Identification of Melioidosis Outbreak by Multilocus Variable Number Tandem Repeat Analysis

Bart J Currie,Asha Haslem,Mark Mayo,Talima Pearson,Heidie Hornstra,Paul Keim,Daniel Gal,Linda Ward,Brian G Spratt,Daniel Godoy,Benjamin Leadem

doi:10.3201/eid1502.081036

Abstract

Endemic melioidosis is caused by genetically diverse Burkholderia pseudomallei strains. However, clonal outbreaks (multiple cases caused by 1 strain) have occurred, such as from contaminated potable water. B. pseudomallei is designated a group B bioterrorism agent, which necessitates rapidly recognizing point-source outbreaks. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) can identify genetically related isolates, but results take several days to obtain. We developed a simplified 4-locus multilocus variable number tandem repeat analysis (MLVA-4) for rapid typing and compared results with PFGE and MLST for a large number of well-characterized B. pseudomallei isolates. MLVA-4 compared favorably with MLST and PFGE for the same isolates; it discriminated between 65 multilocus sequence types and showed relatedness between epidemiologically linked isolates from outbreak clusters and between isolates from individual patients. MLVA-4 can establish or refute that a clonal outbreak of melioidosis has occurred within 8 hours of receipt of bacterial strains.

Highlights

Endemic melioidosis is caused by genetically diverse Burkholderia pseudomallei strains
B. pseudomallei is classified as a group B bioterrorism agent by the US Centers for Disease Control and Prevention, and the implications of a possible deliberate release warrant the availability of a robust method to quickly ascertain if concomitant cases of melioidosis are caused by 1 bacterial strain
Relationships between sequence type (ST) seen on the multilocus sequence typing (MLST) dendrogram were generally not preserved with MLVA-4

Summary

Introduction

Endemic melioidosis is caused by genetically diverse Burkholderia pseudomallei strains. Pulsedfield gel electrophoresis (PFGE) and multilocus sequence typing (MLST) can identify genetically related isolates, but results take several days to obtain. We developed a simplified 4-locus multilocus variable number tandem repeat analysis (MLVA-4) for rapid typing and compared results with PFGE and MLST for a large number of well-characterized B. pseudomallei isolates. Because several days are required to perform the currently available molecular typing methods of ribotyping, multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE), the ability to rapidly distinguish endemic infection from a clonal outbreak has not been possible. B. pseudomallei is classified as a group B bioterrorism agent by the US Centers for Disease Control and Prevention, and the implications of a possible deliberate release warrant the availability of a robust method to quickly ascertain if concomitant cases of melioidosis are caused by 1 bacterial strain. We have compared MLVA results on a wide range of well-characterized B. pseudomallei isolates with those for MLST and PFGE

Methods

Results

Conclusion