Differential detection of Bartonella species and strains in cat scratch disease diagnostics by polymerase chain reaction amplification of 16S ribosomal RNA gene

Institute of Environmental Studies, School of Veterinary Medicine, Louisiana State University, Baton Rouge 70803, USA.

Cat scratch disease (CSD) has been difficult to diagnose in animals because of the protracted clinical course of infection and the quiescent phases when the microbial culprit lies dormant. The causative agent in CSD appears to be multiple species and strains of Bartonella. Using polymerase chain reaction (PCR) techniques for amplification of highly variable regions of the 16S ribosomal RNA (rRNA) gene sequence, a very sensitive species- and strain-specific assay for CSD-causing Bartonella species was developed. PCR primers were designed to specifically amplify the 16S rRNA gene of Bartonella species but not of other microbial pathogens. This initial PCR was multiplexed with a universal primer set, based on conserved sequence regions in the 16S rRNA gene, that provides a 162-bp fragment in all species tested. Subsequently, 3 distinct nested PCR primer sets enabled the individual amplification and specific detection of Bartonella henselae type 1, B. henselae type II, and B. clarridgeae. Thus, this 2-step PCR procedure enabled the sensitive detection and identification of these species and the B. henselae genotype by exploiting minor sequences differences. Verification of these results were demonstrated with both sequencing and ligase chain reaction techniques. The diagnostic usefulness of this CSD test has been demonstrated by the analysis of specimens from control and infected cats. The diagnosis was confirmed and the specific B. henselae strain was correctly identified in peripheral blood specimens obtained from control and strain-specific CSD-infected cats. Such an accurate and sensitive diagnostic tool for the detection and identification of CSD causative agents should be a useful for the medical, veterinary, and scientific communities.