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International audience; Bartonella henselae, the agent of cat scratch disease (CSD), appears to be a common organism responsible for lymphadenitis in both adults and children. There is a very low isolation rate for B. henselae from lymph nodes of patients with CSD. Our objective was to evaluate B. henselae viability in a large series of lymph nodes from patients with CSD. From January to November 2016, we analyzed lymph node biopsy samples from patients diagnosed with CSD. We used reverse transcription-quantitative polymerase chain reaction (RT-qPCR) to detect B. henselae RNA, as well as cultures, histological analyses, and fluorescence in situ hybridization (FISH). We tested 87 lymph nodes positive for B. henselae DNA but only 8 (9%) presented with B. henselae RNA. We did not find a significant difference for the pap threshold cycle (C-T) values between RNA-positive and RNA-negative lymph nodes (p = 0.5). Cultures, histological analyses, and FISH were negative for all the tested samples. We provide evidence that B. henselae are not or are rarely viable in most cases in the lymph nodes of patients with CSD.

The aim of this study was to compare 16 S rRNA gene amplification and sequencing with a systematic real-time PCR assay screening strategy that includes all common known pathogens recovered from lymph node biopsy specimens. Lymph node biopsy samples sent to our laboratory from January 2007 to December 2008 were tested in the study. Lymph nodes were screened for the presence of any bacteria by PCR amplification and sequencing targeting the 16 S rRNA gene and also by a specific real-time PCR strategy that includes Bartonella henselae, mycobacteria, Francisella tularensis, and Tropheryma whipplei. By testing 491 lymph nodes, we found that the sensitivity of our specific real-time PCR assay strategy was significantly higher than 16 S rRNA PCR amplification and sequencing for the detection of Bartonella henselae (142 vs 98; p < 10(-4)), Francisella tularensis (16 vs 10, p < 10(-4)), and mycobacteria (8 versus 3, p < 10(-4)). None of the samples was positive for Tropheryma whipplei. Our study demonstrates the usefulness and specificity of a systematic real-time PCR strategy for molecular analysis of lymph node biopsy specimens and the higher sensitivity compared with standard 16 S rRNA gene amplification and sequencing.