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      Drugs & Diseases > Infectious Diseases

      Trench Fever Workup

      Updated: Jan 17, 2020
      • Author: Sarah Perloff, DO, FACP; Chief Editor: John L Brusch, MD, FACP  more...
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      Workup

      Approach Considerations

      B quintana infection is difficult to diagnose in the laboratory. Therefore, the microbiology laboratory must be consulted to maximize the diagnostic yield.

      Blood cultures have poor sensitivity for detecting B quintana. Serologic testing is also unhelpful because of poor specificity resulting from frequent cross-reactivity with other organisms, and testing is further hampered by inadequate immune responses in immunocompromised individuals.

      PCR-based genomic testing is sensitive and specific but is technically demanding. Therefore, the microbiology laboratory must be consulted to maximize the diagnostic effort.

      Skin lesions suspicious for bacillary angiomatosis should be biopsied to allow for histopathologic evaluation with or without tissue PCR analysis.

      Transthoracic and/or transesophageal echocardiography can identify the presence of valvular vegetations in cases of Bartonella endocarditis.

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      Laboratory Studies

      Blood cultures obtained for the diagnosis of Bartonella infection are typically low-yield procedures in most laboratories. The Clinical Laboratory Standards Institute notes that lysis-centrifugation techniques in combination with inoculation of fresh enriched chocolate agar are optimal. [47] The plates should be incubated at 35°C in a humid, carbon dioxide–rich environment for 14-21 days.

      Newer broth lytic systems can be used for a 7-day incubation period, followed by subculture onto enriched chocolate media in a humid, carbon dioxide–rich environment at 35°C for 21 days. An older protocol using BACTEC blood culture bottles involves staining with acridine orange after 7 days of incubation. [48] If organisms are seen, blood or chocolate subcultures are incubated at 37°C in a humid, carbon dioxide–rich environment for up to 4 weeks.

      Immunofluorescent assays (IFAs) for immunoglobulin M (IgM) and immunoglobulin G (IgG) antibody levels for both B quintana and B henselae are available in most reference laboratories and some tertiary care centers. These antibody tests may cross-react and should therefore be quantitated in tandem for comparison to establish a diagnosis. [10] Serologic cross-reactivity between antibodies against B quintana and those against Chlamydia pneumoniae and Coxiella burnetii is common. [10, 49, 37, 34] Acute and convalescent IFA titers for each of these organisms can be diagnostic.

      Enzyme immunoassay (EIA) and enzyme-linked immunosorbent assay (ELISA) techniques have been described and are available in some laboratories.

      Serologic testing is positive for antibodies (IgG titers >1/50) to B quintana in many patients with trench fever, urban trench fever, Bartonella bacteremia, or angioproliferative disease. Such testing is helpful for diagnosis and seroprevalence studies. [20, 27] The highest levels of antibodies are found in patients with Bartonella endocarditis (IgG titers >1/800). [20] Patients with chronic Bartonella bacteremia have low or absent antibody levels.

      Several PCR-based genomic assays and histochemical stains that allow direct detection of Bartonella DNA in both tissue and blood have been developed. These are very specific when results are positive. [10] Detection of B quintana DNA in vegetations from immunocompetent patients is essential in the diagnosis of endocarditis. Bartonella DNA testing via PCR is available at the Centers for Disease Control and Prevention (CDC) and at most reference laboratories.

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      Histologic Findings

      Biopsy of skin lesions in patients with Bartonella infection shows perivascular lymphocytic infiltrates with some inflammatory cells. Bartonella organisms can be detected in the interstitial tissues. Lesions may also involve liver, spleen, bone marrow, and lymphatic tissues. [10]

      The histology of enlarged lymph nodes reveals a noncaseating granulomatous reaction similar to that seen in catscratch disease. [10] Bartonella organisms cannot be demonstrated via light microscopy.

      The pathology of involved cardiac valvular tissue reveals a destructive mononuclear inflammatory reaction with focal calcifications. [10] Bartonella organisms can be detected with PCR techniques.

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