探针熔解分析法检测结核分枝杆菌异烟肼耐药突变的应用和评价

目的 评价PMA技术检测MTB对INH耐药突变的价值,调查INH耐药突变发生特征.方法 MTB标准株H37Rv来自国家结核病参比实验室,1株INH敏感株和1株katG S315TACC突变株来自厦门市疾病预防控制中心,7株含有已知INH耐药突变的结核耐药株来自深圳慢性病防治中心、河南省疾病预防控制中心、中国人民解放军第309医院和厦门市疾病预防控制中心.707份MTB临床分离株来自厦门市疾病预防控制中心、厦门市第一医院和漳州市疾病预防控制中心,126份MTB涂阳痰标本来自厦门市同安区疾病预防控制中心.MTB标准株H37Rv、7株MTB INH耐药株和833份临床标本均采用厦门致善结核分枝杆菌异烟肼耐药突变检测试剂盒热裂解法提取基因组DNA,1株INH敏感株和1株katG S315T ACC突变株采用AxyPrepTM细菌基因组DNA提取试剂盒提取基因组DNA.熔解曲线分析所检标本与野生型对照在katG315位密码子、inhA启动子区(- 17～-8位点)、ahpC启动子区(-44～-30以及-15 ～3位点)及inhA94位密码子的熔解温度(Tm值)差异判断标本是否发生INH耐药突变.3×105拷贝/反应的野生株和katG S315T ACC突变株以10倍梯度稀释至300拷贝/反应,分析PMA技术的灵敏度.用PMA技术检测7株含有已知INH耐药突变的结核耐药株,评价特异性,并就其中5种耐药突变进行重复性检验.测序验证PMA技术对833份标本INH耐药性的临床检测效能.结果 PMA技术从核酸提取到结果判断可在3小时内完成,在标准96孔实时PCR仪器上可同时检测46份标本.对野生株和katG S315T ACC突变株的灵敏度均为300拷贝/反应,能够同时区分9种INH耐药相关点突变或缺失,5种耐药突变的Tm值标准偏差均在0.5℃之内.检出的162份突变标本与测序验证结果均一致.临床标本验证突变率为19.4％( 162/833),在所检出的14种INH耐药突变katGS315T( AGC →ACC)、inhA启动子区- 15C→T和katG S315N (AGC→AAC)这3种突变占INH耐药突变标本的83.3％(135/162).结论 PMA技术可快速、灵敏、特异检测结核INH耐药突变.     

家族性高胆固醇血症患者二例的LDLR基因复合杂合新突变分析

目的 探讨2例临床确诊的湖北籍FH患者的LDLR基因突变状况,为FH的基因诊断提供依据.方法 收集2例临床确诊的FH患者及其父母血脂检测指标等临床资料,通过PCR扩增LDLR基因的1～18个外显子和内含子区域,再将扩增产物进行正、反双向核苷酸序列分析,并与GenBank中LDLR基因的正常序列对比找出突变后,结合FH先证者的临床表型证实致病突变的类型.结果 氧化酶法测定1号、2号FH先证者血浆TC,分别为12.79、11.98 mmol/L;经核苷酸序列分析,其ApoB100基因涵盖的3 500～3 531区域均未见突变;LDLR基因均为复合杂合突变,1号FH先证者LDLR基因第4外显子的665位碱基G>T为杂合错义突变,且该突变为新的点突变,第9内含子的1 358+32位碱基C>T突变也为新的点突变,并均由其父母遗传.2号先证者第9外显子1 257位碱基C>A突变导致终止密码子提前出现,但其核苷酸改变与比利时报道的C>G不同,第13外显子检测到1 879位碱基G>A杂合错义突变,且分别来源于其父母.结论 2例FH先证者均存在LDLR基因复合杂合突变,1号FH先证者的第4外显子665位碱基G>T和第9内含子1 358+32位碱基C>T、2号FH先证者的第9外显子1 257位碱基C>A突变均为新突变,这可能是导致FH的分子机制.

Abstract：

Objective To determine LDLR gene mutation in 2 clinically diagnosed FH patients from Hubei province and provide basis for gene diagnosis of FH.Methods Clinical data of 2 FH patients and their parents were collected.The promoter region and exon 1 to exon 18 region of LDLR gene were amplified through PCR and the amplified products were analyzed by forward and reverse DNA sequencing.The mutations were identified after comparison with LDLR gene sequence in GenBank.The pathogenic gene mutations were confirmed according to both genotype and phenotype of FH probands.Results The levels of plasma TC of two probands were 12.79 and 11.98 mmol/L.respectively.No gene mutations were detected in region 3 500 to 3 531 of ApoB100. The mutations of LDLR gene were compound heterozygous mutations. The novel mutation 665G > T detected in the exon 4 of No. 1 proband's LDLR gene was heterozygous missense mutation. The novel mutation 1 358 +32C > T was detected in the exon 9 of No. 1 proband's LDLR gene.The mutations 665G > T ( paternal origin) and 1 358 + 32C > T ( maternal origin) were inherited from the parents. A novel mutation 1 257 C > A was detected in the exon 9 of No. 2 proband's LDLR gene, resulting the presence of a premature termination codon, which was different from 1 257 C > G reported in Belgium.Another heterozygous missense mutation 1 879 G > A was detected in exon 13. They were derived from paternal origin and maternal origin, respectively. Conclusions There are three novel gene mutations:665G >T, 1 358 +32C > T, 1 257C > A found in two probands with compound heterozygous mutations in LDLR respectively. They maybe play a potential role in FH pathogensis.     

