Abstract: Objective To evaluate the resistance to cycloserine (Cs) and p-aminosalicylic acid (PAS) in multi-drug resistant (MDR) M. tuberculosis isolates, and analyze the relationship between the genotype and drug-resistant phenotype, which will provide the scientific evidence for MDR-tuberculosis treatment.  Methods One hundred and ninety-six MDR-M.tuberculosis isolates were collected from the first tuberculosis drug resistance survey of China conducted in 2007, were detected their minimum inhibition concentrations (MICs) of Cs and PAS by microplate Alamar blue assay, and were analyzed the genotypes by Spoligotyping method. Cs and PAS resistant rates between Beijing genotype and non-Beijing genotype strains were compared using Chi square test, P<0.05 was considered as statistically significant difference.  Results Of 196 MDR-M. tuberculosis isolates, 22.4%（44/196） were resistant to Cs, and 17.3%（34/196） were resistant to PAS. 82.7%（162/196）isolates belonged to Beijng geno-type, while 17.3%（34/196） strains belonged to non-Beijing genotypes. Of 162 Beijing genotype strains, 21.0% （34/162）strains were resistant to Cs, while 29.4%（10/34） of non-Beijing genotype strains were resistant to Cs. There were no statistical difference in Cs-resistant rates between Beijing and non-Beijing genotype strains（χ²=1.15，P>0.05）. 16.0%（26/162）of Beijing genotype strains were resistant to PAS, while 23.5% (8/34) of non-Beijing genotype strains showed the resistance to PAS. They had no significant difference（χ²=1.10，P>0.05）.  Conclusion The Cs- and PAS-resistant rates in MDR-M. tuberculosis strains were high in China. Beijing genotype was the predominant among MDR-M. tuberculosis isolates in China. The Cs- and PAS-resistant rates between Beijing and non-Beijing genotype strains had no significant difference.

Key words: Mycobacterium tuberculosis, Drug resistance, multiple, bacterial, Cycloserine, Aminosalicylic acid, Genotype