| Bartonella | |
|---|---|
| Scientific classification | |
| Kingdom: | Bacteria |
| Phylum: | Proteobacteria |
| Class: | Alpha Proteobacteria |
| Order: | Rhizobiales |
| Family: | Bartonellaceae |
| Genus: | Bartonella Strong et al., 1915 |
| Species | |
|
B. alsatica |
|
Bartonella (formerly known as Rochalimaea) is a genus of Gram-negative bacteria. Facultative intracellular parasites, Bartonella species can infect healthy people but are considered especially important as opportunistic pathogens.[1] Bartonella are transmitted by insect vectors such as ticks, fleas, sand flies and mosquitoes. At least eight Bartonella species or subspecies are known to infect humans.[2] In June 2007, a new species of the genus, called Bartonella melophagi, was discovered. This is the sixth species known to infect humans, and the ninth species and subspecies, overall, known to infect humans.
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Bartonella species have been infecting humans for thousands of years, as demonstrated by Bartonella quintana DNA in a 4000 year old tooth.[3] The genus is named for Alberto Leonardo Barton Thompson, a Peruvian scientist born in Argentina.
The currently accepted model explaining the infection cycle holds that the transmitting vectors are blood-sucking arthropods and the reservoir hosts are mammals. Immediately after infection, the bacteria colonize a primary niche, the endothelial cells. Every five days, a part of the Bartonella in the endothelial cells are released into the blood stream where they infect erythrocytes. The bacteria then invade and replicate within a phagosomal membrane inside the erythrocytes. Inside the erythrocytes, the bacteria multiply until they reach a critical population density. At this point, the Bartonella has simply to wait until it is taken with the erythrocytes by a blood-sucking arthropod. Though some studies have found "no definitive evidence of transmission by a tick to a vertebrate host," [4] [5] Bartonella species are well-known to be transmissible to both animals and humans through various other vectors such as fleas, lice, and sandflies. [6] Recent studies have shown a strong correlation between tick exposure and bartonellosis, [7] [6] including human bartonellosis. Bartonella are the bacteria associated with so-called "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." [8] All current Bartonella spp. identified in canines are human pathogens. [9]
Bartonella infections are remarkable in the wide range of symptoms an infection can produce: the time course (acute or chronic) as well as the underlying pathology are highly variable.[10]
| 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 | 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 and Neuroretinitis | Worldwide |
| B. koehlerae | Incidental | Domestic cat | ||
| B. vinsonii | Incidental | Mouse, Dog, Domestic Cat | ||
| B. washoensis | Incidental | Squirrel | Myocarditis | |
| B. rochalimae | Incidental | Unknown | Carrion's disease-like symptoms | |
| References:[11][12][13] | ||||
Treatment is dependent on which 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.[10] 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.[10]
Homeless IV 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,[14] to 33% in Baltimore, Maryland,[15] 46% in New York,[16] and in Sweden 39%.[17]