PerspectiveInfectious Disease

Adapting Koch's postulates

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Science  15 Jan 2016:
Vol. 351, Issue 6270, pp. 224-226
DOI: 10.1126/science.aad6753

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  • RE: Adapting Koch's postulates

    IN THEIR PERSPECTIVE “Adapting Koch’s postulates” (15 January 2016, P.224), Byrd and Segre proposed an updated 4-step protocol that incorporates sequencing and culturing to take microbial interactions into account in proving disease causation. Building upon Koch’s original disease concept (1 pathogen = 1 disease), they proposed two new models: 1 pathogen + 1 colonization resistor = 0 disease, and 1 pathogen + 1 resistor community = 0 disease. All these proposals are well overdue and they are fundamental to human, veterinary and plant medicines. Here we propose an additional model: 1 pathogen + 1 promoter or promoter community = 1 disease. Many pathogens are now known to produce and use chemical signals to coordinate their actions to their advantage in disease cycle; some of these signals are shared among species of different taxonomic levels from species to kingdom (1). Presence of one or more of these signal-sharing species, which are here termed promotor species or community, increases the likelihood of initiating a successful infection by another species. This has been observed in a number of bacterial diseases and similar evidence is emerging for diseases caused by other groups of pathogens. Among the most significant are Phytophthora species, a group of eukaryotic oomycetes. Phytophthora nicotianae and P. sojae are destructive pathogens on their respective host plants (2), while P. hydropathica is a new species only known to attack a few shrubs (3). Infection by P. ni...

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    Competing Interests: None declared.
  • RE: Adapting Koch's postulates

    Koch's postulates made a huge contribution to the understanding of infectious diseases at the end of the 19th century and for many decades to follow. Nowadays, they should not be adapted but rather gold framed and kept as a scientific relic in the infectious diseases hall of fame. They should instead be replaced by a new set of criteria dictated by the meteoric advances in microbiome science.
    The quintessence of Koch's postulates is the presence or absence of a definite microbe at a specific point in time. Currently, we know that this requirement is only one of multiple components of an equation which may be extremely complicated for many diseases.
    For example, one third of the human population including more than two billion people are infected by Mycobacterium tuberculosis and the vast majority of these individuals have latent asymptomatic disease. Only less than one in ten of these persons will develop symptomatic tuberculosis. As stated in the old literature, some persons with latent tuberculosis may actually have some degree of protection against reinfection or reactivation of Mycobacterium tuberculosis infection similarly to persons who have been vaccinated with BCG (an attenuated live tuberculous bacillus which remains latent in vaccinated persons).
    The majority of infections seen in modern medicine are caused by endogenous micro-organisms which have been accepted members of the microbiota and caused an infection only after relocation to...

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    Competing Interests: None declared.