in cases of Bartonella henselae infection.
Result
increased uptake if osteomyelitis present
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