肺炎克雷伯菌药敏分析及其超广谱β内酰胺酶基因分型研究

目的 对北京大学人民医院分离的肺炎克雷伯菌进行药敏分析及ESBL型别测定,为控制院内肺炎克雷伯菌感染提供依据.方法 收集北京大学人民医院2001-2007年分离的1 205株肺炎克雷伯菌,采用Vitek-2全自动药敏鉴定分析仪对菌株进行鉴定及药敏试验,采用WHONET 5.3软件进行药敏结果分析,PCR法检测ESBL基因型别,比较分析各种药物敏感率和基因型比率特征和差异.结果 2001-2007年肺炎克雷伯菌中产ESBL比例逐年增加:2001年为15.8% (40/253),2002年为20.9% (53/253),2003年为32.8% (42/128),2004年为32.8% (45/137),2005年为36.6% (60/164),2006年为45.3% (68/150),2007年为45.6% (73/160).ESBL阳性菌株中SHV基因检出比例最大,2007年为83.6%(61/73).ESBL阳性菌株中CTX-M基因检出率逐年增加,2007年为54.8%(40/73).携带单一SHV基因菌株与同时携带SHV、CTX-M基因菌株对头孢他啶、头孢曲松及头孢噻肟的耐药率差异有统计学意义(χ2值分别为20.26、32.03、29.65,P均＜0.05);携带单一SHV基因菌株与同时携带SHV、TEM基因菌株对头孢他啶、头孢曲松及头孢噻肟的耐药率差异有统计学意义 (χ2值分别为7.01、9.93、11.01,P均＜0.05);携带单一SHV基因菌株与同时携带SHV、OXA基因菌株对头孢他啶、头孢曲松及头孢噻肟的耐药率有统计学差异 (χ2值分别为14.11、17.58、11.54,P均＜0.05);携带CTX-M基因菌株与同时携带SHV、CTX-M基因菌株对头孢他啶耐药率差异有统计学意义(χ2=23.61,P＜0.05);携带TEM基因菌株与同时携带SHV、TEM基因菌株对头孢他啶耐药率差异有统计学意义(P=0.01).结论 肺炎克雷伯菌产ESBL逐年增加,以SHV型为主,携带CTX-M型ESBL基因菌株逐年增多.

Abstract：

Objective To analyze the antibiotic susceptibility, ESBL genotype of clinical Klebsiella pneumoniae strains isolated from People′s hospital and facilitate the control of resistance spread. Methods Identification and antibiotic susceptibility tests of 1 205 strains from 2001 to 2007 were done by VITEK-2 system.The antibiotic susceptibility results were analyzed by whonet5.3.The ESBL gene was detected by PCR and the Chi-square test was used for statistical analysis.Results The rate of ESBL-producing strains in klebsiella pneumoniae has increased from 2001 to 2007[18.8% (40/213) in 2001, 20.9% (53/253) in 2002, 32.8% (42/128) in 2003, 33.6% (45/137) in 2004, 36.6% (60/164) in 2005, 45.3% (68/150) in 2006 and 45.6% (73/160) in 2007].The SHV gene was the most dominant in ESBL genotypes.There were 83.3% (50/60) ESBL strains in 2005 with SHV gene, 82.3%(56/68) in 2006 and 83.6%(61/73) in 2007.The rated of strains with CTX-M gene were increasing.There were 26.7%(16/60) ESBL strains with CTX-M gene in 2005, 36.7%(25/68) in 2006 and 54.8%(40/73) in 2007.The isolates with more than one type of ESBL gene were increasing.There were 45%(27/60) ESBL strains in 2005 with two types of ESBL gene, and no one had more than two types of ESBL gene in that year.There were 47.9%(35/73) ESBL strains in 2007 with two types of ESBL gene.In 2007 there were 9.6%(7/73) and 2.7%(2/73) ESBL strains with three types and four types of ESBL gene respectively.There was a statistical difference between the antibiotic resistance rates of cefotaxime, ceftriaxone and ceftazidime in SHV-gene-phore strains (χ2=13.22, P＜0.01).The strains with SHV gene were more resistant to cefotaxime than ceftriaxone and ceftazidime.There also was a statistical difference of the antibiotic resistance rate of cefotaxime, ceftriaxone and ceftazidime between strains with TEM gene (χ2=9.91, P＜0.01) and CTX-M gene (χ2=34.84, P＜0.01) respectively.None of the strains with CTX-M gene was sensitive to cefotaxime, and they were more resistant to ceftriaxone than ceftazidime.The strains with TEM gene were more resistant to cefotaxime than ceftriaxone and ceftazidime.There were statistical differences of the antibiotic resistance rate to cefotaxime (χ2=29.65, P＜0.01), ceftriaxone (χ2=20.26, P＜0.01) and ceftazidime (χ2=20.26, P＜0.01) between the strains with SHV gene only and strains with SHV and CTX-M gene concurrently.There were also statistical differences of the antibiotic resistance rates to cefotaxime (χ2=11.01, P＜0.01), ceftriaxone (χ2=9.93, P＜0.01) and ceftazidime (χ2=7.01, P＜0.01) between the strains with SHV gene only and strains with SHV and TEM gene concurrently.The antibiotic resistance rates to cefotaxime (χ2=11.54, P＜0.01), ceftriaxone (χ2=17.58, P＜0.01) and ceftazidime (χ2=14.11, P＜0.01) were statistically different between the strains with SHV gene only and strains with SHV and OXA gene concurrently.The antibiotic resistance rates to ceftazidime (χ2=23.61, P＜0.01) were statistically different between the strains with CTX-M gene only and strains with SHV and CTX-M gene concurrently. There was no statistical difference in antibiotic resistance rates to cefotaxime (χ2=3.55, P＜0.01) and ceftriaxone (χ2=3.35, P＜0.01) between the strains with CTX-M gene only and strains with SHV and CTX-M gene concurrently. The antibiotic resistance rates to ceftazidime (P=0.01) were statistically different between the strains with only TEM gene and strains with SHV and TEM gene concurrently, and there was no statistical difference of the antibiotic resistance rates to cefotaxime (P=0.29) and ceftriaxone (P=0.26) between the strains with TEM gene only and strains with SHV and TEM gene concurrently. ConclusionsThe producing rate of ESBL is increasing year after year and the SHV type of ESBL is the dominant one.Strains with more than one type of ESBL gene are increasing.The antibiotic resistance rates to cefotaxime, ceftriaxone and ceftazidime are statistically different between strains with same ESBL genotype.     

