Performance of Mycobacterium Growth Indicator Tube BACTEC 960 with Lowenstein–Jensen method for diagnosis of Mycobacterium tuberculosis at Ethiopian National Tuberculosis Reference Laboratory, Addis Ababa, Ethiopia

Abstract

BackgroundBacteriological 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.MethodsA 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.ResultsFrom 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.ConclusionsThe 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.

Application value of tissue tuberculosis antigen combined with Xpert MTB/RIF detection in differential diagnoses of intestinal tuberculosis and Crohn’s disease

“…The lower yield of MTBC culture in biopsy specimens might be associated with the culture medium and the number of colonoscopic biopsies.The yield of MTBC culture on the LJ medium was lower than that on the MGIT system. However, the false-positive rates for the MGIT system was higher than those for LJ methods [35] . A recent report showed thatan additional four (total eight) colonoscopic biopsies improved the yield of TB culture positivity over four biopsies by 11.4%-14.3% [34] .…”

Application value of tissue tuberculosis antigen combined with Xpert MTB/RIF detection in differential diagnosis of intestinal tuberculosis and Crohn’s disease

“…Lower yield of AFB culture in biopsy specimens may be associated with culture medium and the number of colonoscopic biopsies.The yield of AFB culture on LJ medium is lower than that on MGIT system. however it should be noted that false-positive rates for MGIT system was higher than LJ methods [34] .In a recently report, additional four (total eight) colonoscopic biopsies improved the yield of TB culture positivity over four biopsies by 11.4% to 14.3% [33] . If for improving AFB culture positivity, Increasing the number of colonoscopic biopsy specimens to eight should be considered,although it cost more time.…”

Diagnostic accuracy of the Xpert MTB/RIF assay for bone and joint tuberculosis: A meta-analysis

“…Nine studies only used BACTEC MGIT 960 liquid culture as the reference, one study only used Lowenstein-Jensen solid culture as the reference [34], and four studies used both of them as references [18,22,24,35]. The performances of BACTEC MGIT 960 liquid and Lowenstein-Jensen solid cultures were different [54], which might also be one of the sources of heterogeneity among the studies. Separate data used in the subgroup of different reference standards were limited; thus, further meta-analysis could not be performed.…”