Abstract: Objective To identify the proteins differentially expressed in isoniazid- and streptomycin-resistant Mycobacterium tuberculosis clinical isolate (INH/S^r isolate) compared with drug-sensitive clinical isolate (INH/S^s isolate) and H37Rv. Methods Whole cellular proteins were extracted from the INH/S^r isolate 02166, the INH/S^s isolate 01105 and H37Rv of M. tuberculosis, respectively. The proteins were digested with trypsin. The peptides were labeled, separated and identified by isobaric tags for relative and absolute quantitation (iTRAQ) combined with Nano LC-MS-MS technology. The bioinformatics were used to identify and quantify the proteins. Results One hundred and fifty three and 130 proteins were found differential expression in 02166 strain compared with 01105 strain and H37Rv, respectively, including 86 proteins in 02166 strain compared with both 01105 strain and H37Rv. The theoretical molecular weight and isoelectric point of differentially expressed proteins ranged from 7.63 to 326.22 and from 3.74 to 12.48, respectively. Differentially expressed proteins were mainly associated with intermediary metabolism, respiration, and lipid metabolism. Nine ribosomal proteins (Rv0056, Rv0651, Rv0652, Rv0701, Rv0719, Rv1630, Rv2785c, Rv2909c and Rv3458c) were commonly down-regulated in 02166 strain compared with both 01105 and H37Rv. Succinate-semialdehyde dehydrogenase (Rv0234c) and putative uncharacterized protein (Rv2466c) were common up-regulation (the ratios>1.2), and probable DNA-binding protein HU homolog hupB （Rv2986c） and putative uncharacterized protein (Rv2626c and Rv3118) were down-regulation (the ratios <0.5) in 02166 strain compared with both 01105 strain and H37Rv. Conclusion Differentially expressed proteins were identified in INH/S^r isolate compared with INH/S^s isolate and H37Rv using iTRAQ. Further study will focus on the above proteins playing role in INH or S resistance.

Key words: Mycobacterium tuberculosis, Isoniazid, Streptomycin, Proteomics