耐异烟肼结核分枝杆菌临床分离株耐药相关基因突变研究

目的阐明结核分枝杆菌耐异烟肼临床分离株katG、inhA、ahpC、kasA及oxyR基因突变特点。方法对144株结核分枝杆菌临床分离株(耐异烟肼菌株101株;异烟肼敏感株43株)的katG、inhA、kasA、ahpC及oxyR基因进行DNA片断扩增及DNA序列分析,与GeneBank中结核分枝杆菌标准序列进行比较。结果(1)耐异烟肼菌株中未发现katG完全缺失,81株耐药株(80.2%)katG存在点突变、缺失或插入,其中16个突变位点未见报道;39株(38.6%)耐药株第315位点突变,低耐药菌株(1μg/ml)第315位点突变率显著高于高耐药菌株(10μg/ml;χ2=9.31,P<0.05);58株(57.4%)耐药株第463位点突变。23株(53.3%)敏感株第463位点突变。(2)5株(4.9%)耐药株inhA发生突变。敏感株inhA无突变。(3)3株(2.9%)耐药株ahpC发生突变。敏感株ahpC无突变。(4)17株(16.8%)耐药株kasA发生突变。敏感株中3株菌株Gly312Ser突变。(5)在全部菌株中未发现oxyR基因突变。(6)综合本项研究中各基因的突变情况,共有91株耐异烟肼菌株发生与异烟肼耐药相关的突变。结论本项研究进一步证实了结核分枝杆菌耐异烟肼与katG、inhA、ahpC及kasA基因突变之间的关系,并且提示还有其他机制参与异烟肼耐药。     

结核分枝杆菌katG S315T突变频率及突变株特征的研究

近年来分子遗传学研究表明，异烟肼（INH）耐药机制复杂，涉及多个基因，至少包括katG、inhA、kasA以及ahpC等基因。研究表明，INH耐药与编码过氧化氢酶．过氧化物酶的katG基因突变的联系最强，其中katG基因的一种特定替换，315位密码子的AGC→ACC（Ser→Thr，或katG S315T）颠换报道最多。该突变可降低INH耐药菌株中过氧化氢酶活性，但可保持足够水平的该酶的过氧化物酶活性，后者为细菌解毒所必需。世界各地结核分枝杆菌菌株中，katG S315T突变的流行率一般为26．0％～93．6％，结核病高发区流行率高。在俄罗斯圣彼德堡地区，该突变还与耐多药性有关，在荷兰该突变亦与高水平耐药、耐其他药物有关。研究我国农村耐多药结核病（MDR-TB）高发地区INH耐药分离株中katG S315T突变的发生频率与突变株特征有利于耐药结核病的防治。     

基因芯片技术检测贵州省结核分枝杆菌耐药基因KatG和inhA

目的 了解本地区结核分枝杆菌(MTB)异烟肼(INH)相关耐药基因katG和inhA的突变特征,评价基因芯片法对MTB INH耐药性检测的临床应用价值。方法 应用基因芯片法对经PCR-荧光探针法鉴定为MTB阳性的2 738例病人标本进行INH耐药性检测,分析其相关耐药基因katG和inhA的突变特征,同时应用比例法检测上述同期送检的相同病人的同类型标本经罗氏培养MTB阳性菌株的INH耐药性,比较两种方法的检测结果。结果 2 738例MTB核酸阳性标本经基因芯片法检测,INH耐药465例,耐药率16.98%,其中以katG 315(AGC→ACC)突变为主,基因突变率为78.06%,其次为inhA -15(C→T),katG 315(AGC→AAC),突变率分别为16.13%和5.59%。上述病人同期送检的同类型标本有1 493例经罗氏培养MTB阳性,比例法检测,INH耐药255例,耐药率17.08%,对应的基因芯片法检测结果为INH耐药249例,耐药率16.68%。以比例法结果为判断标准,基因芯片法测定INH耐药性的敏感性、特异性、阳性预测值(PPV)、阴性预测值(NPV)及准确性分别为85.49%、97.50%、87.55%、97.03%和95.45%。结论 本地区INH耐药以katG 315(AGC→ACC)和inhA -15(C→T)突变类型为主;基因芯片对MTB INH耐药性检测具有高敏感性、特异性、准确性和快速性,可用于本地区MTB INH耐药性的快速检测。     

