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Phenotypic characterization of clonal and non-clonal Pseudomonas aeruginosa from the lungs of adults with cystic fibrosis.

Tingpej P, Smith L, Rose B, Zhu H, Conibear T, Al Nassafi K, Manos J, Elkins M, Bye P, Willcox M, Bell S, Wainwright C, Harbour C

Department of Infectious Diseases and Immunology, University of Sydney, Sydney, Australia; Institute for Eye Research, Sydney, Australia; School of Optometry and Vision Science, The University of New South Wales, Sydney, Australia; Department of Respiratory Medicine, Royal Prince Alfred Hospital, Sydney, Australia; Department of Medicine, University of Sydney, Sydney, Australia; Adult Cystic Fibrosis Centre, The Prince Charles Hospital, Brisbane, Australia; Department of Medicine, University of Queensland, Brisbane, Australia; Department of Respiratory Medicine, Royal Children's Hospital, Brisbane, Australia; Department of Paediatrics and Child Health, University of Queensland, Brisbane, Australia.

The emergence of virulent Pseudomonas aeruginosa clones is a threat to cystic fibrosis (CF) patients globally. Characterisation of clonal P. aeruginosa is critical to understanding their clinical impact and developing strategies to meet this problem. Two clonal strains (AES-1 and AES-2) are circulating within CF centres in eastern Australia. In this study phenotypic characteristics of 43 (14 AES-1, 5 AES-2 and 24 non-clonal) P. aeruginosa isolates were compared to gain insight into the properties of clonal strains. All 43 isolates produced bands of predicted size in PCRs for vfr, rhlI, rhlR, lasA, lasB, aprA, rhlAB, and exoS genes; 42 were positive for lasI and lasR and none had exoU. Thirty-seven (86%) isolates were positive in total protease assays; on zymography, 24 (56%) produced elastase/staphylolysin and 22 (51%) alkaline protease. Clonal were more likely than non-clonal isolates to be positive for total proteases (p=0.02), to show elastase and alkaline protease activity by zymography (p=0.04 and p=0.01 respectively) and elastase activity by the elastin-Congo-red assay (p=0.04). There were no other associations with genotype. Overall, increasing patient age was associated with decreasing elastase activity (p=0.03). Thirty-two (74%) isolates had at least one N-acylhomoserine lactone (AHL) by thin-layer chromatography. rhl-associated AHL detection was associated with production and level of total protease and elastase activity (all p<0.01). Thirty-three (77%) isolates were positive for ExoS by western blot, 35 (81%) produced rhamnolipids, and 34 (79%) showed chitinase activity. Findings suggest that protease activity during chronic infection may contribute to transmissibility or virulence of these clonal strains.

Published 29 March 2007 in J Clin Microbiol.
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