Phenotypic differences among clinically isolated mucoid Pseudomonas aeruginosa strains

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Biochemistry

Background:

• Mucoid strains of Pseudomonas aeruginosa are significant pathogens in cystic fibrosis and urinary tract infections.
• The mucoid phenotype is associated with alginate production, a key virulence factor.
• Understanding the variability of mucoid P. aeruginosa is crucial for effective treatment strategies.

Purpose of the Study:

• To investigate phenotypic differences among mucoid Pseudomonas aeruginosa strains from cystic fibrosis (CF) and urinary tract infections (UTIs).
• To examine the relationship between alginate polysaccharide structure, phenotype stability, and medium-dependent expression.
• To identify common properties related to host colonization independent of observed phenotypic variations.

Main Methods:

• Isolation and characterization of mucoid P. aeruginosa strains from CF patients and UTI patients.
• Analysis of alginate composition (D-mannuronosyl/L-guluronosyl ratios and acetyl content).
• Assessment of mucoid phenotype stability and reversion frequency.
• Evaluation of mucoid phenotype expression across six different culture media.

Main Results:

• Significant variation in alginate structure (uronic acid ratios and acetylation) was observed among the 19 strains.
• Mucoid phenotype stability differed, with CF isolates showing both stable and unstable phenotypes, while UTI isolates were consistently unstable.
• Medium-dependent expression of the mucoid phenotype varied considerably, particularly for CF-associated strains.
• No clear correlation was found between polysaccharide structure, phenotype stability, and medium-dependent expression.

Conclusions:

• Mucoid P. aeruginosa strains exhibit substantial phenotypic heterogeneity in alginate production and stability.
• These variations are not directly correlated with the composition or expression of alginate.
• The common property enabling host colonization by mucoid P. aeruginosa likely resides in factors other than polysaccharide characteristics or their expression.