云南省德宏和昆明地区高效抗逆转录病毒治疗后HIV-1流行毒株pol区基因变异分析

Objective To investigate the variations in the pol region of HIV-1 strain in treatment failed patients in Yunnan province's Dehong prefecture and Kunming. Methods Blood samples were collected from 139 patients who experienced treatment failure ( HAART treatment ＞ 1 years and HIV-1 RNA Viral load ＞ 1 000 copies/ml). HIV-1 RNA was extracted from plasma, and nested-PCR was performed for amplification of PR and RT genes on the HIV-1 pol region. The PCR products were then sequenced and submitted to Stanford HIV Drug Resistance Database for comparison. The evolution tree was built up with MEGA 4. 1 system, combined with patients' demographics. Results The most prevalent mutation in Kunming patients were T215F/N/Y/I, M41L/M, and T69G/N/I/S/A/D, the mutation rates were 39%(24/62), 27% (17/62) and 27% (17/62) , respectively, which were higher than the corresponding mutations in the Dehong prefecture [16% ( 11/69), 13% (9/69) and 9% (6/69)]. The rate differences were statistically significant ( x2 = 8.646, 4.242 and 7. 909, all P ＜ 0.05 ). The most common HIV-1 pol region subtype in the Dehong patients were CRF01_AE subtype (32%, 22/69), followed by C subtype (25% ,17/69), and B subtype ( 19%, 13/69). Major subtypes in Kunming patients were 08_BC (60%,37/62 ), CRF01_AE subtype(21% , 13/62 ) and 07_BC ( 15% ,9/62). Conclusions Partial differences of the point mutations of the HIV-1 strain pol region and frequency of their occurrences exist among Dehong and Kunming patients, HIV-1 strains in Dehong prefecture for the NNRTIs mutations at the T215 Y/N/T, M41L and T69G/N/I/S/A/D are significantly higher than those in Kunming. Six isoforms are found respectively:CRF01_AE, B, C, BC, 08_BC and 07_BC from the epidemic strains of HIV-1 pol region subtype in Dehong and Kunming areas.     

云南省德宏和昆明地区高效抗逆转录病毒治疗后HIV-1流行毒株pol区基因变异分析

Objective To investigate the variations in the pol region of HIV-1 strain in treatment failed patients in Yunnan province's Dehong prefecture and Kunming. Methods Blood samples were collected from 139 patients who experienced treatment failure ( HAART treatment ＞ 1 years and HIV-1 RNA Viral load ＞ 1 000 copies/ml). HIV-1 RNA was extracted from plasma, and nested-PCR was performed for amplification of PR and RT genes on the HIV-1 pol region. The PCR products were then sequenced and submitted to Stanford HIV Drug Resistance Database for comparison. The evolution tree was built up with MEGA 4. 1 system, combined with patients' demographics. Results The most prevalent mutation in Kunming patients were T215F/N/Y/I, M41L/M, and T69G/N/I/S/A/D, the mutation rates were 39%(24/62), 27% (17/62) and 27% (17/62) , respectively, which were higher than the corresponding mutations in the Dehong prefecture [16% ( 11/69), 13% (9/69) and 9% (6/69)]. The rate differences were statistically significant ( x2 = 8.646, 4.242 and 7. 909, all P ＜ 0.05 ). The most common HIV-1 pol region subtype in the Dehong patients were CRF01_AE subtype (32%, 22/69), followed by C subtype (25% ,17/69), and B subtype ( 19%, 13/69). Major subtypes in Kunming patients were 08_BC (60%,37/62 ), CRF01_AE subtype(21% , 13/62 ) and 07_BC ( 15% ,9/62). Conclusions Partial differences of the point mutations of the HIV-1 strain pol region and frequency of their occurrences exist among Dehong and Kunming patients, HIV-1 strains in Dehong prefecture for the NNRTIs mutations at the T215 Y/N/T, M41L and T69G/N/I/S/A/D are significantly higher than those in Kunming. Six isoforms are found respectively:CRF01_AE, B, C, BC, 08_BC and 07_BC from the epidemic strains of HIV-1 pol region subtype in Dehong and Kunming areas.     

