title: Optimizing tuberculosis testing for basic laboratories.
abstract: Optimal tuberculosis testing usually involves sputum centrifugation followed by broth culture. However, centrifuges are biohazardous and scarce in the resource-limited settings where most tuberculosis occurs. To optimize tuberculosis testing for these settings, centrifugation of 111 decontaminated sputum samples was compared with syringe-aspiration through polycarbonate membrane-filters that were then cultured in broth. To reduce the workload of repeated microscopic screening of broth cultures for tuberculosis growth, the colorimetric redox indicator 2,3-diphenyl-5-(2-thienyl) tetrazolium chloride was added to the broth, which enabled naked-eye detection of culture positivity. This combination of filtration and colorimetric growth-detection gave similar results to sputum centrifugation followed by culture microscopy regarding mean colony counts (43 versus 48; P = 0.6), contamination rates (0.9% versus 1.8%; P = 0.3), and sensitivity (94% versus 95%; P = 0.7), suggesting equivalency of the two methods. By obviating centrifugation and repeated microscopic screening of cultures, this approach may constitute a more appropriate technology for rapid and sensitive tuberculosis diagnosis in basic laboratories.
authors.affiliation: Laboratory of Infectious Diseases Research, Department of Microbiology, Faculty of Sciences, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: Eric
authors.initials: E
authors.lastname: Ramos
authors.forename: Samuel G
authors.initials: SG
authors.lastname: Schumacher
authors.forename: Mark
authors.initials: M
authors.lastname: Siedner
authors.forename: Beatriz
authors.initials: B
authors.lastname: Herrera
authors.forename: Willi
authors.initials: W
authors.lastname: Quino
authors.forename: Jessica
authors.initials: J
authors.lastname: Alvarado
authors.forename: Rosario
authors.initials: R
authors.lastname: Montoya
authors.forename: Louis
authors.initials: L
authors.lastname: Grandjean
authors.forename: Laura
authors.initials: L
authors.lastname: Martin
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Sherman
authors.forename: Robert H
authors.initials: RH
authors.lastname: Gilman
authors.forename: Carlton A
authors.initials: CA
authors.lastname: Evans
mesh_terms: D000328:Adult; D000995:Antitubercular Agents / Q000494:pharmacology; D001431:Bacteriological Techniques / Q000379:methods* / Q000592:standards*; D003124:Colorimetry; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D005374:Filtration; D006801:Humans; D007753:Laboratories / Q000592:standards*; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D014376:Tuberculosis / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D000078329:Workforce; D016526:Workload; D055815:Young Adult
chemical_list: D000995:Antitubercular Agents