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• Difficulties with a definition of latent mycobacterium tuberculosis infection
  Michael Eisenhut
  Published on: 23 March 2016

• Published on: 23 March 2016

  Difficulties with a definition of latent mycobacterium tuberculosis infection

  • Michael Eisenhut, Consultant Paediatrician

  The authors of a recent article1 reporting on the management of an outbreak of tuberculosis in a crèche in Cork had difficulties with the explanation of what we currently manage as latent M. tuberculosis infection. In their first paragraph they defined “TB” as active pulmonary tuberculosis. Where they reported on communication to the parents of the differences between tuberculosis infection and active disease they menti...

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  The authors of a recent article1 reporting on the management of an outbreak of tuberculosis in a crèche in Cork had difficulties with the explanation of what we currently manage as latent M. tuberculosis infection. In their first paragraph they defined “TB” as active pulmonary tuberculosis. Where they reported on communication to the parents of the differences between tuberculosis infection and active disease they mention that tuberculosis infection implies the presence of “TB” in the body in the absence of diseases manifestations, which is a contradiction. On page 111 the authors claimed that the gold standard for diagnosis of tuberculosis infection is isolation of acid-fast bacilli. Isolation of acid-fast bacilli however does not only mean infection with mycobacteria but presence of active disease with a bacterial load high enough to be detectable.

  The majority of people currently labelled as infected with M. tuberculosis .are labelled as infected on the basis of evidence of an immunological reaction to M. tuberculosis antigen and not on the basis of detection of M. tuberculosis itself. Future studies need to explore markers enabling quantification of extent of the mycobacterial infection. One which has been explored is quantification of neopterin, which is generated by macrophages in response to interferon gamma. It can be measured in urine samples by commercially available assay systems2 . Another approach would be the radio-immuno-scintigraphic detection of specific protein antigens produced only by replicating M. tuberculosis (e.g. Early secretory antigenic target-6 or culture filtrate protein 10) using radio-labelled monoclonal antibodies visualized 3, 4. Such projects could be the first steps towards a more precise definition of latent infection versus active disease and discrimination of latent infection from immunological memory. This could enable design of a more tailored treatment regime and monitoring of its impact on elimination of M. tuberculosis infection.

  REFERENCES

  1. Gaensbauer JT, Ni Chroinin M. “What we learn in time of pestilence…”. Arch Dis Child Ed Pract 2009; 94:108-114.

  2. Yuksekol I, Ozkan M, Akgul O, et al. Urinary neopterin measurement as a non-invasive diagnositic method in pulmonary tuberculosis. Int J Tuberc Lung Dis 2003;7:771-776.

  3. Malpani BL, Kadival GV, Samuel AM. Radioimmunoscintigraphic approach for the in vivo detection of tuberculomas-a preliminary study in a rabbit model. Nucl Med Biol 1992;19:45-53.

  4. Hazra DK, Lahiri VL, Saran S et al. In vivo tuberculoma creation and its radioimmunoimaging. Nucl Med Communications 1987;8:139-142.

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  Conflict of Interest:
  None declared.

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