Bartonella

# Overview
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. 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. In June 2007, a new species under the genus, called Bartonella rochalimae, was discovered. This is the sixth species known to infect humans, and the ninth species and subspecies, overall, known to infect humans.
Members of the genus Bartonella are alpha 2 subgroup Proteobacteria. The genus comprises:

# Historical Perspective
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 after Alberto Leonardo Barton Thompson, a Peruvian scientist born in Argentina.
Bartonella was found to be a tick borne pathogen in 1999.
In 2001 doctors treating Lyme disease first reported that their patients were co-infected with Bartonella.  Multiple reports of this finding seem to indicate that Bartonella is not only a tick borne but a tick-transmitted pathogen; however, actual transmission via this route has not yet been proven.

# Pathophysiology

## Infection cycle
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 in the blood stream where they infect erythrocytes. The bacteria then invade and replicate within a phagosomal membrane inside the erythrocytes. Inside the erythrocytes, 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.
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.

## Medical Treatment
- Bartonella
- 1. Bartonella quintana
- 1.1 Acute or chronic infections without endocarditis
- Preferred regimen: Doxycycline 200 mg PO qd or 100 mg bid for 4 weeks AND Gentamicin 3 mg/kg IV qd for the first 2 weeks
- 1.2 Endocarditis
- Preferred regimen: Gentamicin 3 mg/kg/day IV q8h for 14 days AND Ceftriaxone 2 g IV q24h for 6 weeks  Doxycycline 100 mg PO bid for 6 weeks
- 2. Bartonella elizabethae
- 2.1 Endocarditis
- Preferred regimen: Gentamicin 3 mg/kg/day IV q8h for 14 days AND  Ceftriaxone 2 g IV q24h for 6 weeks  Doxycycline 100 mg PO bid for 6 weeks
- 3. Bartonella bacilliformis
- 3.1 Oroya fever
- Preferred regimen: Ciprofloxacin 500 mg PO bid for 14 days
- Note: If severe disease, add Ceftriaxone 1 g IV qd for 14 days
- 3.2 Verruga peruana
- Preferred regimen: Azithromycin 500 mg PO qd for 7 days
- Alternative regimen (1): Rifampin 600 mg PO qd for 14-21 days
- Alternative regimen (2): Ciprofloxacin 500 mg bid for 7-10 days
- 4. Bartonella henselae
- 4.1 Cat scratch disease
- No treatment recommended for typical cat scratch disease, consider treatment if there is an extensive lymphadenopathy
- 4.1.1 If extensive lymphadenopathy
- Preferred regimen (1) (pediatrics): Azithromycin 500 mg PO on day 1 THEN 250 mg PO qd on days 2 to 5
- Preferred regimen (2) (adults): Azithromycin 1 g PO at day 1 THEN 500 mg PO for 4 days
- 4.2 Endocarditis
- Preferred regimen: Gentamicin 3 mg/kg/day IV q8h for 14 days AND  Ceftriaxone 2 g/day IV for 6weeks  Doxycycline 100 mg PO bid for 6 weeks
- 4.3 Retinitis
- Preferred regimen: Doxycycline 100 mg bid AND  Rifampin 300 mg bid PO for 4-6 weeks
- 4.4 Bacillary angiomatosis
- Preferred regimen (1): Erythromycin 500 mg PO qid for 2 months at least
- Preferred regimen (2): Doxycycline 100 mg PO bid for 2 months at least
- 4.5 Bacillary Pelliosis
- Preferred regimen (1): Erythromycin 500 mg PO qid  for 4 months at least
- Preferred regimen (2): Doxycycline 100 mg PO bid for 4 months at least