title: Use of colorimetric culture methods for detection of Mycobacterium tuberculosis complex isolates from sputum samples in resource-limited settings.
abstract: Despite recent advances, tuberculosis (TB) diagnosis remains imperfect in resource-limited settings due to its complexity and costs, poor sensitivity of available tests, or long times to reporting. We present a report on the use of colorimetric methods, based on the detection of mycobacterial growth using colorimetric indicators, for the detection of Mycobacterium tuberculosis in sputum specimens. We evaluated the nitrate reductase assay (NRA), a modified NRA using para-nitrobenzoic acid (PNB) (NRAp), and the resazurin tube assay using PNB (RETAp) to differentiate tuberculous and nontuberculous mycobacteria. The performances were assessed at days 18 and 28 using mycobacterium growth indicator tube (MGIT) and Löwenstein-Jensen (LJ) medium culture methods as the reference standards. We enrolled 690 adults with suspected pulmonary tuberculosis from a regional referral hospital in Uganda between March 2010 and June 2011. At day 18, the sensitivities and specificities were 84.6% and 90.0% for the NRA, 84.1% and 92.6% for the NRAp, and 71.2% and 99.3% for the RETAp, respectively. At day 28, the sensitivity of the RETAp increased to 82.6%. Among smear-negative patients with suspected TB, sensitivities at day 28 were 64.7% for the NRA, 61.3% for the NRAp, and 50% for the RETAp. Contamination rates were found to be 5.4% for the NRA and 6.7% for the RETAp, compared with 22.1% for LJ medium culture and 20.4% for MGIT culture. The median times to positivity were 10, 7, and 25 days for colorimetric methods, MGIT culture, and LJ medium culture,respectively. Whereas the low specificity of the NRA/NRAp precludes it from being used for TB diagnosis, the RETAp might provide an alternative to LJ medium culture to decrease the time to culture results in resource-poor settings.
authors: Epicentre Mbarara, Mbarara, Uganda. yap.boum@epicentre.msf.org
authors: Yap
authors: Y
authors: Boum
authors: Patrick
authors: P
authors: Orikiriza
authors: Gabriel
authors: G
authors: Rojas-Ponce
authors: Margarita
authors: M
authors: Riera-Montes
authors: Daniel
authors: D
authors: Atwine
authors: Margaret
authors: M
authors: Nansumba
authors: Joel
authors: J
authors: Bazira
authors: Eleanor
authors: E
authors: Tuyakira
authors: Pierre
authors: P
authors: De Beaudrap
authors: Maryline
authors: M
authors: Bonnet
authors: Anne-Laure
authors: AL
authors: Page
mesh_terms: D000328:Adult; D003124:Colorimetry / Q000379:methods*; D003906:Developing Countries; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism; D050901:Nitrate Reductase / Q000378:metabolism; D009579:Nitrobenzoates / Q000378:metabolism; D010078:Oxazines / Q000378:metabolism; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology*; D013997:Time Factors; D014376:Tuberculosis / Q000175:diagnosis* / Q000382:microbiology; D014454:Uganda; D014966:Xanthenes / Q000378:metabolism
chemical_list: D009579:Nitrobenzoates; D010078:Oxazines; D014966:Xanthenes; C005843:resazurin; D050901:Nitrate Reductase; C008629:4-nitrobenzoic acid
references: PLoS One. 2011;6(5):e20175
references: 21655284
references: Antimicrob Agents Chemother. 2002 Aug;46(8):2720-2
references: 12121966
references: PLoS One. 2011 May 09;6(5):e19565
references: 21573015
references: Int J Tuberc Lung Dis. 2004 Dec;8(12):1510-1; author reply 1511
references: 15636501
references: Clin Microbiol Infect. 2007 Aug;13(8):754-62
references: 17378933
references: J Antimicrob Chemother. 2007 Feb;59(2):175-83
references: 17135182
references: Am J Respir Crit Care Med. 2011 Jul 1;184(1):132-40
references: 21493734
references: Int J Tuberc Lung Dis. 2009 Sep;13(9):1112-8
references: 19723400
references: Int J Tuberc Lung Dis. 2010 Feb;14(2):160-4
references: 20074406
references: J Gen Microbiol. 1980 May;118(1):229-34
references: 6775047
references: Future Microbiol. 2007 Apr;2(2):97-101
references: 17661646
references: J Clin Microbiol. 2004 Oct;42(10):4432-7
references: 15472289
references: PLoS One. 2011 Feb 18;6(2):e17214
references: 21364757
references: Lancet Infect Dis. 2006 Oct;6(10):664-74
references: 17008175
references: Cochrane Database Syst Rev. 2013 Jan 31;(2):ED000051
references: 23450616
references: Int J Tuberc Lung Dis. 2000 Feb;4(2):97-107
references: 10694086
references: N Engl J Med. 2010 Sep 9;363(11):1005-15
references: 20825313
references: Int J Tuberc Lung Dis. 2005 Aug;9(8):901-6
references: 16104638
references: Int J Tuberc Lung Dis. 2000 Dec;4(12 Suppl 2):S182-8
references: 11144551
references: J Clin Microbiol. 2008 Oct;46(10):3243-5
references: 18753346
references: J Clin Microbiol. 2002 Feb;40(2):553-5
references: 11825971
references: J Clin Microbiol. 1998 Dec;36(12):3558-66
references: 9817873
references: J Clin Microbiol. 2007 Jul;45(7):2123-5
references: 17475759
references: Int J Tuberc Lung Dis. 2012 Jan;16(1):16-23, i-iii
references: 21986554
references: J Clin Microbiol. 2012 Jul;50(7):2191-3
references: 22518854
references: N Engl J Med. 2006 Oct 12;355(15):1539-50
references: 17035648
references: J Microbiol Methods. 2005 Nov;63(2):145-50
references: 15893391
references: Antimicrob Agents Chemother. 2003 Nov;47(11):3616-9
references: 14576129