Bartonella
Bartonella species are members of the alpha-2 subgroup of the class Alphaproteobacteria , within the Rhizobiales order. There are now more than 22 species or subspecies described, and DNA sequences from numerous other species or strains have been deposited in GenBank. Warthin-Starry silver stain is recommended for microscopic detection of Bartonella organisms in fixed tissue sections but is not highly specific and is insensitive, even with lymph node biopsy samples from cat scratch disease (CSD) patients. In contrast, even when isolation of the infecting species is not possible, PCR amplification of internal transcribed spacer (ITS) DNA directly from diagnostic samples and/or from enrichment cultures followed by nucleic acid sequencing is an invaluable tool for primary identification at the species, subspecies, and genotype levels. The first serologic test for CSD was an immunofluorescence antibody assay (IFA) based on B. henselae bacilli that were cocultivated with Vero cells to inhibit autoagglutination. Antimicrobial susceptibility testing can be performed by agar dilution methods using either blood or chocolate agar or by microdilution techniques using various media supplemented with blood. CSD typically does not respond to antibiotic therapy. Most investigators have observed no or minimal benefit with antibiotic treatment, whereas anecdotal reports indicate that ciprofloxacin, rifampin, and co-trimoxazole may be effective. Diagnosis of Bartonella infection in humans, especially for typical forms of CSD, is mainly based on serologic data, which is the most cost-effective approach.
