BACTEC MGIT 960用于结核分枝杆菌直接药敏试验的研究

目的探讨BACTEC MGIT 960系统在结核分枝杆菌直接药敏试验的临床应用价值。方法对200株临床涂阳痰标本应用BACTEC MGIT 960系统进行一线抗结核药（链霉素、异烟肼、利福平、乙胺丁醇）结核分枝杆菌直接药敏试验,并与同步进行的BACTEC MGIT 960间接药敏试验及传统改良罗氏（L-J）比例法药敏试验进行比较,从结果报告时间和符合率等方面进行评价。统计学分析分别采用配对资料的t检验和Kappa检验。结果 BACTEC MGIT960直接药敏试验报告时间为（9.7±3.1）d,与BACTEC MGIT 960间接药敏试验报告时间（17.5±6.6）d比较差异有统计学意义（t=14.7,P〈0.01）,与L-J法报告时间（50.4±8.6）d比较差异有统计学意义（t=73.4,P〈0.01）;4种一线抗结核药物链霉素、异烟肼、利福平、乙胺丁醇药敏BACTEC MGIT 960直接法与BACTEC MGIT 960间接法药敏结果总符合率为97.3%,BACTEC MGIT 960直接法与L-J法药敏结果总符合率为96.2%。结论 BACTEC MGIT 960直接药敏试验快速、准确,可用于结核分枝杆菌的药物敏感性检测,利于耐药结核病的早期诊断和治疗。     

MGIT 960系统行二线抗结核药物敏感性试验的实用性评价

目的 评价全自动BACTEC MGIT 960系统在结核分枝杆菌二线抗结核药物（second-line anti-TB drugs,SLD）药敏试验中的实用性。 方法 本实验纳入患者435例。该纳入患者均通过痰涂片抗酸染色（萋-尼法）镜检,L-J固体和MGIT 960系统液体培养及鉴定,共筛查出阳性菌株212例。212例阳性菌株分别进行一线抗结核药物异烟肼（INH）、利福平（RFP）、链霉素（S）和乙胺丁醇（EMB）的耐药性试验,其中耐药菌株（所有耐药株）118例。以118例耐药株作为SLD药敏试验实验株,应用L-J和MGIT 960两种方法分别进行卷曲霉素（Cm）、卡那霉素（Km）、氧氟沙星（Ofx）和乙硫异烟胺（Eto）的药物敏感性试验,并计算出两方法药敏试验所需的时间和符合率;L-J和MGIT960两种培养方法的比较采用配对设计的卡方检验;两种方法检测结果的一致性用Kappa值检验判别。 结果 MGIT 960系统药敏试验所需时间平均10.0 d（1183/118）,L-J固体培养法所需时间平均28.5 d（3360/118）,两者相差18.5 d。MGIT 960与L-J培养法的SLD Cm、Km、Ofx和Eto敏感及耐药符合率和一致性检验Kappa值分别为88.1%（104/118）和0.520;95.8%（113/118）和0.815;91.5%（108/118）和0.824;71.2%（84/118）和0.375。 结论 MGIT 960系统液体培养法常用SLD药敏试验与金标准（L-J培养）比较除Eto外符合率高、一致性好;该方法检测快速、准确,具有很强的实用性,可作为结核分枝杆菌快速培养和药敏试验的新方法。     

手工MGIT法检测结核分枝杆菌异烟肼和利福平耐药的效果评价

目的 评价MGIT手工荧光判读法在检测结核分枝杆菌耐药的基层应用价值。方法 以常规L-J比例法为参照方法,比较分析手工荧光MGIT液体药敏法检测300株临床结核分离株异烟肼和利福平药敏效果。结果 手工MGIT液体药敏法检测异烟肼和利福平灵敏度和特异度分别为94.7%和92.6%、95.6%和98.8%。两种药敏方法的异烟肼符合率95.7%,利福平符合率97.7%,两种方法检测异烟肼和利福平敏感性的差异无统计学意义(P>0.05)。液体药敏阳性报告时间平均7.6 d,比传统比例法报告时间提前20.4 d。结论 手工MGIT液体药敏法与常规L-J比例法检测异烟肼和利福平敏感性结果一致性高,能快速、准确检测结核分枝杆菌异烟肼和利福平耐药,适合基层推广。     

