“…Notwithstanding the fact that genotypic drug susceptibility testing has a high sensitivity and specificity but is still unable to detect all the resistance, especially in strains with novel or unknown resistance mechanisms [ 40 , 41 ]. In this review, 49 isolates with confirmed phenotypic RIF-resistance do not harbor any known mutation in the rpoB gene, which may be explained by the fact that RIF resistance-conferring mutations are present elsewhere in the rpoB gene (such as a V146F and I572F) [ 42 , 43 ], suggesting that the nature and frequency of mutations in the rpoB gene vary considerably, between different geographical regions [ 44 ], by the fact that not all the mutations are targeted by the probes used [ 45 ], or as it has been reported that molecular assays still have some drawbacks, such as product cross contamination which is a major problem leading to false positive results [ 20 ]. The reason for this cross contamination has not been elucidated properly [ 46 ], but it may be due to laboratory procedures (protocol for pretreatment, DNA extraction, and detection of the amplification product) [ 47 ].…”