Koch’s Postulates, Carnivorous Cows, and Tuberculosis Today, Article Review Example

The paper to be discussed here presents the postulates of Robert Koch (d. 1910) more in terms of their perceived failures — many healthy people are carriers of disease-causing agents; and many of those disease-agents cannot be grown in pure culture because they require a human host to live at all — while acknowledging the postulates’ early success in the fight against tuberculosis in animals and people (Tabrah). A brief history of tuberculosis in society is given.

Tuberculosis (commonly abbreviated to TB), which Tabrah notes still kills two million people per year, is one of the many historical diseases repurposed as AIDS-defining when found infecting those who have tested positive for HIV-antibodies. The worldwide efforts to fight the spread of AIDS/TB are briefly discussed before Tabrah describes the efforts made to update the postulates to include viral and prion diseases, both of which were discovered after Koch’s death. Tabrah explains how prions — misfolded proteins — are especially difficult to explain in conventionally infectious terms because misfolding may not be encoded in their DNA, and even if it is, it is not known how a prion would make a normal protein spontaneously misfold itself too. Prions’ association with Creutzfeldt-Jakob disease and bovine spongiform encephalopathy is noted, as well as the effort to generate a prion with bacterially expressed recombinant prion protein. Tabrah ends his paper with a call for Koch’s Postulates in sociobiology “to explain and possibly avert large self-destructive behaviors” which he feels can be worse than disease.

Tabrah’s paper is valid and useful to a point and has three strengths: 1) it is clearly written and he summarizes the accepted criticisms about the original postulates — we students can safely repeat them and not be challenged; 2) he lists for reference both the classic postulates and the updated version in a form that is understandable for non-scientists; and 3) he drops the last names of two clearly brilliant contemporaries of Koch,[1] whom students can read about.

Those strengths are overshadowed by three weaknesses: 1) The article is mistitled: it should end in “. . . AIDS Today” because “AIDS/TB” is a redefinition of AIDS, not of TB —“AIDS/TB” can mean TB with no clinical AIDS symptoms beyond a positive HIV test; 2) the article seems to at least partially beg the question on the subject of prion diseases, assuming to a degree that they are infectious and then citing the difficulty of proving that assumed infectiousness (“Complicating current revisions and additions to Koch’s postulates is the unique concept of prion diseases . . . about 85% of classic CJD[2] cases occur as a sporadic disease with no recognizable pattern of transmission.” ); 3) Tabrah fails to make clear that the original postulates must still be infallible when used to confirm the non-infectiousness of a disease.

Questions to author. 1) Is it important that Koch’s original postulates’ mandate (“must”) while the updated version only recommends (“should”)? 2) Couldn’t most be replaced with all in: “A nucleic acid sequence belonging to a putative pathogen should be present in most cases of an infectious disease”? And 3) Do you agree that either set of postulates always describe a tightly controlled set of laboratory experiments — that anecdotal reports from the field are invalid?

My opinion is that Koch’s original postulates retain their original value as logic in action. A next step may be to discuss the morality of human postulate-testing on prisoners, justified by  sociobiological Koch’s Postulates, to test “infectious” diseases that may really be non-infectious.

References

Tabrah, Frank L. “Koch’s Postulates, Carnivorous Cows, and Tuberculosis Today.” Hawai’i Medical Journal (2011): 144-148. PDF.

[1] Rudolf Virchow (d. 1902) and Friedrich Loeffler (d. 1915).

[2] Creutzfeldt-Jakob disease.