title: Evaluation of a microcolony detection method and phage assay for rapid detection of Mycobacterium tuberculosis in sputum samples.
abstract: Early and rapid diagnosis of tuberculosis is necessary for both treatment and control of the disease. This study evaluated two microcolony observation techniques based on liquid and solid media and a mycobacteriophage assay, to evaluate their effectiveness in the diagnosis of pulmonary TB compared with a standard culture (BACTEC 460 and LJ medium). Middlebrook7H9 (M7H9) broth based on microcolony determination detected 57/61 positives cultures (n = 200) with a sensitivity of 93.4% and a specificity of 87.1%. M7H11 agar detected 57/62 positive cultures (n = 198) with a sensitivity of 91.9% and a specificity of 89.7%. The mycobacteriophage assay detected 98/143 (68.5%) of positive samples. The time to positivity was 48 hours in the mycobacteriophage assay versus 7 days in both the M7H9 broth and M7H11 agar. The costs in comparison with the culture (BACTEC 460 and LJ) were 33% and 48% for the microcolony and mycobacteriophage methods, respectively. Microcolony methods were rapid and cost effective compared to standard cultures. The mycobacteriophage assay, despite its lower sensitivity, has a short turn around time, and may be recommended as a screening test in countries with a low prevalence of tuberculosis.
authors.affiliation: Department of Pathology and Microbiology, Aga Khan University, Karachi, Pakistan. seema.irfan@aku.edu
authors.forename: Seema
authors.initials: S
authors.lastname: Irfan
authors.forename: Rumina
authors.initials: R
authors.lastname: Hasan
authors.forename: Akber
authors.initials: A
authors.lastname: Kanji
authors.forename: Qaiser
authors.initials: Q
authors.lastname: Hassan
authors.forename: Iqbal
authors.initials: I
authors.lastname: Azam
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods*; D001681:Biological Assay; D015169:Colony Count, Microbial; D006801:Humans; D009160:Mycobacteriophages / Q000145:classification; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D013183:Sputum / Q000382:microbiology*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000382:microbiology