深圳社区感染沙门菌耐药基因调查与同源性分析

目的 调查深圳社区感染沙门菌耐药特点和分子机制,并进行同源性分析.方法 收集深圳市人民医院2002——2007年临床分离沙门菌共93株,PCR和DNA测序分析沙门菌gyrA、gyrB、parC和parE基因QRDR的突变,PCR检测质粒介导喹诺酮耐药基因qnr和aac(6')-Ib-cr,β内酰胺酶基因blaTEM、blaSHV、blaOXA和blaCTX-M基因,以及Ⅰ类整合子,PFGE对沙门菌进行分子分型.结果 伤寒沙门菌和甲型副伤寒沙门菌对氨苄西林、氯霉素、复方磺胺甲噁唑、头孢曲松和环丙沙尾敏感率为96%～100%;52%(13/25)伤寒沙门菌和95%(61/64)甲型副伤寒沙门菌对萘啶酸耐药.24%(6/25)萘啶酸耐药伤寒沙门菌和94%(60/64)萘啶酸耐药甲型副伤寒沙门菌对环丙沙星敏感性降低(MIC 0.125～μg/ml).75株萘啶酸耐药环丙沙星敏感沙门菌仅GyrA的QRDR均存在第83位或87位单个氨基酸替代,其中Ser83Phe突变占91%(68/75).2株环丙沙星耐药沙门菌在QRDR中均携带GyrA上2个点突变和parC上1个点突变.93株沙门菌均未发现质粒介导的qnr和aac(6')-Ib-cr 基因.1株头孢曲松耐药甲型副伤寒沙门菌检测到blaCTX-M-14基因,且该基因上游存在插入序列ISEcpl.3株多重耐药沙门菌均存在一个1 900 bp的Ⅰ类整合子,其基因盒均为dhfrⅫ-orfF-aadA2,同时携带blaTEM-1或blaOXA-30基因.25株伤寒沙门菌共有22种不同的PFGE带型,64株甲型副伤寒沙门菌的PFGE带型平均相似性为91%.90例患者均系社区感染,6例甲型副伤寒患者发病前30天内曾前往外地旅行.结论 深圳社区感染伤寒和甲型副伤寒沙门菌对萘啶酸耐药率较高,沙门菌GyrA的QRDR点突变是萘啶酸耐药的重要机制,甲型副伤寒沙门菌菌株间遗传同源性极高,来自同一克隆.

Abstract：

Objective To investigate the antimicrobial resistance mechanisms and genetic homogeny of Salmonella from community acquired infections in Shenzhen,China.Methods Ninety-three of Salmonella were isolated from 2002 to 2007 at Shenzhen People's Hospital,China.PCR and DNA sequencing were used to investigate the mutation in QRDR of the gyrA,gyrB,parC and parE.Plasmid mediated quinolone resistance genes including qnr and aac(6')-Ib-cr,β-lactamase genes including blaTEM,blaSHV,blaOXA, blaCTX-M, and class 1 integron were detected. All isolates were typed by PFGE. Results S. enterica typhi and S. enterica paratyphi A were susceptible to ampicillin, chloramphenicol, trimethoprim/sulfamethoxazole, ceftriaxone and ciprofloxacin, with the susceptible rate of 96%-100%. Fifty-two percent (13/25) of S. enterica typhi and 95% (61/64) of S. enterica paratyphi A were resistant to nalidixic acid. Twenty-four percent (6/25) of nalidixic acid-resistant S. enterica typhi and 94% (60/64) of nalidixic acid-resistant S. enterica paratyphi A showed decreased susceptibility to ciprofloxacin (MIC of 0. 125-1 μg/ml).All nalidixic acid-resistant (susceptible to ciprofloxacin ) Salmonella (NARS) isolates had a single substitution in the QRDR of GyrA, and 91% (68/75) of these isolates carried the substitution Ser83Phe in GyrA. Two mutations in the QRDR of GyrA were detected in both of two ciprnfloxacin-resistant Salmonella,with the additional one mutation in the QRDR of parC. Plasmid mediated quinolone resistance genes including qnr and aac(6')-lb-cr were not detected in any isolate. The blaCTX-M-14 gene was detected in a ceftriaxoneresistant isolate of S. enterica paratyphi A, with ISEcpl located on the upstream of it. Three muhidrugresistant strains of Salmonella all carried one 1 900 bp classⅠ integron gene cassette dhfrⅫ-orfF-aadA2,with the additional one β-lactamase gene of blaTEM-1, or blaOXA-30. Twenty-two distinct PFGE patterns were observed among twenty-five S. enterica typhi. The PFGE patterns of sixty-four S. enterica paratyphi A showed limited genetic diversity (average similarity of 91% ). Ninety investigated inpatients were infected in the community. Six patients infected by S. enterica paratyphi A had a travel history before infection. Conclusions Nalidixic acid-resistant S. enterica typhi and S. enterica paratyphi A are highly prevalent in Shenzhen,China. The mutation in the QRDR of GyrA is the prevalent mechanism responsible for the resistance to nalidixic acid in Slmonella. The great genetic similarity among S. enterica paratyphi A isolates indicates endemic disease from the presence of a single clone over 6-year period.     

