Burkholderia pseudomallei, the causative agent of melioidosis, is rare but ecologically established and widely dispersed in the environment in Puerto Rico

Author summary The objective of this study was to examine the distribution and abundance of Burkholderia pseudomallei in the environment in Puerto Rico. B. pseudomallei is a microbe that lives in soil and causes the disease melioidosis. We conducted sampling around Puerto Rico to survey for the presence of B. pseudomallei in the environment. Of the 600 environmental samples collected, we isolated live B. pseudomallei from just two soil samples collected from the same site, which was in a region of the island where B. pseudomallei had never been previously reported. These results suggest B. pseudomallei is widely dispersed but rare in the environment in Puerto Rico. B. pseudomallei isolates from Puerto Rico are most closely related to other strains from the Caribbean. Caribbean strains are inside a larger group that contained all analyzed isolates from Central/South America, suggesting that B. pseudomallei populations in the Caribbean may have been introduced from Central or South America. Background Burkholderia pseudomallei is a soil-dwelling bacterium and the causative agent of melioidosis. The global burden and distribution of melioidosis is poorly understood, including in the Caribbean. B. pseudomallei was previously isolated from humans and soil in eastern Puerto Rico but the abundance and distribution of B. pseudomallei in Puerto Rico as a whole has not been thoroughly investigated. Methodology/Principal findings We collected 600 environmental samples (500 soil and 100 water) from 60 sites around Puerto Rico. We identified B. pseudomallei by isolating it via culturing and/or using PCR to detect its DNA within complex DNA extracts. Only three adjacent soil samples from one site were positive for B. pseudomallei with PCR; we obtained 55 isolates from two of these samples. The 55 B. pseudomallei isolates exhibited fine-scale variation in the core genome and contained four novel genomic islands. Phylogenetic analyses grouped Puerto Rico B. pseudomallei isolates into a monophyletic clade containing other Caribbean isolates, which was nested inside a larger clade containing all isolates from Central/South America. Other Burkholderia species were commonly observed in Puerto Rico; we cultured 129 isolates from multiple soil and water samples collected at numerous sites around Puerto Rico, including representatives of B. anthina, B. cenocepacia, B. cepacia, B. contaminans, B. glumae, B. seminalis, B. stagnalis, B. ubonensis, and several unidentified novel Burkholderia spp.