Mycobacterium marinum is a slow growing, photochromogenic
mycobacterium species belonging to Group 1 of the Runyon's classification.
Direct microscopic examination of the specimen showed acid-fast bacilli with subsequent formation of typical colonies of a relatively rapidly growing photochromogenic Mycobacterium spp.
The isolates we observed by acid-fast staining of the specimens and recovered on LJ medium were a yellow pigmented photochromogenic species that grew rapidly at 25[degrees]C, 37[degrees]C, and 42[degrees]C.
Although presumptive identification can rely on a few biochemical and phenotypic tests such as production of photochromogenic
pigment, negative nitrate reduction, and positive tests for urease and Tween 80 hydrolysis, definitive identification involves reverse hybridization techniques, or, alternatively, high-performance liquid chromatography analysis of mycolic acids and DNA sequencing assays (22,23).
A heavy growth of photochromogenic
mycobacteria was detected in 3 sputum cultures.
The slow-growing, photochromogenic
mycobacterium has been isolated from both surface and tap water and has been associated with a nosocomial pseudo-outbreak suspected to have originated from a contaminated hospital water supply (2).
Abbreviations: d = days; N = nonpigmented; P = photochromogenic
; R = rough; S = smooth; + = at ]east 85% strains positive; -- = at least 85% negative; V = variable.