多重耐药鲍曼不动杆菌对替加环素耐药状况分析

目的 了解多重耐药鲍曼不动杆菌对临床常用抗生素及新药替加环素的耐药状况.方法 收集2008-2009年浙江省4所教学医院的602株临床分离鲍曼不动杆菌,采用琼脂稀释法检测其对13种临床常用抗生素的敏感性,以及对多黏菌素B和替加环素的敏感性.同时,采用PFGE技术对24株多重耐药鲍曼不动杆菌进行同源性分析,以确定菌株间的亲缘关系.结果 浙江省4家教学医院2008-2009年分离的鲍曼不动杆菌主要来自于呼吸道标本,2009年达到277株(86.0%),血液标本数量从2008年的15株(5.4%)下降到2009年的5株(1.5%),而其他标本无明显变化.鲍曼不动杆菌对临床常用的13种抗生素均有不同程度的耐药,耐药率35.0%～85.0%.与2008年相比,除左氧氟沙星和妥布霉素耐药率分别下降0.9%和9.0%以外,2009年其余抗生素耐药率均有不同程度地上升,头孢曲松和头孢吡肟耐药率增加了近10.0%,对碳青霉烯类抗生素亚胺培南和美罗培南的耐药率分别达到74.2%(239/602)和70.8%(228/602).鲍曼不动杆菌对替加环素显示了很高的耐药率,耐药率达到78.9%(475/602),而多黏菌素B耐药率仅为3.7%(22/602).PFGE分型显示2008-2009年24株鲍曼不动杆菌有6个克隆型,其中A型最常见,占50%.结论 鲍曼不动杆菌对替加环素的耐药加大了院内感染控制的难度,临床应加强控制,防止多重耐药菌的传播.

Abstract：

Objective To investigate the resistance of Acinetobacter baumannii to clinical common antibiotics and new drug tigecycline. Methods Six hundred and two Acinetobacter baumannii isolates were collected from 2008 to 2009 in four teaching hospitals in Zhejiang province. Agar dilution method was used to detect the resistance of 13 clinical commom antibiotics, polymyxin B and tigecycline. Homology analysis of 24 multi-drug resistant Acinetobacter baumannii strains was used to investigate the relationship of each strain with the method of pulsed field gel electrophoresis. Results From 2008 to 2009, the Acinetobacter baumannii isolates of four teaching hospitals in Zhejiang province were mainly isolated from respiratory specimens with the number of 277 (86.0%) strains in 2009, the number of blood samples decreased from 15 (5.4%) strains in 2008 to 5 ( 1.5% ) strains in 2009, and there were no obvious change in other specimens. Acinetobacter baumannii strains were resistant to 13 clinical common antibiotics at different degree, fluctuated from 35.0% to 85.0%. Compared with the resistance in 2008, levofloxacin and tobramyxin decreased 0. 9% and 9.0% in 2009, respectively. However, the resistance of other antibiotics increased at different degree, the resistance of ceftriaxone and cefepime increased about 10.0%, and the resistance of imipenem and meropenem increased to 74.2% (239/602) and 70.8% (228/602) in 2009,respectively. Acinetobacter baumannii showed high resistance to tigecycline with the percent of 78.9% (475/602), while it was only 3.7% (22/602) for polymyxin B. There were six cloning types among the 24 Acinetobacter baumannii isolates, and the most common type was type A with the percent of 50%.Conclusions The resistance of tigecycline makes the situation of nosocomial infectious more serious. It is necessary to control the transmission of multi-drug resistant Acinetobacter baumannii immediately.     

结核分枝杆菌耐利福平和异烟肼相关基因快速检测的应用研究

目的 利用DNA芯片检测技术直接检测痰标本中结核分枝杆菌耐利福平(RFP)、异烟肼(INH)相关的耐药基因(rpoB、katG/inhA),评价DNA芯片检测技术临床应用的可行性.方法 对586份涂阳痰标本使用L-J培养并用终点法确定其耐药性,同时利用DNA芯片检测技术检测痰标觋本中结核分枝杆菌的rpoB、katG/inhA常见基因突变位点的突变情况,比对两种方法的检测结果,对不符合的菌株测定其相应DNA序列,评估上述试验的准确性.结果 (1)586份涂阳痰标本,其中3(+)163份、2(+)204份、1(+)217份,培养阳性584份.耐药结果显示,对INH、RFP敏感的菌株分别为361株和327株,耐药菌株分别为223株和247株,其中低浓度耐药、高浓度敏感菌株分别为93株和59株,低浓度、高浓度均耐药菌株分别为130株和188株.(2)耐药基因特异性片段扩增阳性标本367份(62.8%)、阴性217份(37.2%).对INH耐药相关基因(katG/inhA)突变检出率是28.4%,突发发生位点集中在katG315位密码子(89.8%);对RFP耐药相关基因(rpoB)突变检出率是55.9%(137/247),突变发生位点主要在rpoB 531和rpoB 526位密码子,发生率分别是68.6%和16.1%.(3)对L-J药敏结果与DNA芯片检测结果不符的菌株进行DNA序列分析,发现有漏检现象.结论 DNA芯片技术直接检测样本中结核分枝杆菌的相关耐药基因存在可行性,如直接应用于临床样本检测,关键要解决样本中DNA的提取效率、PCR的扩增效率和试验的质量控制.     

