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Evaluation of bleach-sedimentation for sterilising and concentrating Mycobacterium tuberculosis in sputum specimens

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dc.contributor.author Chew, R.
dc.contributor.author Calderón, C.
dc.contributor.author Schumacher, S.G.
dc.contributor.author Sherman, J.M.
dc.contributor.author Caviedes, L.
dc.contributor.author Fuentes, P.
dc.contributor.author Coronel, J.
dc.contributor.author Valencia, T.
dc.contributor.author Hererra, B.
dc.contributor.author Zimic-Peralta, Mirko Juan
dc.contributor.author Huaroto, L.
dc.contributor.author Sabogal, I.
dc.contributor.author Escombe, A.R.
dc.contributor.author Gilman, Robert Hugh
dc.contributor.author Evans, Carlton Anthony William
dc.date.accessioned 2022-01-18T19:34:35Z
dc.date.available 2022-01-18T19:34:35Z
dc.date.issued 2011
dc.identifier.uri https://hdl.handle.net/20.500.12866/11037
dc.description.abstract Background: Bleach-sedimentation may improve microscopy for diagnosing tuberculosis by sterilising sputum and concentrating Mycobacterium tuberculosis. We studied gravity bleach-sedimentation effects on safety, sensitivity, speed and reliability of smear-microscopy.Methods: This blinded, controlled study used sputum specimens (n = 72) from tuberculosis patients. Bleach concentrations and exposure times required to sterilise sputum (n = 31) were determined. In the light of these results, the performance of 5 gravity bleach-sedimentation techniques that sterilise sputum specimens (n = 16) were compared. The best-performing of these bleach-sedimentation techniques involved adding 1 volume of 5% bleach to 1 volume of sputum, shaking for 10-minutes, diluting in 8 volumes distilled water and sedimenting overnight before microscopy. This technique was further evaluated by comparing numbers of visible acid-fast bacilli, slide-reading speed and reliability for triplicate smears before versus after bleach-sedimentation of sputum specimens (n = 25). Triplicate smears were made to increase precision and were stained using the Ziehl-Neelsen method.Results: M. tuberculosis in sputum was successfully sterilised by adding equal volumes of 15% bleach for 1-minute, 6% for 5-minutes or 3% for 20-minutes. Bleach-sedimentation significantly decreased the number of acid-fast bacilli visualised compared with conventional smears (geometric mean of acid-fast bacilli per 100 microscopy fields 166, 95%CI 68-406, versus 346, 95%CI 139-862, respectively; p = 0.02). Bleach-sedimentation diluted paucibacillary specimens less than specimens with higher concentrations of visible acid-fast bacilli (p = 0.02). Smears made from bleach-sedimented sputum were read more rapidly than conventional smears (9.6 versus 11.2 minutes, respectively, p = 0.03). Counting conventional acid-fast bacilli had high reliability (inter-observer agreement, r = 0.991) that was significantly reduced (p = 0.03) by bleach-sedimentation (to r = 0.707) because occasional strongly positive bleach-sedimented smears were misread as negative.Conclusions: Gravity bleach-sedimentation improved laboratory safety by sterilising sputum but decreased the concentration of acid-fast bacilli visible on microscopy, especially for sputum specimens containing high concentrations of M. tuberculosis. Bleach-sedimentation allowed examination of more of each specimen in the time available but decreased the inter-observer reliability with which slides were read. Thus bleach-sedimentation effects vary depending upon specimen characteristics and whether microscopy was done for a specified time, or until a specified number of microscopy fields had been read. These findings provide an explanation for the contradictory results of previous studies. en_US
dc.language.iso eng
dc.publisher BioMed Central
dc.relation.ispartofseries BMC Infectious Diseases
dc.rights info:eu-repo/semantics/restrictedAccess
dc.rights.uri https://creativecommons.org/licenses/by-nc-nd/4.0/deed.es
dc.subject Humans en_US
dc.subject comparative study en_US
dc.subject controlled study en_US
dc.subject isolation and purification en_US
dc.subject microbiology en_US
dc.subject evaluation en_US
dc.subject Reproducibility of Results en_US
dc.subject Time Factors en_US
dc.subject drug effect en_US
dc.subject Microscopy en_US
dc.subject Mycobacterium tuberculosis en_US
dc.subject Sensitivity and Specificity en_US
dc.subject Sputum en_US
dc.subject Tuberculosis en_US
dc.subject sensitivity and specificity en_US
dc.subject sputum analysis en_US
dc.subject Bacteriological Techniques en_US
dc.subject microbiological examination en_US
dc.subject diagnostic accuracy en_US
dc.subject intermethod comparison en_US
dc.subject centrifugation en_US
dc.subject microscopy en_US
dc.subject laboratory diagnosis en_US
dc.subject staining en_US
dc.subject Observer Variation en_US
dc.subject reproducibility en_US
dc.subject acid fast bacterium en_US
dc.subject bacterial count en_US
dc.subject bleach sedimentation en_US
dc.subject bleaching agent en_US
dc.subject Centrifugation en_US
dc.subject disinfectant agent en_US
dc.subject Disinfectants en_US
dc.subject Disinfection en_US
dc.subject hypochlorite sodium en_US
dc.subject reliability en_US
dc.subject safety en_US
dc.subject sedimentation en_US
dc.subject Sodium Hypochlorite en_US
dc.subject Specimen Handling en_US
dc.subject technique en_US
dc.subject water en_US
dc.subject Ziehl Neelsen method en_US
dc.title Evaluation of bleach-sedimentation for sterilising and concentrating Mycobacterium tuberculosis in sputum specimens en_US
dc.type info:eu-repo/semantics/article
dc.identifier.doi https://doi.org/10.1186/1471-2334-11-269
dc.subject.ocde https://purl.org/pe-repo/ocde/ford#3.03.08
dc.relation.issn 1471-2334


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