Koch's Postulates and the Pathogenesis of Comparative Infectious Disease Causation Associated with Bartonella species

Abstract

In his homage to Lucretius ('Georgica'), Vergil is credited with stating: 'Felix qui potuit rerum cognoscere causas' ('Fortunate is he who knows the causes of things'). Based on numerous commentaries and publications it is obvious that clinicians, diagnosticians and biomedical research scientists continue to struggle with disease causation, particularly in the assessment of the pathogenic role of 'stealth pathogens' that produce persistent infections in the host. Bartonella species, because of their evolutionary ability to induce persistent intravascular infections, present substantial challenges for researchers attempting to clarify the ability of these stealth bacteria to cause disease. By studying the comparative biological and pathological behaviour of microbes across mammalian genera, researchers might be able more rapidly to advance medical science and, subsequently, patient care by undertaking focused research efforts involving a single mammalian species or by attempting to recapitulate a complex disease in an rodent model. Therefore, in an effort to further assist in the establishment of disease causation by stealth pathogens, we use recent research observations involving the genus Bartonella to propose an additional postulate of comparative infectious disease causation to Koch's postulates.

Identification of Bartonella henselae in the Liver of a Thoroughbred Foal with Severe Suppurative Cholangiohepatitis

“…also described 2 dogs with granulomatous hepatitis in which B. henselae and B. clarridgeiae DNA was amplified from the liver 11. In dogs and people, B. henselae also has been associated with peliosis hepatis, a vasculoproliferative disorder resulting in formation of multiple blood‐filled cavities in the liver 12, 13…”

Bartonellosis, One Health and all creatures great and small

“…In the context of comparative infectious disease causation, B. henselae was amplified and sequenced from the liver of a dog with peliosis hepatitis, a unique pathological lesion initially reported in B. henselae infected HIV patients and from another dog with granulomatous hepatitis, a histopathological lesion reported with some frequency in B. henselae-infected children and adults. 3,14 Bartonella clarridgeiae DNA was amplified and sequenced from the liver of a Doberman dog with copper storage disease and from the aortic valve of a dog with vegetative valvular endocarditis. 2,3 Bartonella elizabethae, a species that infects rodents, was found in a dog that had shown chronic weight loss culminating in sudden unexplained death and from a human endocarditis patient.…”

“…berkhoffii and B. henselae in dogs. 14,38 In dogs, Bartonella species appear to contribute to the development of dermatological lesions indicative of a cutaneous vasculitis, panniculitis, as well as anterior uveitis, polyarthritis, meningoencephalitis and immune-mediated haemolytic anaemia. 3,13,47 Additional research efforts, using carefully designed case-controlled studies, are necessary to establish the frequency and extent to which Bartonella spp.…”

It shouldn’t happen to a dog … or a veterinarian: clinical paradigms for canine vector-borne diseases

“…immune-mediated haemolytic anaemia), or 'idiopathic', may actually result from persistent infection with one or more so-called 'stealth pathogens'. Indeed, the complexity of proving disease causation by organisms such as Bartonella has recently prompted the proposal that a fifth postulate should be added to Koch's postulates [40].…”