等位基因特异性PCR法快速检测结核分枝杆菌常见耐药突变基因

摘要：目的：建立一套同步检测结核分枝杆菌(MTB)常见耐药突变基因的等位基因特异性PCR（AS-PCR）检测体系,以间接判断对利福平（RFP）与异烟肼（INH）的耐药性。 方法：用AS-PCR技术同步检测58株MTB临床分离株rpoB基因516位、526位和531位,katG基因315位及inhA基因-15位密码子突变,并与DNA测序结果进行比对。 结果：AS-PCR法对RFP耐药株检出率为95.1%（39/41）,其中rpoB基因531位、526位、516位点突变分别检出28株、10株、2株,包括531位与526位联合点突变1株;未检出突变的2株RFP耐药株经测序验证1株未发生突变、1株发生533位点突变;RFP敏感株均未检测到突变。AS-PCR法对INH耐药株检出率为86.5%（45/52）,其中katG基因315位点突变43株、inhA基因-15位点突变2株,未检出突变的7株INH耐药株经测序验证未见突变;INH敏感株均未检测到突变。 结论：等位基因特异性PCR能够快速检测MTB常见突变基因,具有较高的敏感性与特异性,快速经济、操作简便。     

结核杆菌异烟肼表型耐药与katG基因突变相关性研究

目的:探讨结核分支杆菌异烟肼(INH)表型耐药与KatG基因密码子315位和463位基因改变的相关性。方法:采用基因直接测序法对结核分支杆菌分离株KatG基因进行分析。结果:132株异烟肼耐药菌株中68株KatG基因密码子315位有基因突变,突变率51.52%(68/132),野生型密码子315AGC(Ser)突变成ACC(Thr)60株,AAC(Asn)6株,ACA(Thr)1株,GGC(GIy)1株。133株INH敏感菌株未发现KatG 315位基因突变。132株INH耐药菌株中123株KatG基因密码子463位有基因突变,突变率为93.18%,野生型密码子463CGG(Arg)突变成CTG(Leu)123株;133株敏感菌株中114株KatG基因密码子463位有基因突变,突变率为85.71%,野生型密码子463 CGG(Arg)突变成CTG(Leu)114株。结论:①KatG基因315位密码子突变是菌株异烟肼表型耐药的重要分子基础,以Ser315Thr错义突变为主。②KatG基因463位密码子突变与异烟肼耐药表型没有相关性,不是结核杆菌异烟肼耐药的分子标志。该位点突变可能是基因多态性,与结核菌治疗带来的选择性压力无关。     

Molecular characterization of isoniazid-resistant Mycobacterium tuberculosis isolates collected in Australia

Elucidation of the molecular basis of isoniazid (INH) resistance in Mycobacterium tuberculosis has led to the development of different genotypic approaches for the rapid detection of INH resistance in clinical isolates. Mutations in katG, in particular the S315T substitution, are responsible for INH resistance in a large proportion of tuberculosis cases. However, the frequency of the katG S315T substitution varies with population samples. In this study, 52 epidemiologically unrelated clinical INH-resistant M. tuberculosis isolates collected in Australia were screened for mutations at katG codon 315 and the fabG1-inhA regulatory region. Importantly, 52 INH-sensitive isolates, selected to reflect the geographic and genotypic diversity of the isolates, were also included for comparison. The katG S315T substitution and fabG1-inhA -15 C-to-T mutation were identified in 34 and 13 of the 52 INH-resistant isolates, respectively, and none of the INH-sensitive isolates. Three novel katG mutations, D117A, M257I, and G491C, were identified in three INH-resistant strains with a wild-type katG codon 315, fabG1-inhA regulatory region, and inhA structural gene. When analyzed for possible associations between resistance mechanisms, resistance phenotype, and genotypic groups, it was found that neither the katG S315T nor fabG1-inhA -15 C-to-T mutation clustered with any one genotypic group, but that the -15 C-to-T substitution was associated with isolates with intermediate INH resistance and isolates coresistant to ethionamide. In total, 90.4% of unrelated INH-resistant isolates could be identified by analysis of just two loci: katG315 and the fabG1-inhA regulatory region.     

Molecular analysis of isoniazid resistance in Mycobacterium tuberculosis isolates recovered from South Korea

The katG, inhA and ahpC genes, in 71 isoniazid (INH)-resistant and 26 INH-susceptible Mycobacterium tuberculosis isolates, from South Korea were examined by sequencing and MspI restriction enzyme analysis. Mutations in the katG 315 alone, katG 315 plus inhA, katG 315 plus ahpC, katG 309 alone, katG 309 plus inhA, inhA alone, and ahpC alone, were detected in 54.9, 2.8, 1.4, 1.4, 1.4, 19.7, and 5.6% of the 71 INH-resistant isolates, respectively. There was no statistically significant difference (p > 0.05) in the frequencies of these mutations for the INH-monoresistant compared with the multidrug-resistant isolates. Mutations in the katG codon 315 were associated with the high-level of INH resistance (MIC, >1 microg/ml), whereas the mutation in the inhA promoter region was associated with the low-level of INH resistance (MIC, >0.2 to 1 microg/ml). The previously undescribed GGT-->GAT (Gly-->Asp) mutation in the katG codon 309 was found in two rifampin, including-multidrug-resistant isolates, but we cannot assess if this is predictive of INH resistance. The sensitivity and specificity of molecular analysis of the katG codon 315 and/or the inhA promoter region were 80.3 and 100%, respectively. Therefore, mutations in these regions are highly predictive of INH resistance in South Korea.     

