The B. henselae Immunofluorescence Assay (IFA) is designed to detect human IgM and IgG antibodies to Bartonella henselae antigens in human serum. For diagnostic purposes, B. henselae IFA test results should be used in conjunction with other information available to the diagnosing physician.

Principal

The B. henselae IFA assay is a two-stage sandwich assay, based upon an antigen-antibody-complex formation involving the following steps:

• Binding of anti- henselae-specific antibodies in human serum to fixed B. henselae on a slide
• Binding of fluorescent-labeled anti-human IgG/IgM antibodies specific to the human anti–B. henselaeantibodies bound to fixed henselae on the slide.
• Identifying green fluorescing  henselae organisms with a fluorescent microscope

Clinical Significance

The B. henselae IFA is used to detect antibodies to B. henselae in human serum. Infections with B. henselae have been associated with Cat Scratch Disease, bacillary angiomatosis, peliosis hepatis, and bacteremia. Titers rise during the first two-to-four weeks of illness and decline over the next six-to-12 months. In patients with previously high titers, the presence of only IgG titer of less than 160 may indicate a resolving infection. If the IFA is negative but the clinical symptoms are present, PCR testing is suggested.

B. henselaeis most often transmitted to humans by cats. Recently, it has been suggested that B. henselaecan also be present in the same species of tick that transmits pathogens causing Lyme disease, Babesiosis, and Ehrlichiosis. Therefore, patients with positive titers should also be tested for the other tick-borne diseases.

Limitations

1. A negative IFA test result does not exclude the possibility of  henselae infection.
2. Results should be interpreted in conjunction with other laboratory and clinical findings.

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The Bartonella henselae Polymerase Chain Reaction (PCR) test is an assay that detects B. henselae-specific DNA in whole blood and/or cerebral spinal fluid (CSF). The combination of the following three steps imparts a very high specificity and sensitivity to the test:

• Hybridization/selection
• Amplification of Bartonella-specific DNA
• Detection of Bartonella-specific amplified DNA fragments

Reference Range

1. Negative:  henselaer DNA was not detected

Clinical Significance

The B. henselae PCR test is an assay that detects B. henselae-specific DNA in whole blood or cerebral spinal fluid. B. henselae ribosomal DNA (rDNA) fragments are hybrid-selected by probes, followed by PCR amplification of selected B. henselae rDNA. PCR products are confirmed by B. henselae-specific probes in a southern blot assay. The primers and probes used for the selection of B. henselaer DNA fragments are designed from published small subunit ribosomal RNA sequences.

Limitations

1. Results should be interpreted in conjunction with other laboratory and clinical findings.
2. Test results can only help the physician in confirming a clinical diagnosis.

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The Bartonella Fluorescent In-Situ Hybridization (FISH) assay is designed for qualitative detection of ribosomal RNA of the Bartonella directly in a blood smear. The test’s highest degree of specificity is provided by nucleic acid probes, which bind to RNA sequences of the pathogen.

Principal

The FISH assay is based on two fundamental principles:

1. Hybridization directly on a thin blood smear with a fluorescein-labeled Bartonella– specific probe
2. Identification of Bartonellaon a blood smear by viewing under a fluorescent microscope

Reference Range

Negative: No green fluorescing rod-shaped bacteria.

Clinical Significance

The Bartonella FISH assay is designed for qualitative detection of ribosomal RNA of bacteria belonging to the Genus Bartonella. Bartonella are rod-shaped, gram-negative bacteria. The FISH test provides a significant increase in specificity over standard gram stain for the presence of Bartonella in a whole blood smear. A positive result indicates the presence of bacterium from the Genus Bartonella, including B. berkhoffii, B. henselae, B. quintana, or B. vinsonii. The presence of an organism is a strong indication of the presence of disease. A positive result can aid in diagnosis during the course of the disease.

Limitations

1. A negative FISH test result does not exclude the possibility of Bartonella 
2. Results should be interpreted in conjunction with other laboratory and clinical findings.

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