Bartonellosis - New and old

The number of species that comprise the family Bartonellaceae, genus Bartonella has recently increased from only one, Bartonella bacilliformis, to 14 species. At least five of these, B. bacilliformis, B. henselae, B. quintana, B. elizabethae and B. clarridgeae, have been associated with different diseases and syndromes in humans; the rapidly growing number of human pathogens has led several investigators to regard bartonellosis and other syndromes associated with the Bartonella species as important emerging infectious diseases.(4, 12, 38, 45) Recently published nucleotide sequences of the 16S RNA showed that Bartonella organisms belonged to the Alpha 2 subgroup of bacteria, Protobacterieae class, which also includes Rickettsia, Ehrlichia, Brucella, Afipia, and Agrobacterium tumifacieus(45); however, because of homology in the sequence of the 16S RNA between B. bacilliformis and the former Rochalimaea, as well as the recognition of DNA hybrids and similarities in the guanine and cytosine contents, Bartonella and the former Rochalimaea rickettsii are classified together in the family Bartonellaceae. The family includes four new species: henselae, quintana, elizabethae, and vinsonii.(18, 53) Since 1995, five Grahamella species (talpae, grahamii, taylori, peromyscii, and doshiae) have been classified as new Bartonella species because of similar molecular structure.(16) Also, another species, Bartonella clarridgeae, was described in 1995 and was found to be a human pathogen.(46) Bartonella organisms are widely dispersed in nature. Only B. bacilliformis and B. clarridgeae are flagellated species. Bartonella are fastidious bacteria that will grow in blood-enriched agar; however, it is considered to be a facultative intracellular pathogen.(63)