31株结核分枝杆菌异烟肼耐药相关基因检测及序列分析

目的了解贵阳地区分离的结核分枝杆菌katG基因、inhA启动子和oxyR-aphc间隔区基因突变特征。方法对31株结核分枝杆菌临床分离株（异烟肼耐药株17株,异烟肼敏感株14株）的katG基因、inhA启动子和oxyRaphc间隔区进行DNA片段的PCR扩增,并进行测序分析。结果 17株异烟肼耐药菌株中有16株检出katG基因突变,其中70.5%（12/17）为315位密码子变异,且变异类型均为AGC→ACC,敏感株未发现315位点突变。11株敏感菌和4株耐药菌在463位密码子发生变异,变异类型均为CGG→TGG,变异率分别为78.6%（11/14）和23.5%（4/17）,差异无统计学意义。有12株耐药株的变异类型为katG基因双重位点突变,其中10株为katG315（AGC→ACC）和463（CGG→TGG）位变异,463（CGG→TGG）和299（GGC→AGC）变异及463（CGG→TGG）和419（GAC→CAC）位变异各1株。2株异烟肼耐药菌检出oxyR-aphC启动区G32A突变,其中1株为联合katG463和299位突变。结论贵阳株结核杆菌菌株异烟肼耐药基因突变具有多态性,主要的变异类型为katG315位点突变。     

徐州市耐多药结核耐药分析及分枝杆菌基因突变特征研究

目的 研究徐州市耐多药结核(MDR-TB)耐药表型、耐INH或RFP相关基因突变情况,分析耐药表型与基因突变间关系,为耐多药结核疾病的诊断提供科学依据。方法 采取随机方法抽取徐州市115例MDR-TB菌株和66株全敏感菌株进行耐药情况分析,使用基因芯片检测技术对耐INH相关基因katG、 inhA和aphC以及耐RFP相关基因rpoB突变位点进行检测,对结果进行t检验分析。结果 徐州市MDR-TB菌株耐药表型有9种组合,主要是以耐INH+RFP组合为主,比例为47.83%,其次为耐INH+RFP+SM组合,比例为20.00%。与耐INH的相关基因突变率87.83%,基因突变类型分别为单基因katG(64.35%)和inhA(3.48%),双基因katG+inhA(12.17%)和katG+aphC(12.17%)。耐多药株(115例)和敏感株(66例)总体变异率均数比较(t=107.56,P<0.05), 其中katG基因突变率比较(P<0.05),二者差异均有统计学意义。与耐RFP相关rpoB基因总突变率86.09%,耐RFP相关rpoB基因突变类型分别为单531(45.22%)、516(8.70%) 和526位点,双(531+516)(13.91%)、(531+513)(12.17%)和516+533突变位点, 531+516+513(3.48%)三位点突变。耐多药株和敏感株总体和单个位点突变率均数比较(t=94.92,P<0.05), 531(P<0.05)、516(P<0.05)、533(P<0.05),二者差异均有统计学意义。结论 研究发现了徐州市MDR-TB耐药表型特征。徐州市MDR-TB菌株与耐INH和RFP相关基因突变客观存在,并表现出多态性和地区性。与耐INH相关katG基因、与耐RFP的相关rpoB基因531、516、533位点突变相对稳定,有临床应用价值,可作为徐州市耐药结核菌株快速诊断的指标。     

华东地区耐药结核分枝杆菌katG基因的变异

目的了解我国华东地区结核分枝杆菌中与异烟肼耐药相关的katG基因的变异情况，提供我国异烟肼耐药相关的基因谱。方法对429株结核杆菌行核酸抽提后先以限制性酶切片段多态性方法检测有无最常见的耐药相关S315T突变，对未发现S315T突变的异烟肼耐药株取部分行katG全基因测序以了解其他位点的变异情况。结果耐药结核分枝杆菌中76．9％（166／216）存在katG基因$315T突变。发现有2株异烟肼高度耐药株中存在katG基因片段的缺失。48株异烟肼耐药株测序结果发现katG基因突变特点如下：突变率较高的有315、463、234位点，其余突变位点较多而分散。315位密码子的突变中除S315T外，S315N突变形式也较常见，占8．7％。结论结核分枝杆菌耐药机制复杂，了解耐药相关基因的变异情况是建立可靠的耐药性分子检测方法的基础。     

