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No toxin has ever been identified from R rickettsii. Dr Fumarola's suggestion that endotoxin may play a role in the pathogenesis of Rocky Mountain spotted fever follows the basic pattern of analogy. Even in the best-studied models of endotoxin-associated disease, correlation of toxic activity with pathogenetic mechanisms and disease is far from clear. Dr Fumarola's statement that R rickettsii possesses "some biochemical and biologic activities of endotoxic potency" is not substantiated in the references he cited. The investigations of Schramek et al were performed with members of the typhus group, not R rickettsii. Moreover, although their studies demonstrated a rickettsial lipopolysaccharide in typhus group Rickettsia, the quantity necessary to elicit toxic biologic activities was too large to support the hypothesis of its significance as an important pathogenetic mechanism. Likewise, Dr Fumarola's own article contains no evidence for endotoxin from R rickettsii. In fact, he reviewed studies of many organisms, including
Walker DH, Mattern WD. Renal Failure in Rocky Mountain Spotted Fever-Reply. Arch Intern Med. 1980;140(6):867. doi:10.1001/archinte.1980.00330180141055
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