微孔板法在一线抗结核药物敏感性试验中的应用价值

目的 分析微孔板法在一线抗结核药物药物敏感性试验(简称“药敏试验”)中的应用价值。方法 收集2019年1—6月西安市胸科医院经BACTEC MGIT 960液体培养(简称MGIT 960法)培养阳性的1086份标本,选择其中经菌种鉴定为结核分枝杆菌且同时对链霉素、异烟肼、利福平、乙胺丁醇行MGIT 960 法和微孔板法药敏试验的331份菌液,分析两种试验方法的检测情况;并以MGIT 960法为标准,评估微孔板法药敏试验的检测效能,对结果不一致的菌液以熔解曲线法检测耐药基因予以核实。结果 以MGIT 960法为标准,微孔板法对链霉素、异烟肼、利福平、乙胺丁醇等4种药品的敏感度、特异度、Kappa值分别为88.7%(63/71)、100.0%(260/260)、0.93,93.9%(77/82)、98.8%(246/249)、0.94,93.8%(45/48)、99.6%(282/283)、0.95,66.7%(14/21)、99.0%(307/310)、0.72。微孔板法与MGIT 960法检测4种药品耐药性结果不一致者分别为链霉素10份、异烟肼8份、利福平6份、乙胺丁醇16份。经熔解曲线耐药基因分析后,结果显示微孔板法为中敏、MGIT 960法为耐药者10份(3.0%,10/331),耐药基因检测结果均为突变,分别为链霉素2份、利福平2份、乙胺丁醇6份;而微孔板法为中敏、MGIT 960法为敏感仅乙胺丁醇1份(0.3%,1/331),耐药基因检测结果为突变;微孔板法为敏感、MGIT 960法为耐药者23份(6.9%,23/331),耐药基因检测结果为野生型10份(分别为链霉素6份、异烟肼4份)、突变型13份(分别为链霉素2份、异烟肼1份、利福平3份、乙胺丁醇7份);微孔板法为耐药、MGIT 960法为敏感者6份(1.8%,6/331),耐药基因检测结果为野生型3份(分别为异烟肼、利福平、乙胺丁醇各1份)、突变型3份(分别为异烟肼2份、乙胺丁醇1份)。结论 微孔板法对一线抗结核药物的耐药性检测操作简便,与MGIT 960法一致性高,且可检测出低浓度耐药情况,可作为临床选择药物及使用剂量时的参考。     

MGIT960与罗氏培养法在结核分枝杆菌培养及药敏试验中的比对分析

目的 比对全自动Bactec MGIT960（MGIT960）系统与改良罗氏（L-J）培养方法 2者在结核分枝杆菌培养、鉴定及药敏试验中的优越性。 方法 按国家疾病预防控制中心（CDC）-碧迪项目辽宁工作方案要求和国际标准WS288-2009《肺结核诊断标准》纳入临床病例。本实验共纳入病例435例,其中男性319例,女性116例,平均年龄52.3岁（10～86岁）。上述每份病例标本均分别进行痰液涂片抗酸染色（萋-尼法）镜检,L-J固体培养和MGIT960系统液体培养。培养阳性者分别进行一线药物异烟肼（INH）、利福平（RIF）、链霉素（STR）和乙胺丁醇（EMB）的L-J法药敏试验（比例法）和MGIT960药敏试验;分别计算出抗酸染色镜检与MGIT960和L-J培养的符合率; L-J培养和MGIT960培养阳性检出率;L-J和MGIT960两种培养方法药敏试验所需的培养时间及符合率等。 结果MGIT960培养法和L-J培养法与痰涂片镜检的阳性符合率分别为90.8%（187/206）和89.3%（184/206）;MGIT960与L-J结果符合率92.8%（219/236）;MGIT960和L-J平均培养时间分别为9.5 d和31.5 d;MGIT960和L-J一线药物INH、RIF、STR和EMB敏感性试验的符合率分别为92.7%、95.9%、91.8%和97.3%。 结论 全自动MGIT960系统培养方法的敏感度和特异度高于L-J培养法,报告时间平均缩短至9.5-d,该系统是目前最为理想的快速结核分枝杆菌培养、鉴定和药敏试验检测系统。     