基因芯片快速检测结核分枝杆菌katG基因突变及其与异烟肼耐药相关性

目的了解结核分枝杆菌katG基因S315突变与异烟肼（isoniazid,INH）耐药相关性,建立快速简便的katG基因S315突变基因芯片检测方法。方法采用二倍稀释法检测123株结核分枝杆菌临床分离菌株对INH的耐药性。PCR及测序确定上述结核分枝杆菌katG基因S315位点突变率及突变类型。根据PCR及测序结果,设计Cy3荧光标记探针并制备katG基因S315位点突变检测基因芯片。基因芯片检测结果与PCR及测序结果进行对比分析。结果 123株结核分枝杆菌临床菌株中,39.0%（48/123）菌株对INH敏感,61.0%（75/123）菌株对INH耐药。结核分枝杆菌H37Rv株及所有临床菌株均能扩增出katG基因片段。75株INH耐药菌株中,69.3%（52/75）菌株katG基因出现S315位突变,其中25株突变类型为S315N（AGC→AAC）、12株为S315T（AGC→ACC）、7株为S315I（AGC→ATC）、各有3株分别为S315T（AGC→CGC）和S315R（AGC→AGA）、2株为S315G（AGC→GGC）。所制备的基因芯片对123株结核分枝杆菌katG基因S315野生型或突变型检测结果与PCR及测序结果完全一致。结论结核分枝杆菌katG基因S315突变与INH耐药密切相关。本研究中制备的基因芯片可快速、简便、准确、敏感和特异地检测结核分枝杆菌katG基因S315突变及其类型。     

结核分枝杆菌对异烟肼和利福平的耐药水平与其耐药基因突变的相关性研究

目的 探讨Mtb耐药相关基因katG、inhA、oxyR-ahpC突变与对INH的耐药水平及rpoB突变与对RFP的耐药水平的关系。 方法 采用微孔板Alamar blue显色法分别检测59株耐INH的Mtb临床分离株对INH和30株耐RFP菌株对RFP的最低抑菌浓度（the minimum inhibitory concentration,MIC）,同时用直接测序法检测对INH耐药菌株katG、inhA、oxyR-ahpC和对RFP耐药菌株rpoB的突变情况。 结果 INH MIC为0.2500~1.0000 μg/ml（低水平耐药菌株）和 MIC≥2.0000 μg/ml（高水平耐药菌株）的INH耐药株,inhA启动子突变率前者高于后者［53.8% (7/13),4.3% (2/46)］,katG 315突变率前者低于后者［15.4% (2/13),76.1% (35/46)］,χ²值分别为15.57和13.48,P值均为0.000。RFP MIC为0.5000～16.0000 μg/ml和MIC≥32 0000 μg/ml的RFP耐药株,rpoB 531和526位总突变率前者低于后者［62.5% (5/8),95.5%(21/22)］,P_确切概率＝0.048。 结论 INH耐药菌株inhA启动子突变与INH低水平耐药有关,katG 315突变与INH高水平耐药有关;rpoB 531和526位突变与RFP高水平耐药有关。     

福建省结核分枝杆菌异烟肼耐药相关基因突变特征初步分析

目的 了解福建省结核分枝杆菌异烟肼耐药相关基因的突变特征,为异烟肼耐药快速检测方法的建立提供一定的科学依据。方法 对来源于福建省结核病耐药性监测30个监测点纳入的75株耐多药和10株全敏感结核分枝杆菌分离株,进行katG、inhA、oxyR-ahpC基因片段PCR扩增并测序分析,用RD105缺失基因检测法进行北京家族基因型鉴定,使用卡方检验分析相关性。结果 10株全敏感株未检测到突变。75株耐多药结核分枝杆菌检测到72株katG、inhA、oxyR-ahpC发生单一或联合基因突变,突变率为96.0%(72/75)。其中,65株(86.7%,65/75)发生katG突变,涉及5个位点,最常见位点突变的密码子是315,突变率为82.7 %(62/75),最常见突变形式为Ser315Thr(77.3%,58/75);8株(10.7%,8/75)发生inhA突变,突变形式均为C(-15)T;5株(6.7%,5/75)发生oxyR-ahpC突变,突变形式为C(-39)T或C(-46)A。katG、inhA和oxyR-ahpC 在北京家族基因型菌株和非北京家族基因型菌株中的突变率分别为83.9 %(47/56)、12.5%(7/56)、7.1 %(4/56)和94.7 %(18/19)、5.3 %(1/19)、5.3 %(1/19),差异无统计学意义(P值分别为0.23、0.38、0.78)。结论 福建省结核分枝杆菌异烟肼耐药性相关基因突变绝大多数发生在katG、inhA和oxyR-ahpC基因位点,且以katG突变为主。初步分析显示北京家族基因型菌株流行与异烟肼耐药基因突变特征无关。     

