Mycobacterium marinum causes both long-term subclinical infection and acute disease in the leopard frog (Rana pipiens)

Abstract

Mycobacterium marinum grows at an optimal temperature of 33°C, far lower than that for M. tuberculosis. Consequently, M. marinum infection of mammals is restricted largely to the cooler surfaces of the body, such as the extremities, but it causes a systemic infection in a large number of poikilothermic animals. Here, we describe a laboratory animal model for M. marinum disease in the leopard frog (Rana pipiens), a natural host species. M. marinum causes a chronic granulomatous, nonlethal disease in immunocompetent frogs. Immunosuppression of the frogs with hydrocortisone results in an acute, fulminant, lethal disease. This animal model, in which a spectrum of tuberculosis-like disease can be produced, will be useful for the dissection of the genetic basis of mycobacterial pathogenesis.