We propose an optimized protocol for an extensive population analysis of Burkholderia cepacia and Burkholderia contaminans. Seven new polymorphisms were added to the recently proposed SNaPBcen assay, and a total of 18 markers ensured the clear identification and distinction of B. cepacia and B. contaminans isolates and high genotypic discrimination (Simpson index of 0.94) compared to those for multilocus sequence typing.
The Burkholderia cepacia complex (Bcc) is a very heterogeneous group of 20 bacterial species capable of adapting to an innumerable range of environments (1). The Bcc has emerged as an important opportunistic human pathogen mainly affecting those with serious underlying conditions such as cystic fibrosis (CF) and chronic granulomatous disease (2, 3). A major problem concerning Bcc infections is related to their intrinsic resistance to the antibiotics and biocides most frequently employed clinically, and combined therapy is often needed to treat such infections (4-6). Bcc identification can be challenging even with selective culture media (7,8), a large panel of biochemical tests in routine diagnosis (9), and automated identification systems (e.g., Vitek 2) (10). The recA gene sequence analysis currently offers better species discrimination within the Bcc (11). Multilocus sequence typing (MLST) has also been shown to be excellent for both species identification and strain differentiation (12), but its applicability is limited due to its high cost and time-consuming procedure. An alternative methodology, the SNaPBcen assay, which facilitates large-scale analysis of bacterial isolates, had been proposed for the identification and genotyping of B. cenocepacia (13).In 2009, the novel species B. contaminans and B. lata were proposed for a divergent group formerly classified as B. cepacia recA restriction fragment length polymorphism (RFLP) type K (taxon K) (14). B. contaminans has been isolated worldwide from both environmental and clinical samples (15-21). B. contaminans has a low prevalence in CF patients worldwide, with remarkable exceptions registered in Argentina (21), Brazil (15, 22), Spain (23), and Portugal (17). The epidemiological surveillance of Bcc bacteria in respiratory infections at the major Portuguese CF center of Hospital de Santa Maria (HSM), in Lisbon, identified an exceptionally high representation of B. cepacia species isolates. This fact was attributed to contamination of saline solutions for nasal application (24). Recently, after reexamination of the B. cepacia clinical isolates from the Institute for Bioengineering and Biosciences, Instituto Superior Técnico (iBB/IST) collection, isolates of the recA RFLP type K, formerly classified as B. cepacia species (24, 25), and some additional isolates were classified as B. contaminans (17).The aim of this study was to develop a single nucleotide polymorphism (SNP)-based method for identification and genotyping of B. cepacia and B. contaminans, hereby designated the SNaPBceBcon assay. The methodology implemented allows the clear distinc...