title: Two stable variants of Burkholderia pseudomallei strain MSHR5848 express broadly divergent in vitro phenotypes associated with their virulence differences.
abstract: Burkholderia pseudomallei (Bp), the agent of melioidosis, causes disease ranging from acute and rapidly fatal to protracted and chronic. Bp is highly infectious by aerosol, can cause severe disease with nonspecific symptoms, and is naturally resistant to multiple antibiotics. However, no vaccine exists. Unlike many Bp strains, which exhibit random variability in traits such as colony morphology, Bp strain MSHR5848 exhibited two distinct and relatively stable colony morphologies on sheep blood agar plates: a smooth, glossy, pale yellow colony and a flat, rough, white colony. Passage of the two variants, designated "Smooth" and "Rough", under standard laboratory conditions produced cultures composed of > 99.9% of the single corresponding type; however, both could switch to the other type at different frequencies when incubated in certain nutritionally stringent or stressful growth conditions. These MSHR5848 derivatives were extensively characterized to identify variant-associated differences. Microscopic and colony morphology differences on six differential media were observed and only the Rough variant metabolized sugars in selective agar. Antimicrobial susceptibilities and lipopolysaccharide (LPS) features were characterized and phenotype microarray profiles revealed distinct metabolic and susceptibility disparities between the variants. Results using the phenotype microarray system narrowed the 1,920 substrates to a subset which differentiated the two variants. Smooth grew more rapidly in vitro than Rough, yet the latter exhibited a nearly 10-fold lower lethal dose for mice than Smooth. Finally, the Smooth variant was phagocytosed and replicated to a greater extent and was more cytotoxic than Rough in macrophages. In contrast, multiple locus sequence type (MLST) analysis, ribotyping, and whole genome sequence analysis demonstrated the variants' genetic conservation; only a single consistent genetic difference between the two was identified for further study. These distinct differences shown by two variants of a Bp strain will be leveraged to better understand the mechanism of Bp phenotypic variability and to possibly identify in vitro markers of infection.
authors.affiliation: Diagnostic Systems Division, USAMRIID, Frederick, Maryland, United States of America.
authors.forename: A A
authors.initials: AA
authors.lastname: Shea
authors.affiliation: Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, Maryland, United States of America.
authors.forename: R C
authors.initials: RC
authors.lastname: Bernhards
authors.affiliation: Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, Maryland, United States of America.
authors.forename: C K
authors.initials: CK
authors.lastname: Cote
authors.affiliation: Diagnostic Systems Division, USAMRIID, Frederick, Maryland, United States of America.
authors.forename: C J
authors.initials: CJ
authors.lastname: Chase
authors.affiliation: Diagnostic Systems Division, USAMRIID, Frederick, Maryland, United States of America.
authors.forename: J W
authors.initials: JW
authors.lastname: Koehler
authors.affiliation: Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, Maryland, United States of America.
authors.forename: C P
authors.initials: CP
authors.lastname: Klimko
authors.affiliation: Center for Genome Sciences, USAMRIID, Frederick, Maryland, United States of America.
authors.forename: J T
authors.initials: JT
authors.lastname: Ladner
authors.affiliation: Diagnostic Systems Division, USAMRIID, Frederick, Maryland, United States of America.
authors.forename: D A
authors.initials: DA
authors.lastname: Rozak
authors.affiliation: Diagnostic Systems Division, USAMRIID, Frederick, Maryland, United States of America.
authors.forename: M J
authors.initials: MJ
authors.lastname: Wolcott
authors.affiliation: Biostatistical Services Division, USAMRIID, Frederick, Maryland, United States of America.
authors.forename: D P
authors.initials: DP
authors.lastname: Fetterer
authors.affiliation: Biostatistical Services Division, USAMRIID, Frederick, Maryland, United States of America.
authors.forename: S J
authors.initials: SJ
authors.lastname: Kern
authors.affiliation: Center for Genome Sciences, USAMRIID, Frederick, Maryland, United States of America.
authors.forename: G I
authors.initials: GI
authors.lastname: Koroleva
authors.affiliation: Center for Genome Sciences, USAMRIID, Frederick, Maryland, United States of America.
authors.forename: S P
authors.initials: SP
authors.lastname: Lovett
authors.affiliation: Center for Genome Sciences, USAMRIID, Frederick, Maryland, United States of America.
authors.forename: G F
authors.initials: GF
authors.lastname: Palacios
authors.affiliation: Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, Maryland, United States of America.
authors.forename: R G
authors.initials: RG
authors.lastname: Toothman
authors.affiliation: Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, Maryland, United States of America.
authors.forename: J A
authors.initials: JA
authors.lastname: Bozue
authors.affiliation: Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, Maryland, United States of America.
authors.forename: P L
authors.initials: PL
authors.lastname: Worsham
authors.affiliation: Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, Maryland, United States of America.
authors.forename: S L
authors.initials: SL
authors.lastname: Welkos
mesh_terms: D000818:Animals; D016957:Burkholderia pseudomallei / Q000235:genetics* / Q000472:pathogenicity; D002460:Cell Line; D024881:Drug Resistance, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D010641:Phenotype; D011110:Polymorphism, Genetic; D014774:Virulence / Q000235:genetics