重庆市肺结核患者异烟肼与丙硫异烟胺耐药状况分析

目的 了解重庆市结核分枝杆菌异烟肼(INH)、丙硫异烟胺(Pto)及其交叉耐药情况,为重庆市耐药结核病的防控提供参考。方法 根据重庆市2015-2017年39个区县培养阳性菌株的传统药敏试验结果,收集288例INH或Pto任意耐药菌株,分析其耐药情况。结果 288例菌株中,INH耐药菌株285例,Pto耐药菌株19例,交叉耐药菌株16例。复治患者INH 或Pto的耐药率均高于初治患者,年龄15~44岁患者Pto耐药率显著高于INH组。Pto耐药组Pre-XDR-TB及Ofx耐药率显著高于INH组。交叉耐药菌株中,年龄15~44岁组交叉耐药率较高,且 MDR-TB发生率高达93.8%。结论 重庆市INH与Pto耐药情况已较为严重,医生在为INH耐药患者制定化疗方案时应根据药敏结果,应谨慎选择Pto进行替代治疗,以避免更多耐药的发生。     

Genomic mutations in the katG, inhA and aphC genes are useful for the prediction of isoniazid resistance in Mycobacterium tuberculosis isolates from Kwazulu Natal, South Africa.

Genotypic analysis of isoniazid (INH) resistance in 79 isolates of M. tuberculosis (MTB) was undertaken by PCR-single strand conformation polymorphism (SSCP), Msp1 restriction enzyme analysis and sequence analysis of specific regions of three genes (part of the coding sequence of katG, and promoter regions of the inhA operon and ahpC) in order to determine the particular allelic variants within these genes. The epidemiologic relatedness was determined using IS6110 and polymorphic G-C region (PGRS (MTB484(1)) based restriction fragment length polymorphism (RFLP). Mutations in katG, inhA locus and ahpC were identified in 77/79, 19/79 and 10/79 isolates respectively. The ability of PCR-SSCP to detect mutations associated with INH resistance in katG, inhA and ahpC genes was 100% (CI 91.2-99.7%), 98.7% (CI 74.0-99.9%), and 100% (CI 69.2-100%) respectively. Specificity was 100%. All isolates with mutations in the 209 bp fragment of the MTB katG gene containing the Ser315Thr codon were positive by PCR-RFLP using Msp1 enzyme restriction analysis. Sixteen of 19 isolates with alterations on the 3' end of the ribosome binding site upstream of mabA in inhA locus simultaneously harbored Ser315Thr mutations in KatG. In 9/10 isolates, mutations in the ahpC promoter region were located in the 105 bp oxyR-ahpC intergenic region. None of 17 INH drug susceptible isolates harbored mutations in any of the three genetic regions, although the katG1 allele (Arg 463 Leu) was present in one isolate. Characterization by IS6110/PGRS(MTB484(1))RFLP analysis revealed that a number of drug resistant clones are widespread in the community. We conclude that the frequency of the Ser315Thr katG mutation in the local strain population makes the PCR-RFLP MTB katG assay a reliable, rapid and useful method for detecting INH resistance.     

Mutations responsible for Mycobacterium tuberculosis isoniazid resistance in Italy.

SETTING: The incidence of tuberculosis (TB) and drug resistance in Italy is low compared to other countries. Mutations in several genomic regions of Mycobacterium tuberculosis are involved in the occurrence of isoniazid (INH) resistance. OBJECTIVE: To investigate the mutations responsible for INH resistance among Italian isolates of M. tuberculosis, to assess the feasibility of predicting drug resistance using a genetic approach. DESIGN: The mutations responsible for INH resistance were looked for in selected regions of genes katG, kasA and ndh and in the promoter regions of inhA and ahpC by nucleotide sequencing, and the results were compared with data reported in other studies. RESULTS: Prevalent INH resistance mutations were found at codon 315 of the katG gene and at position -15 of the inhA regulatory region (respectively 37.8% and 20.0% of isolates). The prevalence of mutations at position -24 of inhA, in ahpC, and in kasA ranged from 2.2% to 4.4%. No mutations were found in 35.6% of the isolates. CONCLUSION: The identification of INH resistance by genetic analysis of the selected regions may be inappropriate in areas with a low prevalence of TB, such as Italy, as the genetic mechanisms of resistance remain unidentified for approximately one third of the isolates.     

