Disproportionate distribution of Burkholderia cepacia complex species and transmissibility markers in cystic fibrosis

Several distinct species (genomovars) comprise bacteria previously identifi ed merely as Burkholderia cepacia. Understanding how these species, collect ively referred to as the B. cepacia complex, differ in their epidemiology a nd pathogenic potential in cystic fibrosis (CF) is important in efforts to refine management strategies. B. cepacia isolates recovered from 606 CF pat ients receiving care at 132 treatment centers in 105 cities in the United S tates were assessed to determine species within the B. cepacia complex and examined for the presence of putative transmissibility markers (B. cepacia epidemic strain marker [BCESM] and cable pilin subunit gene [cblA]). Fifty percent of patients were infected with B. cepacia complex genomovar III, 38 % with B. multivorans (formerly genomovar II), and 5% with B. vietnamiensis (formerly genomovar V); fewer than 5% of patients were infected with eithe r genomovar I, B. stabilis (formerly genomovar IV), genomovar VI, or genomo var VII. BCESM was found in 46% of genomovar III isolates and not in any ot her species. Only one isolate, from a patient infected with the ET12 epidem ic lineage, contained the complete cblA pilin subunit gene. Our data indica te a differential capacity for human infection among the phylogenetically c losely related species of the B. cepacia complex. The low frequency of BCES M and cblA suggests that they are not sufficient markers of B. cepacia viru lence or transmissibility.