title: A continuously monitored colorimetric method for detection of Mycobacterium tuberculosis complex in sputum.
abstract: METHODS
  Mbeya, Tanzania.
  
  
  OBJECTIVE
  To develop a new liquid culture method to detect Mycobacterium tuberculosis complex (MTC) in sputum using 2,3-diphenyl-5-thienyl-(2)-tetrazolium (STC), the nitrate reductase assay (NRA) and p-nitrobenzoic acid (PNB).
  
  
  METHODS
  Ninety-three sputum samples collected from 18 tuberculosis patients were decontaminated with N-acetyl-L-cysteine-sodium hydroxide using MGIT™ 960 and in STC-NRA cultures, both in the presence and in the absence of PNB, an inhibitor of MTC growth. The reduction of STC by colour change indicated mycobacterial growth; NRA was then performed to confirm MTC.
  
  
  RESULTS
  STC-NRA culture was positive for acid-fast bacilli in 66/93 (71%) samples, of which 60/93 (64.5%) were identified as MTC-positive and 6/93 (6.5%) as indeterminate mycobacteria. MGIT indicated MTC in 59/93 (63.4%) cultures. Contamination was detected in 12/93 (13%) STC-NRA cultures vs. 29/93 (31.2%) MGIT cultures. The mean time to detection (TTD) of MTC using STC-NRA was 14 days and 7 days using MGIT.
  
  
  CONCLUSIONS
  The STC-NRA method is sensitive for the detection of MTC in sputum. TTD increased with duration of anti-tuberculosis treatment, highlighting the value of this method in monitoring treatment success. The method is simple and inexpensive and, unlike MGIT, does not require technical equipment. The preliminary performance characteristics of the method should be further evaluated in larger studies.
authors.affiliation: National Institute of Medical Research, Mbeya Medical Research Center, Mbeya, Tanzania.
authors.forename: G
authors.initials: G
authors.lastname: Rojas-Ponce
authors.forename: A
authors.initials: A
authors.lastname: Rachow
authors.forename: H
authors.initials: H
authors.lastname: Guerra
authors.forename: D
authors.initials: D
authors.lastname: Mapamba
authors.forename: J
authors.initials: J
authors.lastname: Joseph
authors.forename: R
authors.initials: R
authors.lastname: Mlundi
authors.forename: S
authors.initials: S
authors.lastname: Marimoto
authors.forename: N E
authors.initials: NE
authors.lastname: Ntinginya
authors.forename: C
authors.initials: C
authors.lastname: Mangu
authors.forename: A
authors.initials: A
authors.lastname: Framhein
authors.forename: A
authors.initials: A
authors.lastname: Butler
authors.forename: A
authors.initials: A
authors.lastname: Kohlenberg
authors.forename: D
authors.initials: D
authors.lastname: Ngatemelela
authors.forename: G
authors.initials: G
authors.lastname: Froeschl
authors.forename: L
authors.initials: L
authors.lastname: Maboko
authors.forename: M
authors.initials: M
authors.lastname: Hoelscher
authors.forename: N
authors.initials: N
authors.lastname: Heinrich
mesh_terms: D000995:Antitubercular Agents / Q000627:therapeutic use; D003124:Colorimetry / Q000379:methods*; D016903:Drug Monitoring / Q000379:methods; D005240:Feasibility Studies; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification*; D011237:Predictive Value of Tests; D013183:Sputum / Q000382:microbiology*; D013636:Tanzania; D013997:Time Factors; D016896:Treatment Outcome; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents