title: Nonrandom distribution of Burkholderia pseudomallei clones in relation to geographical location and virulence.
abstract: Burkholderia pseudomallei is a soil-dwelling saprophyte and the causative agent of melioidosis, a life-threatening human infection. Most cases are reported from northeast Thailand and northern Australia. Using multilocus sequence typing (MLST), we have compared (i) soil and invasive isolates from northeast Thailand and (ii) invasive isolates from Thailand and Australia. A total of 266 Thai B. pseudomallei isolates were characterized (83 soil and 183 invasive). These corresponded to 123 sequence types (STs), the most abundant being ST70 (n=21), ST167 (n=15), ST54 (n=12), and ST58 (n=11). Two clusters of related STs (clonal complexes) were identified; the larger clonal complex (CC48) did not conform to a simple pattern of radial expansion from an assumed ancestor, while a second (CC70) corresponded to a simple radial expansion from ST70. Despite the large number of STs, overall nucleotide diversity was low. Of the Thai isolates, those isolated from patients with melioidosis were overrepresented in the 10 largest clones (P<0.0001). There was a significant difference in the classification index between environmental and disease isolates (P<0.001), confirming that genotypes were not distributed randomly between the two samples. MLST profiles for 158 isolates from Australia (mainly disease associated) contained a number of STs (96) similar to that seen with the Thai invasive isolates, but no ST was found in both populations. There were also differences in diversity and allele frequency distribution between the two populations. This analysis reveals strong genetic differentiation on the basis of geographical isolation and a significant differentiation on the basis of virulence potential.
authors.affiliation: Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok 10400, Thailand, and Churchill Hospital, Oxford, UK.
authors.forename: Mongkol
authors.initials: M
authors.lastname: Vesaratchavest
authors.forename: Sarinna
authors.initials: S
authors.lastname: Tumapa
authors.forename: Nicholas P J
authors.initials: NP
authors.lastname: Day
authors.forename: Vanaporn
authors.initials: V
authors.lastname: Wuthiekanun
authors.forename: Wirongrong
authors.initials: W
authors.lastname: Chierakul
authors.forename: Matthew T G
authors.initials: MT
authors.lastname: Holden
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: White
authors.forename: Bart J
authors.initials: BJ
authors.lastname: Currie
authors.forename: Brian G
authors.initials: BG
authors.lastname: Spratt
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Feil
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Peacock
mesh_terms: D001315:Australia / Q000453:epidemiology; D015373:Bacterial Typing Techniques; D016957:Burkholderia pseudomallei / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005843:Geography; D006801:Humans; D008554:Melioidosis / Q000453:epidemiology / Q000382:microbiology*; D017720:Molecular Epidemiology; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D012988:Soil Microbiology; D013785:Thailand / Q000453:epidemiology; D014774:Virulence / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial