First glanders cases detected in Nepal underscore the need for surveillance and border controls

Rapid confirmation of autochthonous origin in suspected cases of melioidosis from French overseas departments in the Caribbean and the Indian Ocean by PCR-high resolution melting (HRM) analysis

Burkholderia pseudomallei, a soil-borne bacterium that causes melioidosis, endemic in South and Southeast Asia and northern Australia, is now emerging in new regions. Since the 1990s, cases have been reported in French overseas departments, including Martinique and Guadeloupe in the Caribbean, and Reunion Island and Mayotte in the Indian Ocean, suggesting a local presence of the bacterium. Our phylogenetic analysis of 111 B. pseudomallei genomes isolated worldwide, including three strains from Martinique, revealed distinct geography-specific clades for Africa, the Americas, Asia and Australasia. Single nucleotide polymorphisms (SNP) that define clade branches in the phylogeny were identified; we selected those specific to three regions relevant to the French overseas departments: the Indian Ocean, the Americas and a unique subset specific to Martinique. Three SNP markers (one per region) were used to develop a PCR-high resolution melting tool to discriminate between local and imported strains in each region. Blind tests on B. pseudomallei strains from French patients, from overseas departments and mainland France, were used for validation. Our method accurately predicted the geographic origin of the patient as recorded from the patient travel history and/or from the multilocus sequence typing data. This rapid typing method, which allows timely identification of local cases and targeted public health interventions, is particularly valuable in the French overseas departments where melioidosis is emerging and regulatory constraints limit the handling of B. pseudomallei. Although initially tailored to specific regions, this tool can be adapted for use in other areas to support local epidemiological surveillance of melioidosis.

Development and validation of a chemiluminescent western blot assay for glanders (Burkholderia mallei) serodetection

Glanders, caused by Burkholderia mallei, is a zoonotic disease of equids. Serologic testing for glanders is required by disease-free countries before international movement of equids. The World Organisation for Animal Health Terrestrial Manual recommends the complement fixation test (CFT) for clearance of individual animals for movement, but the CFT is prone to false-positive results. A colorimetric western blot (WB) assay was developed and validated to resolve false-positive CFT results; however, that assay is relatively time-consuming, and the interpretation is subjective. We present here a procedurally similar chemiluminescent WB assay that performs comparably to the validated colorimetric WB assay and offers noticeable benefits of decreased time-to-result and greater ease of interpretation.

Sequence-based detection and typing procedures for Burkholderia mallei: Assessment and prospects

Although glanders has been eradicated in most of the developed world, the disease still persists in various countries such as Brazil, India, Pakistan, Bangladesh, Nepal, Iran, Bahrain, UAE and Turkey. It is one of the notifiable diseases listed by the World Organization for Animal Health. Occurrence of glanders imposes restriction on equestrian events and restricts equine movement, thus causing economic losses to equine industry. The genetic diversity and global distribution of the causing agent, Burkholderia (B.) mallei, have not been assessed in detail and are complicated by the high clonality of this organism. Among the identification and typing methods, PCR-based methods for distinguishing B. mallei from its close relative B. pseudomallei as well as genotyping using tandem repeat regions (MLVA) are established. The advent and continuous advancement of the sequencing techniques and the reconstruction of closed genomes enable the development of genome guided epidemiological tools. For achieving a higher genomic resolution, genotyping methods based on whole genome sequencing data can be employed, like genome-wide single nucleotide polymorphisms. One of the limitations in obtaining complete genomic sequences for further molecular characterization of B. mallei is its high GC content. In this review, we aim to provide an overview of the widely used detection and typing methods for B. mallei and illustrate gaps that still require development. The genomic features of Burkholderia, their high homology and clonality will be first described from a comparative genomics perspective. Then, the commonly used molecular detection (PCR systems) and typing systems (e.g., multilocus sequence typing, variable number of tandem repeat analysis) will be presented and put in perspective with recently developed genomic methods. Also, the increasing availability of B. mallei genomic sequences and evolution of the sequencing methods offers exciting prospects for further refinement of B. mallei typing, that could overcome the difficulties presently encountered with this particular bacterium.