MicroDST~(TM)微孔板检测法对抗结核一、二线药物敏感性试验的临床价值

目的评价MicroDST~(TM)微孔板药敏(简称微孔药敏)检测法对结核分枝杆菌对一、二线抗结核药物敏感性试验的临床价值。方法采用随机数字表法选取BACTEC MGIT 960快速培养法培养的201株并经鉴定为结核分枝杆菌的分离株,采用微孔药敏法对一、二线抗结核药物,包括链霉素(SM)、异烟肼(INH)、利福平(RFP)、乙胺丁醇(EMB)、阿米卡星(AM)、卷曲霉素(CM)、左氧氟沙星(LFX)、莫西沙星(MFX)、对氨基水杨酸(PAS)、丙硫异烟胺(PTO)对分离株进行药物敏感性检测,并将其结果与罗氏比例法药敏检测结果进行比较分析,评价两种方法的符合率。结果 201株结核分枝杆菌临床分离株用微孔药敏法进行药敏检测的结果判读时间为7～14 d,其结果与"金标准"的罗氏比例法药敏的结果比较,微孔药敏检测的敏感性均不低于80%,且链霉素(SM)、异烟肼(INH)、乙胺丁醇(EMB)、利福平(RFP)、左氧氟沙星(LFX)、莫西沙星(MFX)、阿米卡星(AM)、卷曲霉素(CM)、对氨基水杨酸(PAS)、丙硫异烟胺(PTO)、的符合率分别为96.2%、92.2%、92.2%、93.8%、85.7%、94.1%、93.3%、84.6%、94.1%、100%。结论微孔药敏方法检测MTB对一、二线抗结核药物敏感性的检测结果与罗氏比例法检测的药敏结果具有较高的一致性,且检测快速,易于推广,符合了当前结核病的诊断需求。     

微量MIC法和罗氏比例法对结核分枝杆菌药敏检测比对分析

目的评价微量液体培养基最低抑菌浓度(MIC)法和比例法在结核分枝杆菌药敏试验中的临床应用价值,确定一种快速准确的药敏试验方法。方法收集经菌种鉴定为结核分枝杆菌的菌株,采用微量MIC法和比例法对一线抗结核药物异烟肼(H)、利福平(R)、乙胺丁醇(E)和二线抗结核药物卡那霉素(Km)、氧氟沙星(Ofx)、卷曲霉素(Cm)进行药物敏感性试验,采用Kappa检验比较两种方法的一致性。结果 102株结核分枝杆菌经微量MIC法和比例法进行药物敏感性检测,符合率均在80%以上,以比例法为金标准,微量MIC法的灵敏度和特异度分别是INH 91. 11%和96. 49%,RFP 100%和95. 38%,EMB 69. 56%和94. 94%,KM 100%和89. 77%,OFX 76. 47%和92. 94%,CPM 47. 16%和90. 59%。结论微量MIC法和比例法对结核分枝杆菌药敏检测结果除了CPM外均具有较好的一致性,可以为结核患者一、二线药敏检测提供快速有效且廉价的诊断方法。     

