This pathogen may have been unidentified until now because of its slow growth, broad susceptibility to antimicrobial agents, and possible requirement of blood-cell lysis for recovery in culture. It should be sought as a cause of unexplained fever, especially in persons with defective cell-mediated immunity.

Nine strains of Rochalimaea spp. that were isolated from patients over a period of 4.5 years were characterized for their enzyme activities, cellular fatty acid compositions, and DNA interrelatedness among Rochalimaea spp., Bartonella bacilhformis, and Afipiafelis (cat scratch disease bacillus). All except one isolate, which was Rochalimaea quintana, were determined to belong to a newly proposed species, Rochalimaea henselae sp. nov. After recovery from clinical material, colonies required 5 to 15 days of incubation to become apparent. Cells were small, gram-negative, curved bacilli and displayed twitching motility. Enzyme specificities for amino acid and carbohydrate substrates showed that R. henselae could be distinguished from Rochalimaea vinsonii by L-arginyl-L-arginine and L-lysyl-L-alanine peptidases, but not all strains could be distinguished from R. quintana on the basis of peptidases or carbohydrate utilization. R. henselae also closely resembled R. quintana in cellular fatty acid composition, with both consisting mainly of C18:1, C18:0, and C16:0 fatty acids. However, the strains ofR. henselae all contained C18.0 in amounts averaging .22%, in contrast to R. quintana, which contained this cellular fatty acid in amounts averaging 16 and 18%. DNA hybridization confirmed the identification of one clinical isolate as R. quintana and showed a close interrelatedness (92 to 100%) among the other strains. Under optimal conditions for DNA reassociation, R. henselae showed approximately 70% relatedness to R. quintana and approximately 60% relatedness to R. vinsonii. Relatedness with DNA from B. bacilliformis was 43%. R. henselae was unrelated to A. felis. R. henselae is the proposed species of a newly recognized member of the family Rickettsiaceae, which is a pathogen that may be encountered in immunocompromised or immunocompetent patients. Prolonged fever with bacteremia or vascular proliferative lesions are clinical manifestations of the agent.

No abstract

Two previously healthy, immunocompetent men had persistent Rochalimaea henselae bacteremia with clinical relapses after courses of antibiotics to which the isolates were ultimately demonstrated susceptible in vitro. Both had sustained tick bites prior to their illnesses, thus demonstrating an association not previously identified, although suspected. The first patient had relapsing fever, constitutional symptoms, and an episode of aseptic meningitis despite therapy with amoxicillin, then with doxycycline, and then with ceftriaxone. Thereafter, he spontaneously became asymptomatic during a span of 2 months of persistent bacteremia. Finally, after 2 weeks of therapy with ceftriaxone plus gentamicin, followed by 4 weeks of therapy with oral ciprofloxacin, his bacteremia was cured. The second man had relapsing fever and constitutional symptoms after courses of tetracycline, then of chloramphenicol, and then of doxycycline. He became permanently asymptomatic after serial 2-week courses of chloramphenicol and erythromycin. The greater efficacy of lysis-centrifugation blood cultures in the recovery of R. henselae was noted.