The Study
We collected 2,540 environmental samples, 370 (280 soil, 80 water, 10 environmental water tank scrapes) from Texas and 2,170 (1,650 soil, 520 water) from throughout Puerto Rico. From the collected samples, we detected B. thailandensis DNA in 10 complex broth samples, 4 from Texas and 6 from Puerto Rico (Appendix, https://wwwnc.cdc.gov/EID/article/29/3/22-1245-App1.pdf). Culturing[10] yielded B. thailandensis isolates from 5 samples, 1 from Texas and 4 from Puerto Rico. In addition, we isolated B. thailandensis from a soil sample collected in Mississippi in July 2022 during a melioidosis cluster investigation.[11] Further, in 2021, we identified B. thailandensis infection in a 4th case-patient in the United States (Oklahoma) (Table). The patient was suspected to have aspirated water after a motor vehicle rollover into water; he died because of multiple complications (Appendix).
We used whole-genome analysis of those 7 isolates (National Center for Biotechnology Information BioProject nos. PRJNA575701, PRJNA818328, PRJNA908850) to place them within a larger phylogeographic context, including other B. thailandensis isolates from the United States and other global locations (Table; Figure). Environmental B. thailandensis isolates from Texas and Mississippi grouped in the same clade with clinical isolates from Texas and Louisiana and 2 environmental isolates from Asia. The 2021 clinical isolate from Oklahoma was most closely related to the isolate from the 2003 clinical case in Texas. Environmental isolates from Texas and Mississippi differed by more (4,639 single-nucleotide polymorphisms [SNPs]) than environmental isolates from Thailand and Australia (2,671 SNPs); B. pseudomallei isolates found in Australia and Asia are more diverse than isolates in the Americas.[10] We observed little diversity among the 4 B. thailandensis isolates from Puerto Rico; total diversity was 62 SNPs, and distance between any 2 isolates was 28–36 SNPs.
Figure.
Wholegenome maximum-likelihood phylogeny of global isolates in study of Burkholderia thailandensis from the environment in the United States (Table). Tree was constructed with 1,000 bootstrap replicates and rooted with B. pseudomallei. Bold indicates B. thailandensis genomes generated from isolates collected in this study; other B. thailandensis from the Western Hemisphere have epidemiologic information underlined. Scale bar indicates 3,000 SNPs.
Among the isolates identified in our study, in silico multilocus sequence type analysis (https://pubmlst.org/organisms/burkholderia-pseudomallei) revealed novel ace allele 106 in the 4 isolates from Puerto Rico and the clinical isolate from Oklahoma, assigning all 5 to novel sequence type (ST) 1772. Novel gltB allele 175 was identified in the isolate from Texas, which was assigned to novel ST1785. The isolate from Mississippi, which had a unique combination of alleles, was assigned to novel ST2019.
Emerging Infectious Diseases. 2023;29(3):618-621. © 2023 Centers for Disease Control and Prevention (CDC)
