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Research Article

Detection of Legionella DNA by PCR of whole-blood samples in a mouse model

Aoki, S., Hirakata, Y., Miyazaki, Y., Izumikawa, K., Yanagihara, K., Tomono, K., Yamada, Y., Tashiro, T., Kohno, S., Kamihira, S.

Journal of Medical Microbiology 2003; 52(4):325 · https://doi.org/10.1099/jmm.0.04999-0

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Summary auto-generated

This study developed and evaluated a PCR-based detection system for Legionella DNA in whole-blood samples using a mouse model of Legionella pneumonia. Researchers designed primers targeting a 106 bp region of the 16S rRNA gene that could detect multiple clinically relevant Legionella species including L. pneumophila, L. micdadei, L. bozemanae, L. dumoffii, L. longbeachae, L. gormanii, and L. jordanis, with high sensitivity (20 femtograms extracted DNA) and specificity. In A/J mice infected intratracheally with L. pneumophila, blood PCR remained positive for up to 8 days post-infection, whereas bronchoalveolar lavage fluid (BALF) PCR became negative by day 4. Blood culture yielded bacteria only on days 1-2, while BALF culture recovered the pathogen through day 3. Legionella urinary antigen remained detectable from days 1-12. The findings suggest that whole-blood PCR offers a non-invasive, convenient diagnostic method for Legionella pneumonia that may be useful clinically, particularly when respiratory specimens are difficult to obtain. The authors note that further prospective studies in human patients are needed to confirm sensitivity, specificity, and clinical utility before clinical implementation.

Key findings

  • PCR targeting the 16S rRNA gene detected Legionella DNA from whole-blood samples with high sensitivity (20 fg) and specificity across seven Legionella species and multiple L. pneumophila serogroups.
  • Blood PCR remained positive longer (through day 8) compared to BALF PCR (through day 3) in the mouse infection model, suggesting blood may be a more persistent diagnostic specimen.
  • Whole-blood PCR offers a non-invasive alternative to respiratory sampling methods like bronchoalveolar lavage, which are difficult to perform in patients with non-productive cough.
  • Blood culture and blood PCR showed different temporal patterns, with culture positive only days 1-2 while PCR detected Legionella DNA through day 8, indicating superior sensitivity of PCR.
  • Prospective clinical studies are required to validate whole-blood PCR performance in human patients before this method can be adopted for routine diagnostic use.

This summary was generated automatically from the article PDF and is not part of the original publication. Refer to the PDF for the authoritative text.

Abstract

A detection system for Legionella DNA in blood samples based on the PCR was developed and evaluated in A/J mice with experimentally induced Legionella pneumonia. Primers were designed to amplify a 106 bp DNA fragment of the 16S rRNA gene specific to Legionella species. The PCR system could detect clinically relevant Legionella species including Legionella pneumophila, Legionella micdadei, Legionella bozemanae, Legionella dumoffii, Legionella longbeachae, Legionella gormanii and Legionella jordanis. The sensitivity of the PCR system was 20 fg extracted DNA. In the mouse model, the blood PCR was compared with results obtained by PCR on bronchoalveolar lavage fluid (BALF) samples, cultures of blood and BALF and detection of Legionella urinary antigen. Blood PCR was positive until 8 days after infection, while BALF PCR became negative on day 4. These results indicate that PCR using blood samples may be a useful, convenient and non-invasive method for the diagnosis of Legionella pneumonia.