# Bartonella

Bartonella is a genus of Gram-negative bacteria. It is the only genus in the family Bartonellaceae. Facultative intracellular parasites, Bartonella species can infect healthy people, but are considered especially important as opportunistic pathogens. Bartonella species are transmitted by vectors such as fleas, sand flies, and mosquitoes. At least eight Bartonella species or subspecies are known to infect humans.
Bartonella henselae is the organism responsible for cat scratch disease.

## History

Bartonella species have been infecting humans for thousands of years, as demonstrated by Bartonella quintana DNA in a 4000-year-old tooth. The genus is named for Alberto Leonardo Barton Thompson (1871–October 26, 1950), a Peruvian scientist.

## Infection cycle

Though some studies have found "no definitive evidence of transmission by a tick to a vertebrate host," Bartonella species are well-known to be transmissible to both animals and humans through various other vectors, such as fleas, lice, and sand flies. Bartonella bacteria are associated with cat-scratch disease, but a study in 2010 concluded, "Clinicians should be aware that ... a history of an animal scratch or bite is not necessary for disease transmission." All current Bartonella species identified in canines are human pathogens.

## Pathophysiology

Bartonella infections are remarkable in the wide range of symptoms they can produce. The course of the diseases (acute or chronic) and the underlying pathologies are highly variable.
Bartonella pathophysiology in humans :
| Species | Human reservoir or incidental host? | Animal reservoir | Pathophysiology | Distribution |
| B. bacilliformis | Reservoir | | Causes Carrion's disease (Oroya fever, Verruga peruana) | Peru, Ecuador, and Colombia |
| B. quintana | Reservoir | Japanese macaque | Causes trench fever, bacillary angiomatosis, and endocarditis | Worldwide |
| B. clarridgeiae | Incidental | Domestic cat | Cat scratch disease | |
| B. elizabethae | Incidental | Rat | Endocarditis | |
| B. grahamii | Incidental | Mouse | Endocarditis and neuroretinitis | |
| B. henselae | Incidental | Domestic cat | Cat scratch disease, bacillary angiomatosis, peliosis hepatis, endocarditis, bacteremia with fever, neuroretinitis, meningitis, encephalitis | Worldwide |
| B. koehlerae | Incidental | Domestic cat | | |
| B. naantaliensis | Reservoir | Myotis daubentonii | | |
| B. vinsonii | Incidental | Mouse, dog, domestic cat | Endocarditis, bacteremia | |
| B. washoensis | Incidental | Squirrel | Myocarditis | |
| B. rochalimae | Incidental | Unknown | Carrion's disease-like symptoms | |
| References: |||||

## Treatment

Treatment is dependent on which species or strain of Bartonella is found in a given patient. While Bartonella species are susceptible to a number of standard antibiotics in vitro—macrolides and tetracycline, for example—the efficacy of antibiotic treatment in immunocompetent individuals is uncertain. Immunocompromised patients should be treated with antibiotics because they are particularly susceptible to systemic disease and bacteremia. Drugs of particular effectiveness include trimethoprim-sulfamethoxazole, gentamicin, ciprofloxacin, and rifampin; B. henselae is generally resistant to penicillin, amoxicillin, and nafcillin.

## Epidemiology

Homeless intravenous drug users are at high risk for Bartonella infections, particularly B. elizabethae. B. elizabethae seropositivity rates in this population range from 12.5% in Los Angeles, to 33% in Baltimore, Maryland, 46% in New York City, and 39% in Sweden.

## Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN). The phylogeny is based on whole-genome analysis.