结核分枝杆菌L型的诱导及其对抗菌药物的敏感性

目的：观察异烟肼、利福平、乙胺丁醇抗结核药物诱导形成结核分支杆菌L型以及结核分支杆菌L型对抗菌药物敏感性。方法将结核分支杆菌接种于含有不同质量浓度利福平（0．05、0．1、0．2μg/mL）、异烟肼（0．01、0．04、0．08μg/mL）、乙胺丁醇（1、2．5、5μg/mL）的BD960液体培养基内,10 d后在显微镜下观察结核分支杆菌L型的形成情况。培养结核分支杆菌L型,在显微镜高倍镜下观察,并检测其对抗菌药物的敏感性。结果0．1、0．2μg/mL利福平,0．04、0．08μg/mL异烟肼,2．5、5μg/mL乙胺丁醇可诱导形成结核分支杆菌L型。在含有4μg/mL链霉素、0．2μg/mL异烟肼、40μg/mL利福平、2μg/mL乙胺丁醇、1μg/mL对氨基水杨酸的非高渗培养基内培养7 d后均可见结核分枝杆菌L型生长,而含有30μg/mL卡那霉素、40μg/mL卷曲霉素、3μg/mL氧氟沙星的培养基内未见其生长。结论中高浓度的利福平、异烟肼、乙胺丁醇能够诱导结核分支杆菌L型形成。结核分枝杆菌L型对卡那霉素、卷曲霉素、氧氟沙星敏感。     

70例MDR-TB病例抗结核二线药物敏感性检测结果分析

了解耐多药结核分枝杆菌临床分离株对二线药物耐药情况,评价BACTEC MGIT960系统在抗结核二线药敏试验中的临床应用价值。方法 收集本院的痰培养阳性、经菌种鉴定和一线药物的药物敏感性试验确定为耐多药的结核分枝杆菌菌株。采用BACTEC MGIT960对4种二线药氧氟沙星（OFLX）、左氧氟沙星（LVFX）、阿米卡星（AMK）和卷曲霉素（CPM）进行药物敏感性检测,并与改良 L-J罗氏培养法相比较。结果 (1)2008年10月-2009年4月,70例MDR-TB分离到的菌株,包括初治病例26例、复治病例44例,对四种药的总耐药率为61.4%（43/70）。对OFLX、LVFX、AMK和CPM耐药率分别为48.6%、40.0%、17.1%、7.1%。初治耐药率为57.7%（15/26）,复治耐药率达63.6%（28/44）。符合XDR-TB诊断者5例（7.1%）,包括初治者1例（1.4%）,复治者4例（5.7%）。（2）BACTEC MGIT960二线药物敏感试验与改良L-J法相比,平均报告时间仅10.2天,明显短于L-J法,符合率在90%以上。结论 （1） 在住院耐多药结核病患者中对这四种抗结核二线药物的耐药率已经到了一个较高水平;同时,当地存在XDR-TB,应该引起重视。（2）BACTEC MGIT960系统可以准确而快速地检测结核分枝杆菌对二线药物的耐受性.     

中国耐多药结核分枝杆菌二线抗结核药物敏感性分析

目的分析中国耐多药结核分枝杆菌（MDR-TB）菌株对二线抗结核药物的敏感性,为耐多药结核病防治政策的制定提供科学依据。方法从全国2007-2008年耐药基线调查收集的菌株中选取2008年4-7月期间耐药基线调查点收集的126株MDR菌株,对其进行2种一线抗结核药物（链霉素和乙胺丁醇）和7种二线抗结核药物（氧氟沙星、卡那霉素、卷曲霉素、乙硫异烟胺、丙硫异烟胺、环丝氨酸和对氨基水杨酸）的敏感性进行检测,分析对不同药物耐药率以及交叉耐药的情况。结果一线药物链霉素和乙胺丁醇,总体耐药率分别为73.0%（92/126）和58.7%（74/126）;对于二线药物,氧氟沙星和乙硫异烟胺耐药率最高,分别为25.4%（32/126）和23.0%（29/126）;其次为卡那霉素和环丝氨酸,其耐药率分别为17.5%（22/126）和13.5%（17/126）;最后为卷曲霉素、丙硫异烟胺和对氨基水杨酸,其耐药率均为3.2%（4/126）。初治患者对卡那霉素（χ²=20.025,P<0.01）和环丝氨酸（χ²=6.558,P=0.017）的耐药率(卡那霉素: 20/60, 33.3%; 环丝氨酸: 13/60,21.7%)显著高于复治患者(卡那霉素: 2/66, 3.0%; 环丝氨酸: 4/66,6.1%)。此外,卡那霉素和卷曲霉素,乙硫异烟胺和丙硫异烟胺间均存在单向交叉耐药,在对卷曲霉素耐药的4株中,有3株同时对卡那霉素耐药;4株对丙硫异烟胺耐药菌株均同时对乙硫异烟胺耐药。结论我国耐多药结核分枝杆菌菌株对二线抗结核药物具有较高的耐药率,特别是氧氟沙星和乙硫异烟胺,这对我国结核病控制工作,特别是耐多药结核病控制工作的实施带来严峻的挑战。     

Evaluation of Mycobacteria Growth Indicator Tube (MGIT) for drug susceptibility testing of Mycobacterium tuberculosis.

