TB growth from formalin

From:Vinnie Della Speranza

Fred and others,
this seems like a good time to share what I have learned regarding the growth of TB from formalin fixed tissue stemming from a question I posted.
There is very little information reported in the literature. It appears that most reports of TB growing from formalin are anecdotal and not the result of scientific study. I'd like to thank Tim Morken for assisting me with a PubMed search and forwarding along the citations he found.
A good reference for anyone so inclined is
Kappel, TJ et al. The Viability of Mycobacterium tuberculosis in Formalin-Fixed Pulmonary Autopsy Tissue: Review of the Literature and Brief Report,  Human Pathology Vol 27 No 12 (Dec 12, 1996) p1361-1364
The authors of this paper attempted to culture TB from five formalin fixed cases with no success.
A later letter to the International Journal of Tubercle Disease 2(6): 521-523, 1998 by Gerston, KF and Gafoor, H. stated that these authors attempted to grow TB from 25 formalin fixed cases. Of these, three cases, fixed for 4.5, 6.5 and 9 weeks respectively, did grow TB in culture.
While this information is of some value, it emphasizes that additional study is needed before we can really understand what this information means to the way we practice. Is it possibe that an aqueous aldehyde fixative has difficulty fully penetrating caseous, necrotic granulomas? Clearly the TB organism has a talent for sequestering itself from the ravages of the immune system and it may well be that it is sufficiently isolated as to limit its exposure to a variety of external forces including tissue fixation.
Vinnie Della Speranza
Manager for Anatomic Pathology Services
Medical University of South Carolina
165 Ashley Avenue  Suite 309
Charleston, SC 29425
Ph: 843-792-6353
fax: 843-792-8974

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