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Analysis of quorum sensing-deficient clinical isolates of Pseudomonas aeruginosa

J Andy Schaber1, Nancy L Carty1, Naomi A McDonald1

  • 1Departments of Microbiology and Immunology,1 and Surgery,2 Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.

Journal of Medical Microbiology
|August 18, 2004
PubMed

Insights

Naturally occurring Pseudomonas aeruginosa strains deficient in quorum sensing (QS) can still cause human infections. These QS-deficient bacteria may possess other factors enabling them to establish infections despite lacking key virulence determinants.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Bacterial Pathogenesis

Background:

  • Pseudomonas aeruginosa is a versatile pathogen causing diverse infections.
  • Quorum sensing (QS) regulates virulence factors in P. aeruginosa, and QS mutants show reduced virulence in animal models.
  • The role of QS deficiency in human infections by P. aeruginosa is not fully understood.

Purpose of the Study:

  • To investigate if QS-deficient P. aeruginosa strains can establish human infections.
  • To characterize the virulence factors and genetic makeup of naturally occurring QS-deficient clinical isolates.

Main Methods:

  • Screening 200 clinical P. aeruginosa isolates for QS deficiency.
  • Assessing LasB, LasA, autoinducer production, and QS gene presence (lasI, lasR, rhlI, rhlR).
  • Evaluating other virulence factors: exotoxin A, pyocyanin, type III secretion system (TTSS) effectors, and biofilm formation.

Main Results:

  • Five QS-deficient strains were identified from urinary tract, respiratory tract, and wound infections.
  • These strains exhibited reduced or absent LasB, LasA, and autoinducer production.
  • Variable levels of exotoxin A, pyocyanin deficiency, and diverse TTSS effector profiles were observed; biofilm formation was weak to moderate.
  • One isolate (CI-1) lacked all tested virulence factors but still caused infection.

Conclusions:

  • Naturally occurring QS-deficient P. aeruginosa strains are present in clinical settings and can cause infections.
  • Virulence in some P. aeruginosa strains may involve factors beyond those regulated by QS.
  • Further research is needed to identify additional virulence determinants contributing to infection establishment by strains like CI-1.

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