Bartonella species are gram-negative bacteria previously classified as Rickettsiae. They are facultative intracellular organisms that typically live within red blood cells (RBCs) and endothelial cells. They cause several uncommon diseases (see table Some Bartonella Infections Some Bartonella Infections ):
Many people who are affected by the some of these infections are immunocompetent, but disseminated bartonellosis tends to occur in immunocompromised people.
Bartonella infection (bartonellosis) is usually acquired by humans via an insect vector.