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• M. tuberculosis in donor corneal tissue
  Soumyava Basu
  Published on: 20 September 2010

• Published on: 20 September 2010

  M. tuberculosis in donor corneal tissue

  • Soumyava Basu, Consultant

  Dear editor, I read with interest Catederal et alâ₉„¢s study on the use of polymerase chain reaction (PCR) for detection of Mycobacterium tuberculosis in donor corneal tissues.1 The authors report the presence of M. tuberculosis DNA in donor corneas of patients with no documented history of tuberculosis. However there are several methodological erro...

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  Dear editor, I read with interest Catederal et alâ€â„¢s study on the use of polymerase chain reaction (PCR) for detection of Mycobacterium tuberculosis in donor corneal tissues.1 The authors report the presence of M. tuberculosis DNA in donor corneas of patients with no documented history of tuberculosis. However there are several methodological errors in the study which need to be discussed. The most significant flaw is the lack of biological plausibility for the presence of M. tuberculosis in the corneal tissue, which is not known to contain any phagocytic cells, except probably at the limbus. The authors have not mentioned the size of the donor corneal button or the degree of corneal vascularization at the limbus. A large corneal button or presence of significant corneal vascularization could account for the detection of mycobacterial DNA in corneal tissue. Besides, the possibility of â€ËÅ“contaminationâ€â„¢ of the corneal surface by the aqueous cannot be ruled out. Even then, the high incidence of M. tuberculosis DNA in â€ËÅ“TB-negativeâ€â„¢ eyes remains unexplained. The authors make a passing reference to the use of positive and negative controls during each amplification reaction, but the nature of these controls or the outcomes after amplification are not mentioned. Did the authors get accurate results with each of the controls? The basis for selection of non-TB donors is also vague as the authors have pointed out themselves. Finally, the authors refer to the low incidence of ocular tuberculosis (1-2%) in patients with pulmonary tuberculosis. However, it is well known that ocular tuberculosis is very rarely seen in patients with systemic tuberculosis.2 Hence the overall incidence of ocular tuberculosis â€â₁“ isolated, as well as in association with systemic tuberculosis, needs to be mentioned. To summarize, the issues highlighted by this study need to reviewed in light of the methodological errors and lack of biological plausibility. Soumyava Basu References: 1. Catedral EJ, Santos RE, Padilla MD, Fajardo-Ang C. Detection of Mycobacterium tuberculosis in corneas from donors with active tuberculosis disease through polymerase chain reaction and culture. Br J Ophthalmol. 2010;94:894-7 2. Donahue HC. Ophthalmologic experience in a tuberculosis sanatorium. Am J Ophthalmol. 1967;64:742-8

  Conflict of Interest:

  None declared

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  Conflict of Interest:
  None declared.

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