| Objective To study the features and regularities of mutation of katG, rpoB and rpsL drug-resistant genetic mutation in Mycobacterium tuberculosis L-forms among coal worker's pneumoconiosis patients complicated with tuberculosis in Huainan mining district, approach internal relationship between drug resistances and drug-resistant related genes, and to explore the value of clinical application by PCR-SSCP. Methods Sputum specimens of Mycobacterium tuberculosis L-forms were selected among typical pneumoconiosis patients complicated with tuberculosis, and cultivated, identified and extracted DNA. Then the PCR technique was amplified the mutational genes of katG, rpoB and rpsL. We must carry out the reversion test and traditional antimicrobial susceptibility test (AST). Finally we compared the gene mutational rates of strains of L-forms with those of popular types by PCR-SSCP, and the results were compared in order to analysis the mutational regularity.Results In research group, of total 52 Mycobacterium tuberculosis L-forms cases, PCR-SSCP assay can be used to detect the genes of katG, rpoB and rpsL, the rate of drug-resistance were respectively 57.70%(30/52), 65.38%(32/52) and 40.38%(21/52). Furthermore, the rate of reversion was 78.85%(41/52) and the result of drug-resistant genes was invariable. At the same time, we detected INH, RFP and SM by AST, the results were 76.92%(40/52), 90.38%(47/52) and 50.00%(26/52). Nevertheless, there were 10 strains of the negative of katG, 15 strains of the negative of rpoB and 10 strains of the negative of rpsL among persisters. Multi-drug resistant strains were 40(76.92%), including 21 strains (40.38%) resisting to 3 kinds of drugs, 19(36.54%) to 2 kinds of drugs and 12(23.08%) to single drug by AST. But there were 15 strains of allied mutation of three genes, 16 of two mutations and 6 of only one by PCR-SSCP. The coincidences were respectively 71.43%, 84.41% and 50.00%.While in contrast group, 28 general bacteric cases was found in sputum Mycobacterium tuberculosis culture positive, the results of katG, rpoB and rpsL by PCR-SSCP assay were 42.86%(12/28), 42.86%(12/28) and 32.14%(9/280), but those of INH, RFP and SM by AST were 64.23%(18/28), 60.71%(17/28) and 53.57%(15/28). Among multi-drug resistant strains were 20(71.43%), including 12 strains (42.86%) resisting to 3 kinds of drugs, 8 strains (28.57%) to 2 kinds of drugs and 6(21.43%) tosingle drug, but have 2 kinds of sensitive strains. Nevertheless, there were 6 strains of the negative of katG, 5 strains of the negative of rpoB and 6 strains of the negative of rpsL among persisters. Multi-drug resistant strains were 20(71.43%), including 12 strains (42.86%) resisting to 3 kinds of drugs, 18(28.57%) to 2 kinds of drugs and 6(21.43%) to single drug by AST.The difference of katG was not quite notable 0^=1.6062, P>0.05) at both L-forms and bacteric cases by PCR-SSCP assay, as well as rpoB and rpsL. By AST, we can find that RFP was quite notable (/2= 10.0137, P<0.005) , INH and SM were no. Conclusion The infectious rate of Mycobacterium tuberculosis L-forms in cases of pneumoconiosis complicated with tuberculosis is much high, and the status of drug resistance is pretty bad. PCR-SSCP technique has higher sensibility and specificity to detect to the genes of katG, rpoB and rpsL, to have advantages at earlier diagnosis and guidance of clinical medications. The generations of drug-resistance of L-forms were concerned not only with absence of cell wall, but also with the mutations of drug-resistant related genes.
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