In a typical MLVA, a number of well-selected and characterised (in terms of mutation rate and diversity) loci are amplified by polymerase chain reaction (PCR), so that the size of each locus can be measured, usually by electrophoresis of the amplification products together with reference DNA fragments (a so-called DNA size marker). Different electrophoresis equipment can be used depending on the required size estimate accuracy, and the local laboratory set-up, from basic agarose gel electrophoresis up to the more sophisticated and high-throughput capillary electrophoresis devices.[1] From this size estimate, the number of repeat units at each locus can be deduced. The resulting information is a code which can be easily compared to reference databases once the assay has been harmonised and standardised.[2][3]
MLVA has become a major first line typing tool in a number of pathogens where such an harmonisation could be achieved, including Mycobacterium tuberculosis,[4]Bacillus anthracis,[5]Brucella.[6][7]