SETTING: Mycobacteria Supranational Reference Laboratory. OBJECTIVE: To evaluate the Mycobacteria Growth Indicator Tube (MGIT) method for drug susceptibility testing of Mycobacterium tuberculosis. DESIGN: One hundred and one clinical strains of M. tuberculosis were evaluated for their susceptibilities to isoniazid (INH), rifampicin (RIF), ethambutol (EMB) and streptomycin (SM) by MGIT and by the proportion method on L?wenstein-Jensen (L-J) medium. The concentrations of drugs in MGIT were: 0.1, 1.0, 3.5 and 0.8 microg/ml for INH, RIF, EMB and SM, respectively. RESULTS: The results for individual drugs showed a good correlation: the specificity was 100% for INH, RIF and EMB and 92% for SM; the sensitivity was 100%, 94.6%, 96.1% and 89.7% for INH, RIF, EMB and SM, respectively, and the accuracy values 1.0, 0.98, 0.99 and 0.91. CONCLUSION: The MGIT system appears to be a reliable and simple non-radiometric method for the drug susceptibility testing of M. tuberculosis.     

四种结核分枝杆菌检测方法临床诊断效能的评价

目的 评估痰涂片抗酸染色镜检(简称“涂片法”)、L-J培养基(Lowenstein-Jenden medium)固体培养(简称“L-J法”)、BACTEC MGIT 960液体培养(简称“MGIT 960法”)及GeneXpert MTB/RIF(简称“GeneXpert法”)等4种结核分枝杆菌检测方法检出结核病病原菌的能力。方法 搜集2018年1月1日至2018年12月31日北京结核病控制研究所451例疑似肺结核患者的痰标本,同时使用涂片法、L-J法、MGIT 960法及GeneXpert法进行检测。对上述4种方法的检测结果以临床诊断情况(总体分为“肺结核患者”与“非肺结核患者”)为参考标准,计算各种检测方法的敏感度、特异度、阳性预测值、阴性预测值、一致率;同时计算4种方法联合检测结果的病原学阳性率(其中任何一种方法检测结果为阳性,即判断为联合检测结果为阳性)。结果 451例疑似肺结核患者中,临床最终诊断依据《WS 288—2017肺结核诊断》标准进行,诊断为肺结核患者227例(肺结核225例、肺结核并发结核性胸膜炎2例),非肺结核患者224例[非结核分枝杆菌(NTM)肺病11例,陈旧性肺结核6例,肺部阴影待查181例,胸腔积液3例,肺纤维化1例,肺炎3例,肺癌1例,密切接触者筛查18例]。以临床诊断结果为参考标准,涂片法、L-J法、GeneXpert法、MGIT 960法检测敏感度分别为22.5%(51/227)、32.2%(73/227)、37.9%(86/227)、43.2%(98/227),特异度分别为96.0%(215/224)、96.4%(216/224)、100.0%(224/224)、95.1%(213/224),一致率分别为59.0%(266/451)、64.1%(289/451)、68.7%(310/451)、69.0%(311/451)。涂片法和L-J法联合检测,以及涂片法、L-J法和GeneXpert法联合检测,4种方法联合检测的敏感度分别为34.8%(79/227)、43.6%(99/227)、49.8%(113/227),特异度分别为96.0%(215/224)、96.0%(215/224)、93.8%(210/224),一致率分别为65.2%(294/451)、69.6%(314/451)、71.6%(323/451)。结论 以临床诊断为参考标准,MGIT 960法检测的敏感度最高;GeneXpert法检测的特异度最高;4种方法联合检测能够显著提高诊断敏感度,与临床诊断的一致率也显著提高。     

