6%, respectively. A summary of all sequencing, DST, MIC and genotyping data is provided in
Additional file 2. Discussion In this study we carried out an in depth investigation of molecular resistance mechanisms by correlating SAHA HDAC mouse particular genomic variants with phenotypic resistance in clinical isolates from a high-incidence setting in West Africa. For INH and RIF there is a close correlation between data from molecular and phenotypic resistance testing for resistance determination in the strains analyzed. Sensitivity and specificity of sequencing of katG for detection of drug resistance were 86.7% and 100% and for sequencing of rpoB 100% and 93.8%, respectively. Overall, the correlation between molecular and phenotypic resistance testing for the determination of SM, EMB and PZA resistance was lower. Although specificities of sequencing of rpsL, embB and pncA were high (96-100%), sensitivities were lower (48-73%) due to so far BI 10773 ic50 unknown resistance mechanisms. However, while our results in principle support molecular resistance testing, the finding that especially in rpoB and also in pncA particular mutations are not linked to high-level resistance is challenging and demonstrates that careful interpretation of molecular resistance assays is mandatory. Therefore,
studies targeting new resistance mechanisms should include valid phenotypic resistance data and, to our opinion, a comprehensive database on genetic variations in resistance genes and the correlation with phenotypic resistance is necessary. Furthermore, the level of resistance mediated by particular Necrostatin-1 datasheet mutations and the clinical consequences need to be thoroughly investigated. Oxymatrine In addition, especially variations in gidB appear to be phylogenetically restricted rather than being involved in drug resistance development. In our study the most frequent mutation among INH resistant strains has been detected in katG at codon 315. This SNP has been observed in numerous prior studies [24, 25] and has clearly been correlated with INH resistance by loss of catalase activity. In two strains, in addition to variations at katG315, mutations at codon 291 and
471 were detected. However neither mutation has been described in the literature before and the katG315 mutation therefore represents the likely mechanism for INH resistance in these strains. The mutation at codon 300 observed in one strain in our study has been previously reported by Richardson and co-workers [26], where loss of this mutation has resulted in reversion of INH resistance in a previously drug resistant strain. The mutation at codon 302 as well as the insertion at codon 329 has not been described previously. Since they are restricted to INH resistant strains in our highly diverse MTBC collection, they represent potential new INH resistance mechanisms. Experimental evidence is required to validate this hypothesis.