Mycobacterium Borstelense Isolated from Aquarium Fishes with Tuberculous Lesions

Abstract

Four strains of acid-fast bacilli were isolated from histologically diagnosed tuberculous lesions in 4 aquarium fishes of 3 different sources where the disease had been enzootic and the mortality high. Colonies grew on Loewenstein-Jensen medium within 48 hours of incubation at 28°C. In 32 biochemical tests, pathogenicity tests in mice, and tests for resistance to ethambutol the 4 strains showed an identical behaviour. Some important biochemical characteristics were degradation of PAS and salicylate, arylsulphatase activity, utilization of citrate as carbon source, inability to ferment fructose and to hydrolyse Tween 80, absence of nitratase, and tolerance neither to 5% NaCl nor 0.2% picric acid in growth medium. The strains were avirulent to mice and showed high resistance to ethambutol. When compared with results of corresponding tests on type strains of Mycobacterium borstelense as published from other laboratories a conclusive conformity was revealed. M. borstelense has not previously been associated with fish mycobacteriosis.