title: Burkholderia pseudomallei isolates from Sarawak, Malaysian Borneo, are predominantly susceptible to aminoglycosides and macrolides.
abstract: Melioidosis is a potentially fatal disease caused by the saprophytic bacterium Burkholderia pseudomallei. Resistance to gentamicin is generally a hallmark of B. pseudomallei, and gentamicin is a selective agent in media used for diagnosis of melioidosis. In this study, we determined the prevalence and mechanism of gentamicin susceptibility found in B. pseudomallei isolates from Sarawak, Malaysian Borneo. We performed multilocus sequence typing and antibiotic susceptibility testing on 44 B. pseudomallei clinical isolates from melioidosis patients in Sarawak district hospitals. Whole-genome sequencing was used to identify the mechanism of gentamicin susceptibility. A novel allelic-specific PCR was designed to differentiate gentamicin-sensitive isolates from wild-type B. pseudomallei. A reversion assay was performed to confirm the involvement of this mechanism in gentamicin susceptibility. A substantial proportion (86%) of B. pseudomallei clinical isolates in Sarawak, Malaysian Borneo, were found to be susceptible to the aminoglycoside gentamicin, a rare occurrence in other regions where B. pseudomallei is endemic. Gentamicin sensitivity was restricted to genetically related strains belonging to sequence type 881 or its single-locus variant, sequence type 997. Whole-genome sequencing identified a novel nonsynonymous mutation within amrB, encoding an essential component of the AmrAB-OprA multidrug efflux pump. We confirmed the role of this mutation in conferring aminoglycoside and macrolide sensitivity by reversion of this mutation to the wild-type sequence. Our study demonstrates that alternative B. pseudomallei selective media without gentamicin are needed for accurate melioidosis laboratory diagnosis in Sarawak. This finding may also have implications for environmental sampling of other locations to test for B. pseudomallei endemicity.
authors.affiliation: Global and Tropical Health Division, Menzies School of Health Research, Darwin, Northern Territory, Australia.
authors.forename: Yuwana
authors.initials: Y
authors.lastname: Podin
authors.forename: Derek S
authors.initials: DS
authors.lastname: Sarovich
authors.forename: Erin P
authors.initials: EP
authors.lastname: Price
authors.forename: Mirjam
authors.initials: M
authors.lastname: Kaestli
authors.forename: Mark
authors.initials: M
authors.lastname: Mayo
authors.forename: KingChing
authors.initials: K
authors.lastname: Hii
authors.forename: Hieung
authors.initials: H
authors.lastname: Ngian
authors.forename: SeeChang
authors.initials: S
authors.lastname: Wong
authors.forename: IngTien
authors.initials: I
authors.lastname: Wong
authors.forename: JinShyan
authors.initials: J
authors.lastname: Wong
authors.forename: Anand
authors.initials: A
authors.lastname: Mohan
authors.forename: MongHow
authors.initials: M
authors.lastname: Ooi
authors.forename: TemLom
authors.initials: T
authors.lastname: Fam
authors.forename: Jack
authors.initials: J
authors.lastname: Wong
authors.forename: Apichai
authors.initials: A
authors.lastname: Tuanyok
authors.forename: Paul
authors.initials: P
authors.lastname: Keim
authors.forename: Philip M
authors.initials: PM
authors.lastname: Giffard
authors.forename: Bart J
authors.initials: BJ
authors.lastname: Currie
mesh_terms: D000617:Aminoglycosides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016957:Burkholderia pseudomallei / Q000187:drug effects*; D005839:Gentamicins / Q000494:pharmacology; D018942:Macrolides / Q000494:pharmacology*; D008296:Malaysia; D008826:Microbial Sensitivity Tests
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D005839:Gentamicins; D018942:Macrolides