Bartonella*

The genus Bartonella is a branch of alphaproteobacteria in the Rhizobiales order and the Bartonellaceae family. The genus represents a union with bacteria formerly in the genera Rochalimaea and Grahamella, whose members are small facultatively intracellular Gram-negative bacilli and coccobacilli. Members of the genus are zoonotic agents, for which arthropods are often reservoirs and vectors. At least 32 species are validly described, including 12 of which are definite or potential human pathogens. The most important of these are B. bacilliformis, B. quintana, B. elizabethae, and B. henselae. These are the agents for a variety of human illnesses, such as Oroya fever and Carrion’s disease, trench fever, cat scratch disease, and endocarditis among immunocompetent patients and bacillary angiomatosis/peliosis among those who are immunocompromised. Bartonella species infections are also common among domestic pets and wild animals. Diagnostic test methods include culture, serology, and molecularly based assays. The slow growth and fastidious nature of some species necessitates the use of molecular and/or serologic tests for most applications, but commercially available tools are lacking. While approaches to determine antimicrobial resistance are described, most antibiotics that are sensitive are bacteriostatic only, and there is often no correlation between in vitro susceptibility test results and clinical responses.