Mycobacterium marinum and Mycobacterium fortuitum infections in Siamese fighting fish, Betta splendens (Regan), in Thailand

Abstract

Mycobacterium marinum and Mycobacterium fortuitum are important causative agents of mycobacteriosis in fish
worldwide. Moreover, M. marinum can cause granulomatous skin lesions in humans. The objectives of this study were
to determine the prevalence of Mycobacterium infections in Siamese fighting fish, Betta splendens (Regan), in Thailand
and to evaluate the pathogenicity of the Mycobacterium isolates in goldfish. In the prevalence study, 190 Siamese
fighting fish (15 moribund and 175 clinically healthy fish), collected from culture farms and ornamental fish markets in
Thailand, were included and examined. Mycobacterium spp. were isolated from the kidneys, spleen, liver and gills.
The isolates were then identified on the basis of morphological, biochemical characteristics and the analysis of a partial
16S rRNA gene sequence. The prevalence of Mycobacterium infections in this study was 15/15 (100%) in the moribund
fish and 50/175 (25.71%) in the clinically healthy fish. In the pathogenicity study, 150 clinically healthy goldfish were
used to test for the 2 isolates (Mycobacterium marinum KKVB0901 and Mycobacterium fortuitum KKVB0926). Results
from the test showed that both isolates were pathogenic to experimental goldfish.