Molecular analysis of katG gene mutations in strains of Mycobacterium tuberculosis complex from Africa.

A sample of 124 isoniazid (INH)-resistant and 88 susceptible strains of Mycobacterium tuberculosis complex from south, central, and west Africa was analyzed by direct sequence analysis and PCR-restriction fragment length polymorphism analysis of their catalase-peroxidase (katG) genes. Point mutations at codon 315 were found in the genomes of 64% of INH-resistant strains, but no complete deletions were identified. Mutations at codon 463 were independent of INH resistance and were linked to the geographic origins of the strains.     

Phenotypic and molecular characterization of Mycobacterium tuberculosis isolates resistant to both isoniazid and ethambutol

In performing radiometric susceptibility testing on over 2,000 patient isolates of Mycobacterium tuberculosis during the past 6 years, we found that resistance to 7.5 microg/ml ethambutol (EMB) occurred only in isolates that are also resistant to 0.4 microg/ml isoniazid (INH). Using 157 selected isolates in the present study, we performed radiometric and agar proportion susceptibility tests and DNA sequencing of genetic regions associated with resistance to these two drugs. The goal was to study the occurrence of the common mutations associated with resistance to each drug and also to determine whether any particular INH-resistance-associated mutation occurred more often in combination with any particular EMB-resistance-associated mutation. In an analysis of 128 isolates resistant to 0.4 microg/ml INH, we found that a mutation at katG Ser315 was more common in isolates also resistant to 7.5 microg/ml EMB (61 of 67=91.0%) than in isolates either susceptible to EMB or resistant to 2.5 microg/ml EMB (39 of 60=65.0%). These observations suggest that INH-resistant strains with a mutation at katG Ser315 are more likely to acquire resistance to 7.5 microg/ml EMB than are isolates with INH-resistance-associated mutations at other sites. In addition, we found that 64 of 67 (95.5%) isolates resistant to 7.5 microg/ml EMB contained a mutation in either codon 306 or codon 406 of embB. Met306Val was the most common embB mutation, present in 52 (77.6%) of the 67 isolates. Most occurrences of this mutation (49 of 52=94.2%) were found in isolates that also contained the katG Ser315Thr mutation. Finally, sequencing this region of embB appears to be sufficiently sensitive for use as a rapid screening tool for detection of high-level resistance to EMB.     

Analysis of the oxyR-ahpC region in isoniazid-resistant and -susceptible Mycobacterium tuberculosis complex organisms recovered from diseased humans and animals in diverse localities.

Automated DNA sequencing was used to analyze the oxyR-ahpC region in 229 Mycobacterium tuberculosis complex isolates recently recovered from diseased humans and animals. The entire 1,221-bp region was studied in 118 isolates, and 111 other isolates were sequenced for oxyR, ahpC, or the 105-bp oxyR-ahpC intergenic region. The sample included isoniazid (INH)-susceptible and -resistant organisms in which the katG gene and inhA locus had previously been sequenced in their entirety to identify polymorphisms. A total of 16 polymorphic sites was identified, including 5 located in oxyR, 2 in ahpC, and 9 in the 105-bp intergenic region. All polymorphic sites located in the intergenic region, and the two missense substitutions identified in ahpC, occurred in INH-resistant organisms. In contrast, there was no preferential association of polymorphisms in oxyR, a pseudogene, with INH-resistant organisms. Surprisingly, most INH-resistant strains with KatG codon 315 substitutions that substantially reduce catalase-peroxidase activity and confer high MICs of INH lacked alterations in the ahpC gene or oxyR-ahpC intervening region. Taken together, the data are consistent with the hypothesis that some polymorphisms located in the ahpC-oxyR intergenic region are selected for after reduction in catalase or peroxidase activity attributable to katG alterations arising with INH therapy. These mutations are uncommon in recently recovered clinically significant organisms, and hence, there is no strict association with INH-resistant patient isolates. The ahpC compensatory mutations are apparently uncommon because strains with a KatG null phenotype are relatively rare among epidemiologically independent INH-resistant organisms.     

结核分枝杆菌katG、inhA、ahpC等突变与异烟肼耐药关系的研究

目的：了解结核分枝杆菌katG、inhA、ahpC、fabG1、sodA及sodC基因突变的特征及其与耐异烟肼的关系。方法对127例活动性肺结核患者痰标本进行菌型鉴定及结核分枝杆菌药敏试验,提取结核分枝杆菌菌株DNA,应用PCR扩增katG、inhA及ahpC、fabG1、sodA及sodC基因片段,并进行DNA序列分析。结果结核分枝杆菌药物敏感试验显示127株结核分枝杆菌中,其中47株耐异烟肼,80株对异烟肼敏感,耐异烟肼率为37.01%。47株耐异烟肼中,29株存在katG和（或）inhA基因突变,其中22株（46.81%,22/47）存在katG基因单位点突变,3株（6.38%,3/47）存在inhA基因单位点突变,4株（8.51%,4/47）存在katG及inhA基因联合位点突变。22株katG基因单位点突变中,20株为AGC315ACC、AGC315AAC （42.55%,20/47）突变,2株（2.13%,1/47）分别为CTG378CCG（Leu378Pro）、ACG394ATG（Thr394Met）突变,该突变位点及突变形式尚未见文献报道。18株katG及inhA未突变结核分枝杆菌均未检测到ahpC、fabG1、sodA及sodC基因突变。结论结核分枝杆菌对异烟肼耐药主要与katG和inhA基因突变有关。耐异烟肼结核分枝杆菌临床分离株378和394新突变位点的发现为进一步研究耐药机制以及耐药结核病的快速检测提供了依据。     