Anti-drug pattern of drug-resistant Mycobacterium tuberculosis and analysis of mutation in drug-target genes

The antimycobacterial susceptibility test was performed and minimal inhibitory concentration (MIC) to drugs was determined in 98 strains of Mycobacteium tuberculosis (MTB) isolated in Tokyo from 2000 to 2003, to find which were resistant to any of the four main anti-MTB drugs, isoniazid (INH), rifampicin (RFP), streptomycin (SM), and ethambutol (EMB). 27strains of them were resistant only to SM, and 16 strains were resistant only to INH. 51 strains of them were resistant to not only INH but also other drugs. 38 strains were resistant to both INH and RFP. 19 strains were resistant to all four drugs, including 7 strains resistant to new quinolon anti-biotics also. Nucleotide or amino-acid mutations in drug resistant MTB genome were determined by DNA sequencing method. Mutation of codon 516, 526, or 531 of rpoB gene was detected in 98% of MTBs resistant to RFP. Deletion or insertion of katG gene or nucleotide mutation at regulatory region of ahpC gene was detected in MTBs highly resistant to INH. Amino acid mutation of katG gene, especially at codon 315, was detected in MTBs resistant to INH intermediate. Nucleotide mutations at regulatory region of inhA gene were detected in MTBs resistant to INH at low level. Amino acid mutation at codon 43 or 88 of rpsL gene was detected in MTBs highly resistant to SM, and nucleotide mutation at 512, 513, or 516 of rrs gene was detected in MTBs resistant to SM at low level. Amino acid mutation at codon 306 of embB gene was detected in 87% of MTBs resistant to EMB.     

Resistance-conferring mutations of Mycobacterium tuberculosis strains with low level resistance to isoniazid

OBJECTIVE: We investigated the prevalence of isoniazid (INH) resistance-conferring mutations in the INH-indeterminate Mycobacterium tuberculosis (MTB) strains. MATERIALS AND METHODS: We initially selected a sample of 47 clinical isolates of MTB from patients, who visited the Osaka Prefectural Medical Center for Respiratory and Allergic Diseases from 2000 to 2005. Strains resistant to the concentration of 1 - 2 microg/ml were defined as "indeterminate". INH resistance-conferring mutations were determined by DNA microarray. RESULTS: Of 47 INH-indeterminate strains, only 13 (27.7%) were found to have no resistance mutations, 23 (48.9%) had mutation within the inhA regulatory region at -15 C to T, and 2 (4.3%) had mutation within the inhA regulatory region at -8 T to A, 6 (12.8%) had mutation within the katG gene at 1778 G to A, and 3 (6.4%) had mutations within the katG gene both at 1778 G to A and at 982 T to G. CONCLUSIONS: We showed that the majority of INH-indeterminate strains have resistance-conferring mutations, which were mainly detected within the inhA regulatory region.     

Genotypic analysis of isoniazid and rifampin resistance in drug-resistant clinical Mycobacterium tuberculosis complex isolates in southern Turkey

In this study we aimed to learn about the nature and frequency of katG, inhA, and rpoB gene mutations underlying isoniazid (INH) and rifampin (RMP) resistance in clinical Mycobacterium tuberculosis complex isolates. The Silver Sequence DNA sequencing method was used to detect the resistance condition of 22 INH, 6 RMP, and 13 INH and RMP in previously determined drug-resistant clinical M. tuberculosis isolates. Thirty of 35 (85.7%) INH-resistant strains and 14 of 19 (73%) RMP-resistant strains were found to have a mutation in the analyzed katG gene fragment or inhA locus and rpoB gene fragment. In the katG gene region, the codons of mutation detected were determined to be 315 (23 of 30, 76.6%), 279 (4 of 30, 13.3%) and 293 (1 of 30, 3.3%), a finding that has not been reported previously. Our findings demonstrated that the most frequent mutation pattern was Ser315Thr at codon 315 with a rate of 60% (18 of 30). In 5 (16.6%) isolates, a nucleotide change was detected which is associated with INH resistance from -15(th) C to T in the inhA locus. In the rpoB gene region, codons possesing point mutations were 531 (9 of 14, 64.2%), 516 (1 of 14, 7.1%), 524 (1 of 14, 7.1%), and 545 (4 of 14, 28.6%), which has not been reported previously. We believe about that our present study supplies important data on the different kinds of mutations occurring at various target loci for associated RMP and INH resistance in clinical isolates of our restricted region.     

Use of fluorescence resonance energy transfer for rapid detection of isoniazid resistance in Mycobacterium tuberculosis clinical isolates.

