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Updated: Jun 6, 2026
Visualization of Pseudomonas aeruginosa within the Sputum of Cystic Fibrosis Patients
Published on: July 16, 2020
Comparison of three molecular techniques for typing Pseudomonas aeruginosa isolates in sputum samples from patients
Timothy J Kidd1, Keith Grimwood, Kay A Ramsay
1Queensland Paediatric Infectious Diseases Laboratory, Department of Infectious Diseases, Royal Children's Hospital, Queensland Children's Medical Research Institute, The University of Queensland, Brisbane, QLD, Australia. Tim_Kidd@health.qld.gov.au
Abstract:
Monitoring the emergence and transmission of Pseudomonas aeruginosa strains among cystic fibrosis (CF) patients is important for infection control in CF centers internationally. A recently developed multilocus sequence typing (MLST) scheme is used for epidemiologic analyses of P. aeruginosa outbreaks; however, little is known about its suitability for isolates from CF patients compared with that of pulsed-field gel electrophoresis (PFGE) and enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR). As part of a prevalence study of P. aeruginosa strains in Australian CF clinics, we compared the discriminatory power and concordance of ERIC-PCR, PFGE, and MLST among 93 CF sputum and 11 control P. aeruginosa isolates. PFGE and MLST analyses were also performed on 30 paired isolates collected 85 to 354 days apart from 30 patients attending two CF centers separated by 3,600 kilometers in order to detect within-host evolution. Each of the three methods displayed high levels of concordance and discrimination; however, overall lower discrimination was seen with ERIC-PCR than with MLST and PFGE. Analysis of the 50 ERIC-PCR types yielded 54 PFGE types, which were related by ≤ 6 band differences, and 59 sequence types, which were classified into 7 BURST groups and 42 singletons. MLST also proved useful for detecting novel and known strains and for inferring relatedness among unique PFGE types. However, 47% of the paired isolates produced PFGE patterns that within 1 year differed by one to five bands, whereas with MLST all paired isolates remained identical. MLST thus represents a categorical analysis tool with resolving power similar to that of PFGE for typing P. aeruginosa. Its focus on highly conserved housekeeping genes is particularly suited for long-term clinical monitoring and detecting novel strains.
Insights
Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) effectively monitor Pseudomonas aeruginosa strains in cystic fibrosis patients. MLST is ideal for long-term tracking and identifying new strains due to its stability over time.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Pseudomonas aeruginosa infections are a major concern in cystic fibrosis (CF) care.
- Accurate strain typing is crucial for infection control and understanding transmission dynamics in CF centers.
- The utility of multilocus sequence typing (MLST) for CF isolates compared to established methods like pulsed-field gel electrophoresis (PFGE) and enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR) needed evaluation.
Purpose of the Study:
- To compare the discriminatory power and concordance of ERIC-PCR, PFGE, and MLST for typing Pseudomonas aeruginosa isolates from Australian CF patients.
- To assess the suitability of MLST and PFGE for detecting within-host evolution of P. aeruginosa strains over time.
- To evaluate MLST's potential for long-term clinical monitoring and novel strain detection.
Main Methods:
- Comparative analysis of ERIC-PCR, PFGE, and MLST on 93 CF sputum and 11 control P. aeruginosa isolates.
- Longitudinal analysis of 30 paired isolates from CF patients collected 85 to 354 days apart using PFGE and MLST.
- Assessment of discriminatory power, concordance, and stability of each typing method.
Main Results:
- All three methods (ERIC-PCR, PFGE, MLST) showed high concordance and discrimination, with ERIC-PCR exhibiting lower discrimination than MLST and PFGE.
- MLST identified 59 sequence types from 50 ERIC-PCR types and 54 PFGE types.
- While 47% of paired isolates showed PFGE pattern changes within a year, all paired isolates remained identical by MLST, highlighting MLST's stability for long-term monitoring.
Conclusions:
- MLST provides a robust and stable method for typing Pseudomonas aeruginosa, comparable in resolution to PFGE.
- MLST is particularly advantageous for long-term clinical surveillance of CF patients and for identifying novel strains due to its focus on conserved housekeeping genes.
- MLST offers a reliable tool for epidemiological analysis and infection control in international CF settings.
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