Evaluation of the BACTEC MGIT 960 system for drug susceptibility testing of Mycobacterium tuberculosis isolates compared with the proportion method on solid media]

The methods most widely used for susceptibility testing against anti-tuberculosis drug (AST) are the proportion method on L?wenstein-Jensen egg (L-J), Ogawa egg or Middle-brook agar media, and BACTEC TB 460 system. Recently, drug concentrations have been established for AST using the automated BACTEC MGIT 960 system (aMGIT). We have evaluated the BACTEC MGIT 960 SIRE kit for AST of Mycobacterium tuberculosis to isoniazid, rifampin, streptomycin and ethambutol. Also we compared the results with the proportion methods on Middlebrook 7H10 agar (7H10), L-J and Ogawa egg, and the manual MGIT system (mMGIT). Overall concordance rates among aMGIT and the proportion method on 7H10 or Ogawa media were 98.3% and 96.9% for 4 first-line drugs, respectively. Rates were particularly high for isoniazid and rifampin between aMGIT and 7H10 (efficiency of 100%). On the other hand, overall concordance rates among two egg media, L-J and Ogawa were 99.9%. Agreement between aMGIT and mMGIT was high for the AST to isoniazid and rifampin, but lower for the AST to ethambutol (90.9%), which relates to a lower specificity of mMGIT. The mean times to aMGIT and mMGIT results of susceptibility were 7 and 6 days, respectively, contrasted with 3 weeks in 7H10 and 4 weeks in L-J and Ogawa, indicating that both MGIT systems have the potential to consistently meet the turnaround time suggested by Centers for Disease Control and Prevention (CDC) of the United States. These results demonstrate that the fully automated BACTEC MGIT 960 SIRE system for AST is useful for rapid diagnosis of drug resistant tuberculosis.     

Susceptibility testing to second-line drugs and ethambutol by Genotype MTBDRsl and Bactec MGIT 960 comparing with agar proportion method

The incidence of multidrug-resistant tuberculosis (MDRTB) is increasing. Rapid detection of resistance to second-line drugs is essential for patient management and efficient control of tuberculosis. The aim of the present study was to assess the ability of the GenoType MTBDRsl DNA strip and the Bactec MGIT 960 assay to detect resistance to second-line drugs and ethambutol in multidrug-resistant clinical isolates using the agar proportion method as a reference technique. Twenty-six Mycobacterium tuberculosis complex isolates identified as multidrug-resistant on the basis of conventional drug susceptibility testing were retrieved from our laboratory archive (1992-2010) for evaluation. The susceptibility of these strains to second-line drugs and ethambutol was tested prospectively using MGIT 960 and GenoType MTBDRsl. The turnaround time for agar proportion, MGIT 960, and GenoType MTBDRsl were, respectively, 21 days, 8 days, and 8?h. Sensitivity values for MGIT 960 and GenoType MTBDRsl were, respectively, ethambutol (85.7, 28.6%), amikacin (50, 75%), and ofloxacin (50, 83.3%). Specificity values were, respectively, ethambutol (73.7, 89.5%), amikacin (72.7, 95.5%), and ofloxacin (100, 100%). Our data show that both methods have significant limitations and cannot replace conventional drug susceptibility testing. The results of resistance testing should be interpreted with caution and confirmed using the reference method.     

