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Polyagglutinable Pseudomonas aeruginosa from cystic fibrosis patients. A survey
1Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark.
Abstract:
Chronic Pseudomonas aeruginosa lung infection is responsible for most of the mortallity and morbility observed in cystic fibrosis patients. During the course of the disease, the bacteria change from being O-serogroup typable (monoagglutinable), non-mucoid, resistant to normal human serum and motile, to become O-serogroup non-typable (polyagglutinable), serum-sensitive and non-motile. In spite of high levels of antibodies produced by the patient, and intensive antibiotic therapy it is not possible to eradiate the polyagglutinable bacteria from the lungs of the patients. The bacteria will reappear and it is not fully understood if it is the same strain which reappears, or it is a super-infection with a new strain which takes place. A reliable and stable typing method is needed to clarify this question. In the present study, the conventional typing methods, such as serotyping, phage typing and pyocin typing were compared with the newer DNA typing methods, such as, restriction fragment length polymorphism (RFLP) in combination with pulsed field gel electrophoresis (PFGE) and typing with a specific DNA probe. Typability, reproducibility and discriminatory power using the different typing methods were investigated. The conventional typing methods have proved to be adequate when typing P. aeruginosa isolates from non cystic fibrosis sources, but because the majority of cystic fibrosis P. aeruginosa isolates are polyagglutinable or non typable, serotyping is not useful. Phage typing also lacks discriminatory power as it lumps up to 40% of the isolates in the same phage group. Pyocin typing has the disadvantage of low reproducibility. Most of the conventional typing methods are based on receptors on the bacterial surface, which on exposure to the environmental conditions in the lung, are likely to provoke phenotypic changes of the bacteria. The obvious advantage of the newer DNA typing methods is that these methods are based on internal properties of the bacteria, as part of the bacterial genome is investigated. The present study has revealed that for the time being, restriction fragment length polymorphism (RFLP) and pulsed field gel electrophoresis (PFGE) in combination with phage typing is the best method of typing P. aeruginosa isolates from cystic fibrosis patients for epidemiological purposes.
Insights
Identifying Pseudomonas aeruginosa strains in cystic fibrosis patients is crucial. DNA-based methods like RFLP and PFGE offer superior accuracy over traditional typing for tracking infections and understanding recurrence.
Area of Science:
- Clinical microbiology and infectious diseases.
- Molecular epidemiology of bacterial infections.
Background:
- Chronic Pseudomonas aeruginosa lung infections are a major cause of morbidity and mortality in cystic fibrosis (CF) patients.
- P. aeruginosa undergoes significant phenotypic changes during CF lung infections, complicating traditional strain typing.
- Distinguishing between relapse of the same strain and reinfection with a new strain is critical for patient management.
Purpose of the Study:
- To compare the efficacy of conventional bacterial typing methods with newer DNA-based typing techniques for P. aeruginosa isolates from CF patients.
- To identify the most reliable and stable typing method for epidemiological surveillance of P. aeruginosa in CF lung infections.
Main Methods:
- Conventional methods evaluated: serotyping, phage typing, and pyocin typing.
- DNA-based methods evaluated: restriction fragment length polymorphism (RFLP) with pulsed field gel electrophoresis (PFGE), and DNA probe typing.
- Typability, reproducibility, and discriminatory power were assessed for each method.
Main Results:
- Conventional methods showed limitations: serotyping was ineffective due to polyagglutinability, phage typing lacked discriminatory power, and pyocin typing had low reproducibility.
- DNA-based methods, particularly RFLP combined with PFGE, demonstrated higher typability and reproducibility.
- Phenotypic changes in P. aeruginosa within the CF lung environment render surface-receptor-based typing methods unreliable.
Conclusions:
- DNA typing methods, based on stable genomic features, are superior for typing P. aeruginosa in CF patients.
- Restriction fragment length polymorphism (RFLP) and pulsed field gel electrophoresis (PFGE), especially when combined with phage typing, represent the current gold standard for epidemiological typing of P. aeruginosa in CF.
- Accurate strain typing is essential for understanding the epidemiology and management of chronic P. aeruginosa infections in cystic fibrosis.