Improvement in Mycobacterial Yield and Reduced Time to Detection in Pediatric Samples by Use of a Nutrient Broth Growth Supplement

Abstract

There is an urgent need to improve the methods used for the bacteriological diagnosis of childhood mycobacterial disease. This study compared the mycobacterial yields and the times to detection (in days) of mycobacteria in pediatric clinical specimens by using Mycobacterial Growth Indicator Tubes (MGITs) and solid Löwenstein-Jensen (LJ) slants with and without a nutrient broth supplement. A total of 801 specimens from 493 patients were processed: 82.8% were gastric aspirate specimens, 15.6% were sputum specimens, and 1.6% were fine-needle-aspiration biopsy specimens. The mycobacterial yield obtained with MGITs (with and without nutrient broth) was 11.0%, and that obtained with LJ slants was 1.6% (P < 0.001). Of the 88 positive cultures, 62 were detected in MGITs and 73 were detected in MGITs supplemented with nutrient broth (P ‫؍‬ 0.11). The mean time to detection in MGITs (without nutrient broth) was 18.5 days, whereas it was 12.4 days in MGITs with nutrient broth (P < 0.001). Supplementation of standard MGITs improved the mycobacterial yield and significantly reduced the time to detection of mycobacteria in pediatric samples.The accurate diagnosis of childhood tuberculosis remains a major challenge (6, 24), since the paucibacillary nature of the disease in children and the difficulty of specimen collection hamper bacteriological confirmation of the diagnosis. Clinical diagnosis is complicated by the nonspecific symptoms and signs associated with pediatric tuberculosis, particularly in children with human immunodeficiency virus (HIV) infection (3, 9, 14). The traditional growth media used to cultivate mycobacteria include solid egg-based Löwenstein-Jensen (LJ) slants and Middlebrook (7H9) liquid broth-based media, such as that used in the Bactec Mycobacterial Growth Indicator Tube (MGIT) (21, 23).Growth supplements are widely used to improve the culture yield of fastidious organisms (10, 11). For the improved recovery of Mycobacterium bovis BCG, 7H9 broth (glycerol, bovine albumin fraction, glucose, sodium chloride) has been supplemented with Tween 80 (10% polyoxyethylene sorbitan monooleate solution), but the benefits appeared to be limited (7). The Bactec MGIT uses 7H9 broth supplemented with oleic acid, albumin, dextrose, and catalase (OADC) to enhance the growth of mycobacteria (21). The supplementation of 7H9 broth with a nutrient broth (modified Dubos liquid medium) containing beef extract and peptone has been recommended for the enhanced recovery of mycobacteria from inocula containing few organisms (5, 18), but data on its performance in a routine diagnostic laboratory and especially with pediatric specimens are limited. The development of tests that allow the rapid and reliable confirmation of mycobacterial infection in children has been identified as a high research priority (15,17).This study evaluated whether the addition of a meat extractbased growth supplement (Bacto TB nutrient broth; Difco Laboratories Inc., Detroit, MI) to standard culture medium improves the mycobacterial yield and the time to...

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

“…Comparable findings were reported in USA with the rate of 82% for BACTEC MGIT and 76% with LJ method [10]. South African study reported almost similar finding with recovery rate of 83% using BACTEC MGIT for smear positive specimens [11]. …”

Newer Diagnostic Tests for Pulmonary Tuberculosis in Children

“…In addition, MGIT culture had higher sensitivity and specificity (88 vs. 76 %). Similar results in pediatric population were shown by a study from South Africa that compared mycobacterial yield and time to detection of M. tuberculosis in 801 various pediatric specimens (sputum, gastric aspirates and fine needle aspiration) using MGIT and solid LJ [37]. The yield obtained with MGIT was significantly higher than that obtained with LJ (11 vs. 1.6 %), and the time to detection of mycobacteria using MGIT reduced from 26.8 d to 12.4 d. This technique is promising to improve the diagnosis of tuberculosis in children, but is costly, requiring adequate instruments and trained operator.…”

Tuberculosis during the first year of antiretroviral therapy in a South African cohort using an intensive pretreatment screening strategy

“…This is likely to reflect very low mycobacterial numbers in sputum samples and the time to positivity needs to be shortened, for example, by using simple growth supplementation in the culture medium [29]. Availability of novel rapid diagnostic assays for routine screening such as urine lipoarabinomannan detection [17,30] or nucleic acid amplification tests [16] may further expedite diagnosis and treatment initiation and thereby avert some of these deaths.…”