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_Mycobacterium marinum_ is one of the non-tuberculous mycobacterium
or NTM (that is, a grouping outside of the _M. tuberculosis_ complex)
that is found in cold or warm, fresh or salt water. NTM are
characterized by their rate of growth in vitro and pigment production.
Organisms in the _Mycobacterium chelonae-abscessus_ group are
non-pigmented rapidly growing NTM species (RGM) that produce mature
growth on agar plates within 7 days of incubation and include _M.
fortuitum_ and the _M. chelonae-abscessus_ group. Slowly growing NTM
include _M. kansasii_ and _M. avium/intracellulare_ complex and
require more than 7 days to produce mature growth on agar plates. _M.
marinum_ is an intermediately growing NTM and a photochromogen,
meaning pigment is produced when cultured and exposed to light. 7-10
days are required to produce mature growth of _M. marinum_ on agar
plates and growth is optimal at 32 deg C [89.6 deg F].
_M. marinum_ infection occurs following skin and soft-tissue injuries
that are exposed to an aquatic environment or fish. First described as
"swimming-pool granuloma", when swimming pools were not routinely
chlorinated, _M. marinum_ skin infections are now most often acquired
from aquarium maintenance and called "fish tank granuloma". The
infection usually presents as indolent, localized nodular or
ulcerating skin lesions on mainly the upper limb of otherwise healthy
hosts, but can evolve into an ascending lymphangitis that resembles
sporotrichosis or can spread to deeper tissues, resulting in
tenosynovitis, arthritis, and osteomyelitis. Spread to deeper
structures, such as tendon, joint, and bone, was noted in 29 per cent
of the 63 cases of culture-confirmed _M. marinum_ infection in a
national survey conducted in France (1). Delay in diagnosis (2) and
immunologic impairment (2) have been noted to be a frequent component
of invasive _M. marinum_ infections. Bone marrow invasion and
bacteremia are rare and have been seen only in profoundly
immunocompromised patients (2,3).
Rifampin and ethambutol in combination are reported to be the
antibiotics used most often (1,2,4). Other antibiotic options with
reliable activity include clarithromycin, doxycycline, and minocycline
(4). Antimicrobial agents that have been noted to have less reliable
activity include trimethoprim/sulfamethoxazole (5) and the
fluoroquinolones (6). _M. marinum_ is also susceptible to linezolid
(6), but resistant to isoniazid and pyrazinamide (4). The duration of
therapy is at least 3 months (4) and is significantly longer for
patients with deeper structure infections than for patients with
infections limited to the skin and soft tissue -- the median duration,
7-11 months (1,2) vs 4 months (2), respectively. Most cases of
invasive _M. marinum_ infection will also require surgical debridement
as an adjunct to antimicrobial treatment (1,2,4,7).
References
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1. Aubry A, Chosidow O, Caumes E, et al. Sixty-three cases of
_Mycobacterium marinum_ infection: clinical features, treatment, and
antibiotic susceptibility of causative isolates. Arch Intern Med 2002;
162(15): 1746-52. Available at
<http://archinte.ama-assn.org/cgi/content/full/162/15/1746>.
2. Lahey T. Invasive _Mycobacterium marinum_ infections. Emerg Infect
Dis 2003; 9(11): 1496-7. Available at
<http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3035536/>.
3. Parent LJ, Salam MM, Appelbaum PC, Dossett JH. Disseminated
_Mycobacterium marinum_ infection and bacteremia in a child with
severe combined immunodeficiency. Clin Infect Dis 1995; 21(5): 1325-7.
Abstract available at <http://www.ncbi.nlm.nih.gov/pubmed/8589169>.
4. Diagnosis and treatment of disease caused by nontuberculous
mycobacteria. Am J Respir Crit Care Med 1997; 156(2 Pt 2): S1-S25.
Available at
<http://ajrccm.atsjournals.org/cgi/content/full/156/2/S1>.
5. Rhomberg PR, Jones RN. In vitro activity of 11 antimicrobial
agents, including gatifloxacin and GAR936, tested against clinical
isolates of _Mycobacterium marinum_. Diagn Microbiol Infect Dis 2002;
42(2):145-7. Abstract available at
<http://www.ncbi.nlm.nih.gov/pubmed/11858912>.
6. Braback M, Riesbeck K, Forsgren A. Susceptibilities of
_Mycobacterium marinum_ to gatifloxacin, gemifloxacin, levofloxacin,
linezolid, moxifloxacin, telithromycin, and quinupristin-dalfopristin
(Synercid) compared to its susceptibilities to reference macrolides
and quinolones. Antimicrob Agents Chemother 2002; 46(4): 1114-6.
Available at <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC127113/>.
7. Wendt JR, Lamm RC, Altman DI et al. An unusually aggressive
_Mycobacterium marinum_ hand infection. J Hand Surg 1986; 11(5):
753-5. Abstract available at
<http://www.ncbi.nlm.nih.gov/pubmed/3760509>. - Mod.ML]