Bacteriological follow-up of pulmonary tuberculosis treatment: a study with a simple colorimetric assay.
The viability of Mycobacterium tuberculosis (MTB) in serial sputum specimens from persistently smear positive patients was evaluated. The assay was based on oxidation-reduction of Alamar Blue and Malachite Green dyes that change their color in response to MTB growth. A total of 280 sputum specimens from 40 persistently smear positive TB patients and 40 sputa from non-tuberculosis patients were digested, decontaminated and examined microscopically. To check the MTB viability, the sediments from decontaminated samples were inoculated into three culture media: Lowenstein-Jensen (LJ) slants, Alamar Blue and Malachite Green culture tubes. We found that out of 280 smear positive specimens, the LJ culture was positive in 124 (44%). The numbers of correctly identified S+/C+ cases by Alamar Blue and Malachite Green were 118 (95%) and 116 (93%), respectively. The mean time required for reporting the positive signal in Alamar Blue culture tubes was 9 versus 11 days by Malachite Green culture tubes. In the standard LJ culture media the average detection time was 27 days (P < 0.05). The sensitivity of LJ was 99%, Alamar Blue 95% and Malachite Green 93%. The specificity was 100%, 92% and 93%, respectively. The oxidation-reduction method is rapid, sensitive and inexpensive in monitoring the treatment response of patients with pulmonary TB. Thus, using this method can be of paramount importance, particularly in resource-constrained areas.
Farnia
Parissa
P
Iranian National reference TB Laboratory, National Research Institute of Tuberculosis and Lung Disease (NRITLD), Shaheed Beheshti University of Medical Sciences and Health Services, Darabad, Tehran 19556, Iran. pfarnia@hotmail.com
Mohammadi
Foroozan
F
Mirsaedi
Mehdi
M
Zia Zarifi
Abolhasan
A
Tabatabee
Javad
J
Bahadori
Moslem
M
Akbar Velayati
Ali
A
Reza Masjedi
Mohammad
M
D000995:Antitubercular Agents / Q000627:therapeutic use; D001431:Bacteriological Techniques; D003124:Colorimetry / Q000379:methods*; D005500:Follow-Up Studies; D006801:Humans; D008853:Microscopy; D009169:Mycobacterium tuberculosis / Q000166:cytology / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism; D010078:Oxazines / Q000378:metabolism; D010084:Oxidation-Reduction; D012394:Rosaniline Dyes / Q000378:metabolism; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D013997:Time Factors; D016896:Treatment Outcome; D014397:Tuberculosis, Pulmonary / Q000188:drug therapy* / Q000382:microbiology*; D014966:Xanthenes / Q000378:metabolism
D000995:Antitubercular Agents; D010078:Oxazines; D012394:Rosaniline Dyes; D014966:Xanthenes; C005095:malachite green; C005843:resazurin