Diriba Getu, Kebede Abebaw, Yaregal Zelalem, Getahun Muluwork, Tadesse Mengistu, Meaza Abyot, Dagne Zekarias, Moga Shewki, Dilebo Jibril, Gudena Kebebe, Hassen Mulu, Desta Kassu
Ethiopian Public Health Institute, Addis Ababa, Ethiopia.
School of Laboratory Science, College of Allied Science, Addis Ababa University, Addis Ababa, Ethiopia.
BMC Res Notes. 2017 May 10;10(1):181. doi: 10.1186/s13104-017-2497-9.
Bacteriological confirmed active case detection remains the corner stone for diagnosing tuberculosis. Non-radiometric liquid culture system Mycobacterium Growth Indicator Tube with automated interface had been recommended by expert groups in addition to conventional solid culture media such as Lowenstein-Jensen. However in high burden resource limited countries advanced non-radiometric based tuberculosis diagnostic methods such as MGIT 960 is limited. Therefore we have evaluated the performance of MGIT 960 system compared to LJ for recovery of Mycobacterium complex (MTBC) from clinical specimens.
A cross sectional study was conducted from a total of 908 samples between January 1st, 2013 to December 31st, 2014. Clinical specimens were processed following standard procedures and the final suspension was inoculated to MGIT tubes and LJ slant. Identification and confirmation of MTBC was done by ZN staining and SD Bioline test. Data was analyzed by SPSS version 20. The sensitivity, specificity, recovery rate and the average turnaround time to recover the organism was computed.
From a total of 908 clinical specimens processed using both LJ and BACTEC MGIT liquid culture methods the recovery rate for LJ and MGIT, for smear positive samples was 66.7% (74/111) and 87.4% (97/ 111) respectively while for smear negative samples was 13.4% (108/797) and 17.4% (139/797) for LJ and MGIT methods respectively. The overall recovery rate for MGIT is significantly higher than LJ methods [26% (236/908; vs. 20%, 182/908, P = 0.002)]. The average turnaround time for smear positive samples was 16 and 31 days for MGIT and LJ respectively. Turnaround time for smear negative samples was 20 and 36 days for MGIT and LJ respectively. The overall agreement between MGIT and LJ was fairly good with Kappa value of 0.59 (P < 0.001). In the present study the contamination rate for MGIT is higher than the LJ methods, 15 and 9.3% respectively.
The BACTEC MGIT liquid culture system has better MTBC recovery rate with shorter turnaround time for both smear positive and negative clinical specimens compared to Conventional LJ method. However, efforts should be made in order to reduce the high contamination rate in BACTEC MGIT system and to lesser extent to LJ methods.
细菌学确诊的主动病例检测仍然是诊断结核病的基石。除了传统的固体培养基如罗-琴培养基外，专家小组还推荐了具有自动接口的非放射性液体培养系统分枝杆菌生长指示管。然而，在结核病高负担的资源有限国家，诸如MGIT 960等先进的基于非放射性的结核病诊断方法受到限制。因此，我们评估了MGIT 960系统与罗-琴培养基相比从临床标本中分离结核分枝杆菌复合群（MTBC）的性能。
2013年1月1日至2014年12月31日期间对总共908份样本进行了一项横断面研究。临床标本按照标准程序处理，最终悬液接种到MGIT管和罗-琴斜面上。通过萋-尼染色和SD Bioline试验对MTBC进行鉴定和确认。使用SPSS 20版软件进行数据分析。计算了敏感度、特异度、回收率以及分离出该菌的平均周转时间。
在使用罗-琴培养基和BACTEC MGIT液体培养方法处理的总共908份临床标本中，对于涂片阳性样本，罗-琴培养基和MGIT的回收率分别为66.7%（74/111）和87.4%（97/111），而对于涂片阴性样本，罗-琴培养基和MGIT方法的回收率分别为13.4%（108/797）和17.4%（139/797）。MGIT的总体回收率显著高于罗-琴培养基方法[26%（236/908）；相比之下为20%，182/908，P = 0.002]。涂片阳性样本的MGIT和罗-琴培养基的平均周转时间分别为16天和31天。涂片阴性样本的MGIT和罗-琴培养基的周转时间分别为20天和36天。MGIT和罗-琴培养基之间的总体一致性相当好，Kappa值为0.59（P < 0.001）。在本研究中，MGIT的污染率高于罗-琴培养基方法，分别为15%和9.3%。
与传统的罗-琴培养基方法相比，BACTEC MGIT液体培养系统对于涂片阳性和阴性临床标本均具有更好的MTBC回收率和更短的周转时间。然而，应努力降低BACTEC MGIT系统中的高污染率，并在较小程度上降低罗-琴培养基方法的污染率。
