Multiplex RT-PCR analysis of isolates carrying pVE46 for the sul1 gene, incorporating RT-PCR for the rpsL gene as a control for mRNA quality and quantity. Lane 1, Hyperladder I DNA marker (Bioline, London, United Kingdom); lanes 2 to 13, isolates L1 to L12, respectively; lane 14, postpassage 345-2RifC/pVE46; lane 15, negative control (no template).