Related Experiment Video
Updated: May 7, 2026
Visualization of Pseudomonas aeruginosa within the Sputum of Cystic Fibrosis Patients
Published on: July 16, 2020
Proposal of a quantitative PCR-based protocol for an optimal Pseudomonas aeruginosa detection in patients with cystic
Florence Le Gall1, Rozenn Le Berre, Sylvain Rosec
1EA 3882-Laboratoire de Biodiversité et d'Ecologie Microbienne (LUBEM), SFR 148 ScInBioS, Faculté de Médecine, Université de Brest, Brest F-29200, France. hery@univ-brest.fr.
Insights
Early detection of Pseudomonas aeruginosa in cystic fibrosis (CF) patients is crucial. A combined quantitative PCR (qPCR) protocol offers 100% sensitivity and specificity for identifying P. aeruginosa, improving CF patient management.
Area of Science:
- Microbiology
- Molecular Biology
- Pulmonology
Background:
- Cystic Fibrosis (CF) patients' lungs are highly susceptible to Pseudomonas aeruginosa infections, a key factor in poor patient outcomes.
- Early detection of P. aeruginosa acquisition is critical for managing CF patients.
- Quantitative PCR (qPCR) presents a promising method for earlier P. aeruginosa detection in CF patients.
Purpose of the Study:
- To establish an optimal molecular protocol for detecting P. aeruginosa in CF patients.
- To address the lack of a validated qPCR protocol for P. aeruginosa in CF sputum.
Main Methods:
- Comparison of two qPCR formats: one targeting the oprL gene and a multiplex PCR targeting gyrB and ecfX genes.
- In vitro testing on P. aeruginosa isolates and other gram-negative bacilli.
- Ex vivo validation on 46 CF sputum samples confirmed by culture.
Main Results:
- The oprL qPCR showed higher sensitivity (10 CFU/mL) compared to gyrB/ecfX qPCR (730 CFU/mL).
- The gyrB/ecfX qPCR demonstrated better specificity (90%) than oprL qPCR (73%).
- Ex vivo assays indicated qPCR detected 100 times more bacterial cells than traditional culture methods.
Conclusions:
- A combined qPCR protocol utilizing both oprL and gyrB/ecfX targets is proposed.
- This integrated protocol achieves 100% sensitivity and 100% specificity with a detection limit of 10 CFU/mL.
- The developed qPCR protocol is suitable for adaptation in future prospective studies for early P. aeruginosa detection in CF patients.
Background:
The lung of patients with cystic fibrosis (CF) is particularly sensitive to Pseudomonas aeruginosa. This bacterium plays an important role in the poor outcome of CF patients. During the disease progress, first acquisition of P. aeruginosa is the key-step in the management of CF patients. Quantitative PCR (qPCR) offers an opportunity to detect earlier the first acquisition of P. aeruginosa by CF patients. Given the lack of a validated protocol, our goal was to find an optimal molecular protocol for detection of P. aeruginosa in CF patients.
Methods:
We compared two formerly described qPCR formats in early detection of P. aeruginosa in CF sputum samples: a qPCR targeting oprL gene, and a multiplex PCR targeting gyrB and ecfX genes.
Results:
Tested in vitro on a large panel of P. aeruginosa isolates and others gram-negative bacilli, oprL qPCR exhibited a better sensitivity (threshold of 10 CFU/mL versus 730 CFU/mL), whereas the gyrB/ecfX qPCR exhibited a better specificity (90% versus 73%). These results were validated ex vivo on 46 CF sputum samples positive for P. aeruginosa in culture. Ex vivo assays revealed that qPCR detected 100 times more bacterial cells than culture-based method did.
Conclusion:
Based on these results, we proposed a reference molecular protocol combining the two qPCRs, which offers a sensitivity of 100% with a threshold of 10 CFU/mL and a specificity of 100%. This combined qPCR-based protocol can be adapted and used for other future prospective studies.
