Significant differences in type IV pilin allele distribution among Pseudomonas aeruginosa isolates from cystic fibrosis (CF) versus non-CF patients

1 Centre for Infection and Biomaterials Research, Hospital for Sick Children Research Institute and Department of Surgery, University of Toronto, 7142A Elm Wing, 555 University Avenue, Toronto, ON, Canada M5G 1X8 2 Adult Cystic Fibrosis Clinic, St Michael's Hospital, Toronto, ON, Canada 3 Department of Microbiology, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada Correspondence Lori L. Burrows lori.burrows{at}sickkids.ca Type IV pili (TFP) are important colonization factors of the opportunistic pathogen Pseudomonas aeruginosa , involved in biofilm formation and attachment to host cells. This study undertook a comprehensive analysis of TFP alleles in more than 290 environmental, clinical, rectal and cystic fibrosis (CF) isolates of P. aeruginosa . Based on the results, a new system of nomenclature is proposed, in which P. aeruginosa TFP are divided into five distinct phylogenetic groups. Each pilin allele is stringently associated with characteristic, distinct accessory genes that allow the identification of the allele by specific PCR. The invariant association of the pilin and accessory genes implies horizontal transfer of the entire locus. Analysis of pilin allele distribution among isolates from various sources revealed a striking bias in the prevalence of isolates with group I pilin genes from CF compared with non-CF human sources ( P