To Explore The Reasons Why Isoniazid Susceptibility Results Are Inconsistent By Rapid Liquid Mediums Cultured Method And L-J Cultured Method

Objective:To explore the reasons why isoniazid susceptibility results are inconsistent by BACTEC MGIT960rapid liquid mediums cultured method and Lowenstein-Jensen cultured method.Methods:(1)20pairs of clinical isolates those isoniazid susceptibility results are inconsistent by BACTEC MGIT960rapid liquid culture mediums cultured method and L-J cultured method. Each pair of bacterial strain can be divided into group a (BACTEC MGIT960rapid cultured results of isoniazid resistance) and group b (L-J to isoniazid sensitive cultured method results).(2)20pairs of mycobacterium tuberculosis strains’ genotypes were identified by VNTR and Spoligotyping genotyping and determined whether to homologous strains.(3)To evaluate the isoniazid resistance by means of mycobacterium tuberculosis INH resistance gene sequencing.(4) Two methods of Brooth7H9liquid cultured medium and L-J medium were respectively accepted to determine the INH MIC of the20pairs of strains those isoniazid susceptibility results are inconsistent by BACTEC MGIT960rapid liquid cultured mediums and L-J cultured method.Results:(1) The results of Spoligotyping and VNTR genotypes:16pairs of results were consistent,3pairs of results were inconsistent.(2) The results of isoniazid resistance gene by gene sequencing:in those16pairs of tuberculosis clinical isolates,12pairs had INH gene mutation,3pairs had no INH gene mutation,1pairs had indeterminacy; in those4pairs of tuberculosis clinical isolates,3pairs had INH gene mutation,1pairs had no INH gene mutation. The total coincidence rate of MGIT960system:π=12/15=80%. The total coincidence rate of L-J:π=3/15=20%(3)The isoniazid MIC values of group a were compared with between7H9liquid cultured method and L-J solid cultured method, P=0.000<0.05, statistically significant. The isoniazid MIC values of group b were compared with between7H9liquid cultured method and L-J solid cultured method, P=0.000<0.05, statistically significant.Conclusion:(1)16pairs whose results were consist by Spoligotyping and MIRU were homologous strains.4pairs whose results were nonconsist by Spoligotyping and MIRU were non-homologous strains, which explained that there were multiple infection in those patients.(2) In those16pairs of tuberculosis clinical isolates,12pairs had INH gene mutation,which were in consist with susceptibility results of BACTTEC MGIT960.3pairs had no INH gene mutation, which were in consist with susceptibility results of L-J.1pairs had indeterminacy.(3) The isoniazid MIC values of12pairs which were compared with between7H9liquid cultured method and L-J solid cultured method were nonconsist, and the isoniazid MIC values by L-J solid cultured method were significantly higher than that of7H9liquid cultured method. The drug susceptibility results of20pairs clinical strains were in line with the high degree to genetic sequencing results. It should be considered the different MIC and the critical value of different methods of drug susceptibility.(4) Some drug susceptibility results of special resistant strains were statistically significant when they were made use of BACTEC MGIT960rapid liquid cultured mediums and L-J cultures. when we evaluate the resistance, it should be considered the difference by different methods of drug susceptibility,be understanded multiple infection, heterosesistance,and the degree of resistance. Which could preferably guide the use of clinical drug and individualized treatment, and more effectively control the spread of TB and drug-resistant TB.