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Bartonella henselae and Bartonella quintana are small, rod-shaped, pleomorphic, gram-negative bacteria. The human body louse (Pediculus humanis) is the proposed vector for Bartonella quintana. No animal reservoir has been determined for Bartonella quintana. The domestic cat is believed to be both a reservoir and vector for Bartonella henselae. Cats may infect humans directly through scratches, bites, or licks, or indirectly through an arthropod vector. Humans remain the only host in which Bartonella infection leads to significant disease.
The sight of entry for Bartonella is through openings in the skin. Microscopically, Bartonella lesions appear as rounded aggregates that proliferate rapidly. These aggregates are masses of Bartonella bacteria. Warthin-Starry staining has shown that Bartonella organisms can be present within the vacuoles of endothelial cells, in macrophages, and between cells in areas of necrosis. Occasionally organisms are seen in the lumens of vessels. While cutaneous lesions are common, disseminated tissue infection by Bartonella has been seen in the blood, lymph nodes, spleen, liver, bone marrow, and heart.
Bartonella henselae has been associated with cat scratch disease (CSD), peliosis hepatitis (PH), and endocarditis. Bartonella quintana has been associated with trench fever, bacillary angiomatosis (BA), and endocarditis. Both can cause BA, a newly recognized syndrome. BA is a vascular proliferative disease usually involving the skin and regional lymph nodes.
CSD begins as a cutaneous papule or pustule that usually develops within a week after an animal contact. Regional lymphadenopathy, which follows, is the predominant clinical feature of CSD. Skin testing has been used in the past for CSD, but no skin test has been licensed for routine use.
Trench fever, which was a problem during World War I and World War II, is characterized by a relapsing fever and severe pain in the shins.
Interest in Bartonella quintana and Bartonella henselae has recently increased since its presence in AIDS patients and transplant patients has been documented. PH and febrile bacteremia syndrome are both syndromes that have afflicted patients with AIDS or those patients that are immunocompromised.
While trench fever and CSD are usually self-limiting illnesses, the other Bartonella-associated diseases can be life-threatening.
Rapid diagnosis of Bartonella infection, especially in the context of a cat scratch or histopathology showing typical features of stellate microabscesses and/or positive Warthin-Starry stain
A positive immunofluorescence assay (IFA) IgM (titer >1:20) suggests a current infection with either Bartonella henselae or Barteonella quintana.
A positive IgG (titer >1:128) suggests a current or previous infection. Increases in IgG titers in serial specimens would indicate an active infection.
Normal serum specimens usually have an IgG titer of <1:128. However, 5% to 10% of healthy controls exhibit a Bartonella henselae and Bartonella quintana titer of 1:128. No healthy controls showed titers of > or =1:256. IgM titers from normal serum were found to be <1:20. IgM titers at > or =1:20 have not been seen in the normal population.
Culture should also be considered, but this may not be an optimal method due to slow growth and fastidious nature of the organism.
IgG cross-reactivity between Bartonella henselae and Bartonella quintana has been reported. However, the infecting species will usually have the higher titer.
IgM cross-reactivity is usually not seen. Significant cross-reactions have been reported between Bartonella species and Chlamydia species.
1. Maurin M, Raoult D: Bartonella (Rochalimaea) quintana infections. Clin Microbiol Rev 1996;9:273-292
2. Maurin M, Birtles R, Raoult D: Current knowledge of Bartonella species. Eur J Clin Microbiol Dis 1997;16:487-506