ABSTRACT
Objective To investigate the correlation between the mutation of pncA gene and the susceptibility to pyrazinamide ( PZA) in Mycobacterium tuberculosis complex ( MTBC) strains and to analyze the mutation of panD and rpsA genes in wild type isolates without pncA gene mutation.Methods The sus-ceptibilities of 108 MTBC strains to first-line drugs including PZA were detected by using the MGIT 960 TB system.PCR was performed to amplify the 16S rDNA and pncA, panD and rpsA genes.The PCR products were analyzed by DNA sequencing analysis .Results Among the 78 multidrug-resistant MTBC strains , 47 isolates (60%) were resistant to PZA.Four out of 30 (13%) strains that were sensitive to ethambutol , iso-niazid, rifampicin and streptomycin (EIRS) were resistant to PZA.The drug-resistant MTBC strains showed higher resistance rate to PZA than that of the EIRS sensitive strains .There were 49 ( 96%) PZA-resistant isolates and 4 (7%) PZA-sensitive isolates occurred pncA gene mutation.Most of the pncA gene mutations in the genomes of PZA-resistant strains were base substitution mutation , especially the His57Asp substitu-tion.The pncA gene mutations centralized in the regions of 160-169, 203-289, 309-396 and 413-467.Seven novel mutation sites of pncA gene were observed including T175C, C188A, G insertion at 68, AGC insertion at 235, C insertion at 339, CC insertion at 392 and GT deletion at 395.The mutation sites founded in the genomes of PZA-sensitive strains were different from those of the PZA-resistant strains .No mutation of the pncA gene and the upstream regulatory sequence was found in two PZA-resistant strains , NJ44 and NJ108 . The sequence analysis of panD and rpsA gene showed that the NJ 108 strain had panD gene mutation at G419A, but no mutation was detected in the NJ 44 strain.Conclusion The multidrug-resistant MTBC strains showed higher resistance rate to PZA .The pncA gene mutation was common in PZA-resistant MTB strains and the panD gene mutation was also worthy of attention .
ABSTRACT
Objective To investigate whether lipids and reagents would interfere the results when serum total bile acid(TBA) was measured by enzymatic cycling assay.Methods The serum TBA was measured by enzymatic cycling assay.The carry-over contaminations of high density lipoprotein(HDL-C),low density lipoprotein(LDL-C),cholesterol(TC),and triglyceride(TG)rea-gents were evaluated.In order to reduce the interference and carry-over contaminations,different washing procedures and detection sequence were set.Results By measuring the levels of TBA in pooled serums with low and high levels of lipids,the results showed that there was statistically significant difference between the groups with and without the addition of cleaning process before and af-ter TBA measurement(P <0.01).Cleaning with water might be more effective on reducing interference than those with acid solu-tion.Moreover,the mean of TBA levels in HDL-C,TC,TG and LDL-C reagents were (476.06 ± 1.88 ),(127.78 ± 1.18 ), (121.05±1.08),and (2.23±0.51)μmol/L,respectively.The stability of TBA level was greatly affected by HDL-C regents,fol-lowing by TC and TG reagents,and was little affected by LDL-C reagent.Setting up proper detection sequence and flushing proce-dures could obviously reduce the interference(P <0.01),but not completely rule out.Conclusion Analysis sequence and flushing procedures of biochemical analyzer as well as exogenous substance from reagents may seriously affect the accuracy of determination results.To ensure the accuracy and reliability of the results,it is necessary not only to set up reasonable irrigation and reaction se-quence,but also to master the instrument operation,to know the principle of test reaction and the components of reagents as well as equipment maintenance.