聚合酶链反应-测序技术快速检测耐异烟肼结核分枝杆菌KatG基因突变的研究

目的应用PCR-DNA测序技术快速检测耐异烟肼结核分枝杆菌分离株KatG基因突变,评价其在检测结核分枝杆菌异烟肼耐药性方面的应用价值。方法47株耐异烟肼结核分枝杆菌临床分离株及30株结核分枝杆菌敏感分离株用PCR-DNA测序技术检测KatG基因突变。结果47株耐异烟肼结核分枝杆菌分离株中,有31株KatG基因检出有突变,突变检出率为66.0%(31/47);30株结核分枝杆菌敏感株检出1株KatG基因突变。结论PCR-DNA测序技术方法敏感、准确、特异,可快速检测结核分枝杆菌KatG耐药基因突变,有利于耐异烟肼结核分枝杆菌耐药性的快速检测。     

Single nucleotide polymorphisms in genes associated with isoniazid resistance in Mycobacterium tuberculosis

Isoniazid (INH) is a central component of drug regimens used worldwide to treat tuberculosis. Previous studies have identified resistance-associated mutations in katG, inhA, kasA, ndh, and the oxyR-ahpC intergenic region. DNA microarray-based experiments have shown that INH induces several genes in Mycobacterium tuberculosis that encode proteins physiologically relevant to the drug's mode of action. To gain further insight into the molecular genetic basis of INH resistance, 20 genes implicated in INH resistance were sequenced for INH resistance-associated mutations. Thirty-eight INH-monoresistant clinical isolates and 86 INH-susceptible isolates of M. tuberculosis were obtained from the Texas Department of Health and the Houston Tuberculosis Initiative. Epidemiologic independence was established for all isolates by IS6110 restriction fragment length polymorphism analysis. Susceptible isolates were matched with resistant isolates by molecular genetic group and IS6110 profiles. Spoligotyping was done with isolates with five or fewer IS6110 copies. A major genetic group was established on the basis of the polymorphisms in katG codon 463 and gyrA codon 95. MICs were determined by the E-test. Semiquantitative catalase assays were performed with isolates with mutations in the katG gene. When the 20 genes were sequenced, it was found that 17 (44.7%) INH-resistant isolates had a single-locus, resistance-associated mutation in the katG, mabA, or Rv1772 gene. Seventeen (44.7%) INH-resistant isolates had resistance-associated mutations in two or more genes, and 76% of all INH-resistant isolates had a mutation in the katG gene. Mutations were also identified in the fadE24, Rv1592c, Rv1772, Rv0340, and iniBAC genes, recently shown by DNA-based microarray experiments to be upregulated in response to INH. In general, the MICs were higher for isolates with mutations in katG and the isolates had reduced catalase activities. The results show that a variety of single nucleotide polymorphisms in multiple genes are found exclusively in INH-resistant clinical isolates. These genes either are involved in mycolic acid biosynthesis or are overexpressed as a response to the buildup or cellular toxicity of INH.     

High prevalence of KatG Ser315Thr substitution among isoniazid-resistant Mycobacterium tuberculosis clinical isolates from northwestern Russia, 1996 to 2001

A total of 204 isoniazid (INH)-resistant strains of Mycobacterium tuberculosis isolated from different patients in the northwestern region of Russia from 1996 to 2001 were screened by a PCR-restriction fragment length polymorphism (RFLP) assay. This assay uses HapII cleavage of an amplified fragment of the katG gene to detect the transversion 315AGC-->ACC (Ser-->Thr), which is associated with INH resistance. This analysis revealed a 93.6% prevalence of the katG S315T mutation in strains from patients with both newly and previously diagnosed cases of tuberculosis (TB). This mutation was not found in any of 57 INH-susceptible isolates included in the study. The specificity of the assay was 100%; all isolates that contained the S315T mutation were classified as resistant by a culture-based susceptibility testing method. The Beijing genotype, defined by IS6110-RFLP analysis and the spacer oligonucleotide typing (spoligotyping) method, was found in 60.3% of the INH-resistant strains studied. The katG S315T shift was more prevalent among Beijing genotype strains than among non-Beijing genotype strains: 97.8 versus 84.6%, respectively, for all isolates, including those from patients with new and previously diagnosed cases, isolated from 1999 to 2001 and 100.0 versus 86.5%, respectively, for isolates from patients with new cases isolated from 1996 to 2001. The design of this PCR-RFLP assay allows the rapid and unambiguous identification of the katG 315ACC mutant allele. The simplicity of the assay permits its implementation into routine practice in clinical microbiology laboratories in regions with a high incidence of TB where this mutation is predominant, including northwestern Russia.