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Journal of Clinical Microbiology, November 2004, p. 5229-5237, Vol. 42, No. 11
0095-1137/04/$08.00+0     DOI: 10.1128/JCM.42.11.5229-5237.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Type III Secretion Phenotypes of Pseudomonas aeruginosa Strains Change during Infection of Individuals with Cystic Fibrosis

Manu Jain,1 Daniel Ramirez,2 Roopa Seshadri,3,4 Joanne F. Cullina,1 Catherine A. Powers,5 Grant S. Schulert,2,{dagger} Maskit Bar-Meir,6 Christine L. Sullivan,4 Susanna A. McColley,5 and Alan R. Hauser1,2*

Department of Medicine,1 Department of Microbiology/Immunology,2 Departments of Pediatrics and Preventive Medicine, Northwestern University,3 Child Health Research Program, Children's Memorial Institute for Education and Research,4 Division of Pulmonary and Critical Care Medicine,5 Division of Infectious Diseases, Children's Memorial Hospital, Chicago, Illinois6

Received 18 March 2004/ Returned for modification 14 June 2004/ Accepted 30 July 2004

Pseudomonas aeruginosa is a frequent cause of respiratory exacerbations in individuals with cystic fibrosis. An important virulence determinant of this pathogen is its type III protein secretion system. In this study, the type III secretion properties of 435 P. aeruginosa respiratory isolates from 56 chronically infected individuals with cystic fibrosis were investigated. Although it had been previously reported that 75 to 90% of P. aeruginosa isolates from patients with hospital-acquired pneumonia secreted type III proteins, only 12% of isolates from cystic fibrosis patients did so, with nearly all of these isolates secreting ExoS and ExoT but not ExoU. Despite the low overall prevalence of type III protein-secreting isolates, at least one secreting isolate was cultured from one-third of cystic fibrosis patients. Interestingly, the fraction of cystic fibrosis patient isolates capable of secreting type III proteins decreased with duration of infection. Although 90% of isolates from the environment, the presumed reservoir for the majority of P. aeruginosa strains that infect patients with cystic fibrosis, secreted type III proteins, only 49% of isolates from newly infected children, 18% of isolates from chronically infected children, and 4% of isolates from chronically infected adults with cystic fibrosis secreted these proteins. Within individual patients, isolates of clonal origin differed in their secretion phenotypes, indicating that as strains persisted in cystic fibrosis patient airways, their type III protein secretion properties changed. Together, these findings indicate that following infection of cystic fibrosis patient airways, P. aeruginosa strains gradually change from a type III protein secretion-positive phenotype to a secretion-negative phenotype.


* Corresponding author. Mailing address: Northwestern University, 303 East Chicago Ave., Searle 6-495, Chicago, IL 60611. Phone: (312) 503-1044. Fax: (312) 503-1339. E-mail: ahauser{at}northwestern.edu.

{dagger} Present address: University of Iowa, Iowa City, Iowa.


Journal of Clinical Microbiology, November 2004, p. 5229-5237, Vol. 42, No. 11
0095-1137/04/$08.00+0     DOI: 10.1128/JCM.42.11.5229-5237.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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