Genotyping of Burkholderia mallei from an outbreak of glanders in Bahrain suggests multiple introduction events.

Holger C Scholz,Angela Witte,Enrico Georgi,Bobby Johnson,David M Wagner,Julia M Riehm,Shanti Jose,Ulrich Wernery,Michaela Projahn,Talima Pearson,Paul S Keim,Heidie Hornstra,Renate Wernery,Rahime Terzioglu,Joerg Kinne,Crystal M Hepp,Marina Joseph,Joseph M Vinetz

doi:10.1371/journal.pntd.0003195

Abstract

BackgroundGlanders, caused by the gram-negative bacterium Burkholderia mallei, is a highly infectious zoonotic disease of solipeds causing severe disease in animals and men. Although eradicated from many Western countries, it recently emerged in Asia, the Middle-East, Africa, and South America. Due to its rareness, little is known about outbreak dynamics of the disease and its epidemiology.Methodology/Principal FindingsWe investigated a recent outbreak of glanders in Bahrain by applying high resolution genotyping (multiple locus variable number of tandem repeats, MLVA) and comparative whole genome sequencing to B. mallei isolated from infected horses and a camel. These results were compared to samples obtained from an outbreak in the United Arab Emirates in 2004, and further placed into a broader phylogeographic context based on previously published B. mallei data. The samples from the outbreak in Bahrain separated into two distinct clusters, suggesting a complex epidemiological background and evidence for the involvement of multiple B. mallei strains. Additionally, the samples from Bahrain were more closely related to B. mallei isolated from horses in the United Arab Emirates in 2004 than other B. mallei which is suggestive of repeated importation to the region from similar geographic sources.Conclusion/SignificanceHigh-resolution genotyping and comparative whole genome analysis revealed the same phylogenetic patterns among our samples. The close relationship of the Dubai/UAE B. mallei populations to each other may be indicative of a similar geographic origin that has yet to be identified for the infecting strains. The recent emergence of glanders in combination with worldwide horse trading might pose a new risk for human infections.

Highlights

Glanders is a life-threatening, notifiable zoonotic disease which is fatal to both animals and humans. It is caused by the gramnegative bacterium Burkholderia mallei [1]
As a highly infectious agent that can be transmitted by aerosol, causing invasive fatal disease in combination with resistance to multiple antibiotics, B. mallei is listed as a category B bio-threat agent by the CDC
Using B. mallei-specific real-time PCR and high resolution MLVA typing, we showed recently that the strain from the camel was genetically closely related to B. mallei strain Dubai 7 that was isolated from a horse during the contained outbreak of glanders in a quarantine station in the United Arab Emirates in 2004 [8]

Summary

Introduction

Glanders is a life-threatening, notifiable zoonotic disease which is fatal to both animals and humans. Regions of endemicity still exist in Asia, the Middle-East, Africa, and South America where it infects solipeds and camels These areas provide reservoirs for re-introduction of glanders into countries previously listed as glanders-free. Using B. mallei-specific real-time PCR and high resolution MLVA typing, we showed recently that the strain from the camel was genetically closely related to B. mallei strain Dubai 7 that was isolated from a horse during the contained outbreak of glanders in a quarantine station in the United Arab Emirates in 2004 [8]. In this current study, we characterize various B. mallei isolates from both events (the 2004 UAE outbreak and the 2010–’11 Bahrain outbreak), using MLVA and next-generation whole genome sequencing. Our results provide evidence that the recent outbreak in Bahrain was caused by two different B. mallei strains, suggesting two independent introductions

Methods

Findings

Author Contributions