The rapid increase in Pseudomonas (Burkholderia) cepacia infection in cystic fibrosis (CF) patients suggests epidemic transmission, but the degree of transmissibility remains controversial as conflicting conclusions have been drawn from studies at different CF centres. This report provides the first DNA sequence-based documentation of a divergent evolutionary lineage of P. cepacia associated with CF centre epidemics in North America (Toronto) and Europe (Edinburgh). The involved epidemic clone encoded and expressed novel cable (Cbl) pili that bind to CF mucin. The sequence of the cblA pilin subunit gene carried by the epidemic isolates proved to be invariant. Although it remains to be determined how many distinct, highly transmissible lineages exist, our results provide both a DNA sequence and chromosomal fingerprint that can be used to screen for one such particularly infectious, transatlantic clone.

Burkholderia cepacia is an important pathogen in cystic fibrosis (CF) and an infrequent cause of nosocomial infection in non-CF patients. This report describes a large hospital outbreak that appeared to involve both patient groups, a previously unrecognized phenomenon. Ribotype restriction fragment length polymorphism (RFLP) profiles and pulsed-field gel electrophoresis-resolved macrochromosomal RFLPs were analyzed, a ribotype-based phylogenic tree was constructed, and case-control and cohort studies were performed. A single dominant clone was found in both CF and non-CF groups. Phylogenic analysis suggests that it has evolved independently and that such highly transmissible strains can emerge rapidly and randomly. Acquisition risk in the CF patients was linked to hospitalization (odds ratio=5.47, P=.0158, confidence interval=1. 28-26.86) and was associated with significantly increased mortality rates. Infection control policies must now consider this threat of transmission between non-CF and CF patients.

One or more of five morphologically distinct classes of appendage pili were determined to be peritrichously expressed by Burkholderia (formerly Pseudomonas) cepacia isolated from disparate sources. B. cepacia-encoded cblA pilin gene hybridization-based analysis revealed that one associated class, cable (Cbl) adhesin type II B. cepacia pili, correlates with epidemically transmitted strains from a single cystic fibrosis (CF) center. When only phenotypic assays were available, correlations between the source and the pilus type were nonetheless observed: filamentous (Fil) type III B. cepacia pili correlated with CF-associated nonepidemic isolates, spine (Spn) type IV B. cepacia pili correlated with clinical (non-CF) isolates, and spike (Spk) type V B. cepacia pili correlated with environmental isolates. Further, Cbl, Fil, or Spk pili typically appear as an internal framework for constitutively coexpressed, peritrichously arranged dense mats of fine, curly mesh (Msh) type I B. cepacia pili. Constitutive coexpression of dense mats of Msh type I B. cepacia pili in association with a labyrinth of either Cbl, Fil, or Spk pili suggests possible cooperative pilus interactions mediating adhesion-based colonization in the differing environments from which the strains were isolated. Despite such correlations, phylogenetic analyses indicate that with the exception of the epidemically transmitted clusters of isolates, the remaining B. cepacia strains from the other three sources exhibited an equal degree of genetic relatedness independent of origin. As previously found for Escherichia coli, this discrepancy could be accounted for by selection-driven, in vivo horizontal transfer events between distantly related members of the species B. cepacia, leading to the genetic acquisition of environmentally appropriate adhesion-based colonization pilus operons.In a companion report (46), we describe the purification and immunolocalization of a 17-kDa major subunit pilin protein of a cystic fibrosis (CF)-associated Burkholderia (formerly Pseudomonas) cepacia isolate and reveal that it is peritrichously assembled into novel, giant cable-like appendage (Cbl) pilus fibers. Also described are the sequence of the encoding structural gene (cblA) and the deduced amino acid sequence of the encoded CblA major subunit pilin protein, and the observation that this protein is chromosomally encoded among B. cepacia isolates is made.While carrying out the above-mentioned study (46), we observed peritrichous coexpression of a second, morphologically distinct class of extremely fine, steel wool-like mesh (Msh) pilus fibers from all 14 B. cepacia isolates expressing Cbl pili. Because all of the involved isolates were obtained from patients at a particular CF center in Toronto, we expanded the survey, using high-resolution transmission electron microscopy to determine whether Cbl and Msh pili were likewise coexpressed under identical growth conditions by B. cepacia isolates from patients at five other CF centers in North America and Europe as well as by cli...