骨关节结核各类标本进行结核分枝杆菌培养与PCR检测的阳性率结果分析

目的 比较骨关节结核病灶中脓液、干酪、肉芽及死骨组织的结核分枝杆菌培养阳性率,及结核分枝杆菌BACTEC MGIT 960（简称“MGIT 960”）培养、改良罗氏培养基培养、PCR检测的联合阳性率.方法 2011年6月至2012年5月首都医科大学附属北京胸科医院收治的经病理明确诊断为骨关节结核的患者50例,通过手术获取病灶中的脓液（50份）、干酪（42份）、肉芽（48份）及死骨组织标本（43份）,分别进行结核分枝杆菌MGIT 960培养及改良罗氏培养基培养,比较4种组织标本的培养阳性率,计算2种培养方法的联合阳性率;对脓液标本单独通过PCR方法进行了阳性率检测;计算脓液标本3种方法的联合阳性率.结果 4种标本MGIT 960培养的阳性率依次为：死骨组织（41.9％,18/43）＞脓液（40.0％,20/50）＞肉芽（33.3％,16/48）=干酪（33.3 ％,14/42）;4种标本改良罗氏培养阳性率依次为：肉芽（20.8％,10/48）＞脓液（20.0％,10/50）＞死骨组织（16.3 ％,7/43）＞干酪（14.3％,6/42）;脓液的PCR检测阳性率为48.0％（24/50）.MGIT 960和改良罗氏培养2种结核分枝杆菌培养方法的联合阳性率为50.0％（25/50）,而PCR检测、MGIT960和改良罗氏培养3种方法的联合阳性率为68.0（34/50）.结论 骨关节结核患者,应尽可能选择多种标本以提高培养阳性率.MGIT 960培养可以作为首选的细菌学诊断方法,但如果再联合使用改良罗氏培养和PCR扩增技术,能够进一步提高检出阳性率.     

Multicentre evaluation of an automated BACTEC 960 system for susceptibility testing of Mycobacterium tuberculosis.

SETTING: Three mycobacteria reference laboratories in the south-eastern part of Brazil. OBJECTIVE: To evaluate the automated Mycobacteria Growth Indicator Tube (MGIT) for drug susceptibility testing of Mycobacterium tuberculosis. DESIGN: Performance of the automated BACTEC MGIT 960 (M960) system for testing M. tuberculosis susceptibility to streptomycin (SM), isoniazid (INH), rifampicin (RMP) and ethambutol (EMB) was evaluated with 95 clinical isolates and compared to the results of the radiometric BACTEC 460TB (B460) system, the proportion method (PM), and the resistance ratio method (RRM). Judicial susceptibility profiles of 88 isolates were defined based on two or more concordant results among B460, PM and RRM, and used as a reference for comparison with M960 results. RESULTS: Agreement rates between M960 and conventional methods were 95.2% with B460, 96.6% with the PM and 93.4% with the RRM. The lowest agreement rates were obtained for SM with the RRM and for EMB with B460. When comparing M960 with judicial susceptibility profiles, the agreement rate was 97.9%. The agreement rates obtained for INH and RMP were 99.2% and for SM and EMB they were 96.2% and 96.9%, respectively. The mean time to reporting the M960 results was 6.9 days. CONCLUSION: M960 offers great improvements when compared to the proportion and resistance ratio methods and would benefit patient treatment.     

BACTEC MGIT 960 system for drug susceptibility testing of Mycobacterium tuberculosis: a study using external quality assessment strains

OBJECTIVE: To evaluate the performance of the BACTEC MGIT 960 system for drug susceptibility testing (MGIT AST) of Mycobacterium tuberculosis to isoniazid, rifampin, streptomycin and ethambutol. DESIGN: Fifty external quality assessment strains of M. tuberculosis provided by the Coordinating Centers of WHO/ IUATLD were tested by BACTEC MGIT 960 system, and the results were compared with the referee results of the WHO/IUATLD Supranational Reference Laboratory Network (SRLN). RESULTS AND CONCLUSION: Overall concordance rates of the results obtained by MGIT AST and the referee results of the SRLN were 97.3% for four first-line drugs. Agreement rates were particularly high for isoniazid, rifampin, and streptomycin (agreement rate of over 97%), but somewhat lower for ethambutol, which relates to a lower sensitivity of MGIT AST. Turnaround times from inoculation to drug susceptibility results ranged from 6 to 13 days for the MGIT AST system with a median time of 7 days; this contrasted with three weeks for the proportion method using Middlebrook 7H10 agar, indicating that MGIT AST system has the potential to consistently meet with the turnaround time guidelines suggested by the Centers for Disease Control and Prevention of the United States. These results demonstrate that the fully automated BACTEC MGIT 960 AST system is useful for the rapid diagnosis of drug resistant tuberculosis.