Application of an 8-locus MLVA typing system on Burkholderia mallei isolates collected in Iran from 2012 to 2020, a fresh update

Burkholderia mallei remains actively plaguing soliped populations across the Middle and Far East despite the long years of ongoing test and slaughter schemes run by the region States. This includes Iran with occasional reports of glanders and rarely-occurred cases of human infections. The Multiple locus Variable Number of Tandem Repeat (VNTR) Analysis (MLVA) has proved very effective in resolving of Burkholderia mallei strains. Here, a molecular strain-typing system based on 8 variable-number tandem-repeat (VNTR) loci is reported. This strategy was laboratory-tested on a panel of 6 indigenous isolates representing the most recent outbreaks of glanders in Iran and a single Swedish strain of B. mallei. A further collection of 20 B. mallei and 2 B. pseudomallei reference strains genomes obtained from Pubmed databases were also included in the study to conduct in-situ assessment. The number of alleles detected ranged from 1 (Locus 41) to 10 (locus) with the Nei’s diversity index values ranged from 0.53 to 0.89. On the whole, the typing system designated 27 isolates into 25 genotypes and more specifically the 7 B mallei from Iran to 6 types. Authors believe by the time when the whole genome sequencing platforms have come economically available to the low-income laboratory settings in the developing world, the optimized versions of MLVA typing method such as the one described here deliver broad potential for epidemiological investigation of B. mallei and revelation of relationships between isolates at local, regional and worldwide scale.