Bartonella Henselae
Bartonella henselae is a small, pleomorphic Gram-negative bacillus that is difficult to culture due to its fastidious growth requirements. This organism has been associated with:
- Cat scratch disease
- Bacillary angiomatosis
- Peliosis hepatitis
- Endocarditis
The domestic cat is both the reservoir and vector for Bartonella henselae. The bacillus is transmitted to humans by domestic cat scratches, bites, or licks. Cat scratch disease begins as a cutaneous pustule that develops during the first week after contact with a cat, followed by regional lymphadenopathy. Most cases are self-limited.
Traditionally, the diagnosis of Bartonella infections has been made by Warthin-Starry staining of tissue and serology. The Euroimmun indirect immunofluorescence test is a standardized assay for the determination of specific antibodies against Bartonella henselae. A positive IgM (titer >1:20) suggests a current infection. A positive IgG (titer >1:128) suggests a current or previous infection. Between 5 and 10% of healthy individuals have an IgG titer of 128.
Because tissue staining and serology are nonspecific and may be falsely negative in early stages of disease, real time PCR testing for the citrate synthase gene of Bartonella species has become the preferred test. A positive PCR result does not differentiate between Bartonella henselae and Bartonella quintana.
Specimen requirement for serology is a red top tube of blood. Specimen requirement for PCR is:
- A lavender top tube of blood
- Fresh tissue frozen in a screw-capped sterile plastic container
- Paraffin block of tissue
