Phylum Actinobacteria, Class Actinobacteria, Order Actinomycetales, Suborder Corynebacterineae, Family Mycobacteriaceae, Genus
Mycobacterium, Mycobacterium hippocampi Balcazar et al. 2014.
Species description is based on a single isolate.
Acid-alcohol-fast, irregular rods, 0.4 x 1.2-1.4 µm. Non-motile. Non-spore-forming.
Colonies on Lowenstein–Jensen medium supplemented with 1.5 % (w/v) NaCl are
circular and 1.5-2.0 mm in diameter, orange (scotochromogenic). Optimum growth
temperature is 25 ºC. No growth occurs below 15 ºC or above 35 ºC. Grows at pH 5.0-
10.0. Grows in 0-6% (w/v) NaCl media.
Opportunistic pathogen associated with infections in aquatic animals.
Isolated from an aquarium seahorse (Hippocampus guttulatus) with tail rot and from the spleen of European sea bass (Dicentrarchus
Susceptible to ciprofloxacin (5 µg/ml), clarithromycin (15 µg/ml), and rifampin (5 µg/ml). Resistant to isoniazid (10 µg/ml),
thiophene-2-carboxyli hydrazide (2.0 µg/ml), hydroxylamine (500 µg/ml), thiacetazone (10 µg/ml), picrate (1000 µg/ml).
- Balcazar JL, Planas M, Pintado J. Mycobacterium hippocampi sp. nov., a rapidly growing scotochromogenic species isolated from
a seahorse with tail rot. Curr Microbiol 2014; 69:329-333.
- Stathopoulou P, Asimakis E, Petropoulos Y, Tsiamis G. 2020. Draft genome sequence of Mycobacterium hippocampi DL,
isolated from European sea bass (Dicentrarchus labrax). Microbiol Resour Announc 9:e00816-20. https://doi.org/10.1128/MRA.
Description is based mostly on API 20NE and API ZYM (bioMerieux) results.
Positive results for arginine dihydrolase, acid and alkaline phosphatase, catalase, esculin, esterase (C4), esterase lipase (C8),
naphthol-AS-BI-phosphohydrolase, alpha- and beta-glucosidase, lipase, leucine arylamidase, urease, valine arylamidase, cystine
arylamidase, and glucose fermentation.
Can assimilate glucose, mannitol, potassium gluconate and malate.
Negative results for alpha-fucosidase, indole production, gelatin hydrolysis, alpha- and beta-galactosidase, beta-glucuronidase,
N-acetyl-beta-glucosaminidase, alpha-mannosidase, nitrate reduction to nitrite, N-acetyl-D-glucosamine, oxidase, trypsin and
No assimilation of arabinose, mannose, maltose, caprate, adipate, citrate and phenyl-acetate.
(c) Costin Stoica