SETTING: Rapid detection of drug resistance in Mycobacterium tuberculosis is important to select effective treatment and prevent transmission of resistant isolates. OBJECTIVE: To evaluate the use of fluorescence resonance energy transfer (FRET) for rapid detection of isoniazid (INH) resistance in M. tuberculosis clinical isolates. DESIGN: One hundred INH-resistant and 50 INH-susceptible isolates of M. tuberculosis were included in the study. The drug susceptibility of all isolates was determined by the standard agar proportion method, and all isolates were then tested by FRET. Three genes associated with INH resistance, katG, inhA and ahpC, were analysed. All isolates were amplified with three pairs of primers. Three pairs of fluorescently labelled DNA probes specific to codon 315 of katG, nucleotide 209 in the regulatory region of inhA and a frequent mutation site in the intergenic region of oxyR-ahpC, were used for mutation detection. RESULTS: The results obtained using FRET were compared with those from the proportion method. The sensitivity and specificity of FRET were respectively 76% and 100%. The frequencies of mutations were 48% in katG, 17% in inhA, 8% in ahpC, 2% in inhA-ahpC and 1% in inhA-katG. CONCLUSION: FRET is a rapid, specific method that can be useful to detect INH resistance in M. tuberculosis clinical isolates.     

深圳市耐多药结核分枝杆菌流行株耐药基因序列分析

目的 了解深圳市耐多药结核分枝杆菌（multidrug-resistantMycobacterium tuberculosis ,MDR-TB）的分子流行病学特征。 方法 参照WHO/IUATLD标准,使用L-J药敏培养基,采用1％比例法药敏试验筛选出敏感株和异烟肼（isoniazid,INH）、利福平（rifampicin, RFP）双耐药临床分离株,通过DNA测序检测深圳地区153株敏感株与132株MDR-TB的INH耐药基因 kat G、inh A、oxy R- ahp C基因间区域及RFP耐药基因 rpo B碱基排列顺序,运用DNASTAR和blastn进行序列分析。 结果 153株敏感株突变率为27.5%（42/153）。132株MDR-TB突变率为98.5%（130/132）,其中kat G基因突变率为73.5%（97/132）,68.9%（91/132）为 kat G315位突变; inh A基因突变率为18.2%（24/132）,11.4%（15/132）为启动子区域突变,未发现 inh A94特异突变株; ahp C基因突变率为16.7%（22/132）,10.6%（14/132）为启动子区域突变; rpo B基因81-bp核心区域突变率为93.2%（123/132）。 结论 kat G315、inh A启动子区域、ahp C启动子区域以及 rpo B 81-bp核心区域突变为深圳地区耐多药结核分枝杆菌主要突变类型,与其他国家和地区差异无统计学意义;但深圳地区未见 inh A94突变株。     

Molecular analysis of isoniazid, rifampin and streptomycin resistance in Mycobacterium tuberculosis isolates from patients with tuberculosis in Düzce, Turkey

The aim of this study was to use DNA sequencing analysis to analyze the mutations in the most commonly targeted genes (katG, inhA, rpoB, rpsL) in isoniazid (INH)-, rifampin (RIF)- and streptomycin (SM)-resistant Mycobacterium tuberculosis strains obtained from subjects in Duzce, Turkey. Four isolates were found to be INH-resistant, 3 were RIF-resistant and 5 were SM-resistant, out of a total of 52 M. tuberculosis strains. In 3 of the 4 INH-resistant strains, a mutation in the katG gene in codon 315 appeared as AGC-->ACC (Ser-->Thr), and the other INH-resistant strain showed a mutation in the katG gene in codon 314 as ACC-->CCC (Thr-->Pro). There were no mutations in the inhA gene in INH-resistant isolates. Two of the 3 RIF-resistant strains were found to have mutations in the rpoB gene in codon 516 appearing as GAC-->GTC (Asp-->Val), and the other RIF-resistant strain has a mutation in the rpoB gene in codon 531 as TCG-->TTG (Ser-->Leu). These 3 RIF-resistant strains are also INH-resistant. All 5 SM-resistant strains have mutations in the rpsL gene in codon 43 appearing as AAG-->AGG (Lys-->Arg). Thus, we found common gene mutations that bring about the resistance of M. tuberculosis to antituberculosis drugs in all of our isolates from Duzce. To the best of our knowledge, the ACC-->CCC (Thr-->Pro) mutation in the katG gene in codon 314 has not been previously defined.