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  • Oral presentation
  • Open Access

Evaluation of the mycobacteriophage amplification assay for detection of physically and physiologically stressed mycobacterial cells in vitro

  • 1Email author,
  • 1,
  • 1 and
  • 2
BMC Infectious Diseases201414(Suppl 3):O19

https://doi.org/10.1186/1471-2334-14-S3-O19

Published: 27 May 2014

Keywords

  • Tuberculosis
  • Mycobacterium Tuberculosis
  • Stressed Cell
  • Nutrient Starvation
  • Mycobacterium Smegmatis

Background

Currently used laboratory detection methods for Mycobacterium tuberculosis are either slow or low in sensitivity, and therefore there is a need for a more reliable and rapid method. This study was done to evaluate the efficiency of the mycobacteriophage amplification assay in detecting mycobacterial cells that were exposed to the stresses (desiccation, UV radiation, and nutrient starvation) that simulate those in tuberculous droplet nuclei.

Methods

Exponential-phase Mycobacterium smegmatis (non-pathogenic surrogate model for M. tuberculosis) cells were exposed to a particular stressor and then subjected to the phage and colony-forming unit (CFU) assays; the numbers of plaque-forming unit (PFU) and CFU yielded were then compared to those for the unexposed control. We also investigated the effects of treating stressed cells with culture supernatants (containing resuscitation-promoting factors) on their phage infectivity and culturability on solid medium.

Results

Only desiccation and UV exposure decreased PFU significantly (~5x106 to 5x105 PFU/mL and 7.7x106 to 3.4x106 PFU/mL, respectively), whereas all three stressors affected culturability by approximately ten folds (106-108 to 105-107 CFU/mL). These suggest that most stressors affect the culturability of mycobacterial cells more than their phage infectivity. With prior culture supernatant treatment, only desiccated cells showed improved PFU and CFU yields (1.5x106 to 3.1x106 PFU/mL and 4.4x106 to 5.8x106 CFU/mL, respectively).

Conclusion

Hence, there is preliminary evidence that the phage assay might be superior to culture for detection of stressed mycobacterial cells that are in the non-culturable but viable state, and prior resuscitation of stressed cells could potentially improve the assay sensitivity.

Authors’ Affiliations

(1)
Department of Biological Science, Faculty of Science, Universiti Tunku Abdul Rahman, Kampar, Perak, Malaysia
(2)
Department of Biomedical Science, Faculty of Science, Universiti Tunku Abdul Rahman, Kampar, Perak, Malaysia

Copyright

© Cheah et al; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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