Microbes MICROBIOLOGY Mycobacterium marinum, a non-tuberculous pathochromogen with an intermediate growth rate between rapidly and slowly growing mycobacteria, belongs to group I of the Runyon classification ( 57a). M. marinum grows optimally at 28° to 32° C (within 2-3 weeks), while fails to grow on primary isolation at 37°C, a feature that distinguishes this species from M. kansasii. If M. mariunm infection is suspected, the laboratory staff should be notified so that cultures are incubated at optimal temperatures in order to isolate M. marinum. M. marinum lacks catalase and nitrate reductase activities; some isolates, but not all, hydrolyze Tween 80. EPIDEMIOLOGY M. marinum causes disease in many poikilothermic fresh or salt waterfish species over a wide geographic distribution ( 54). While endemic in fish, M. marinum infection in humans, due to contact with contaminated water or fish, is comparatively rare ( 4, 5, 5a, 12, 12a, 40). M. marinum, which was first isolated in 1926 by Aronson from dead saltwater fish in the Philadelphia aquarium ( 6), was recognized as a human pathogen in 1951 by Norden and Linell, who isolated it from skin lesions in swimmers who had bathed in a contaminated pool in Sweden ( 51). The infection was therefore labeled as "swimming pool granuloma" ( 3, 14, 23, 29, 34). Finally, in 1962 Swift and Cohen first reported 2 cases of M. marinum infection from a tropical fish tank; the term "fish tank granuloma" was then devised ( 64). Since those reports, "swimming pool granuloma" has essentially disappeared because of proper chlorination of this reservoir. Various other aquatic environments may imply potential risk, including household aquaria, skin diving ( 68), dolphin training ( 32), and a number of fishing and bathing activities ( 73). In a retrospective survey carried out in 21 Spanish laboratories from 1991 to 1998, 39 bacteriologically confirmed cases were noted ( 17). Culture confirmed M. marinum infection was reported in 66 patients from 1996 to 1998 in France, with an infection incidence of about 0.04 cases per 100.000 inhabitants per year ( 7a). The annual incidence in the USA is 0.27 confirmed cases per 100.000 inhabitants ( 43). The two major risk factors for M. marinum infection in immunocompetent patients are exposure to M. marinum-infested waters and the presence of superficial cuts or abrasions. Almost half (49%) of M. marinum infections are aquarium related, 27% are related to fish or shellfish injuries and 9% are related to injuries associated with salt water or brackish water ( 3). Risk factors for HIV-infected individuals would be similar exposures. Although there has been no reported change in M. marinum infection prevalence and frequency in the developed world since the AIDS epidemic, several cases of disseminated infection in AIDS patients have been described ( 46, 65). It would probably be prudent for HIV infected persons to avoid maintaining freshwater aquaria. CLINICAL MANIFESTATIONS Suspicion of the diagnosis is based on occupational and recreational exposure history. The average incubation period for M. marinum infection is 21 days, although it may be as long as 270 days and 35% of cases have an incubation period of 30 days ( 3). Since lesions may appear somewhat remotely after the time of exposure, eliciting an appropriate history of swimming pool or seawall abrasion, barnacle scrapes, fish fin punctures or possession of tropical fish tanks is critical in making a timely and accurate diagnosis. Given the optimal growth temperature of M. marinum, the infection is primarily localized to the coolest region of the body, which is the skin. Less commonly, it involves deeper structures such as the joints, tendons and bones ( 9, 55, 57, 58, 62). Dissemination of the infection more commonly occurs in immunocompromised hosts, like transplant recipients and subjects on corticosteroid therapy ( 30, 38, 63, 65), while being rarely reported in close-to-intact immunity individuals ( 45, 67). Skin lesions usually appear as papules or nodules on one of the upper limbs, especially on the elbows, fingers and dorsum of hands, progressing to shallow ulceration and scar formation. Most lesions are solitary, although occasional "ascendic" lesions develop that resemble sporotrichosis. Clinical involvement of regional lymph nodes is uncommon. Some of the authors directly observed 15 cases of aquarium-borne infection; among these 12 (80%) were male and 3 (20%) female; male to female ratio was 4:1 ( 12a). Age ranged from 15 to 55 years (mean: 39.9). The infection was occupational in 11 subjects (3 of them worked at an institute aquarium, 8 were in the aquarium selling business) and extra-occupational in 4 patients (all of them tended home aquariums). One of these latter patients was in the 8th month of pregnancy at the time of observation. Every patient had a documented history of former minor trauma, such as abrasion or superficial wound, acquired by handling fish, shellfish or alternativel caused by infected foreign bodies within the aquarium, like wood splinters or stones. The median incubation time after the traumatic inoculation was relatively long, ranging from 3 to 24 weeks (mean: 6.6). Three patients (20%) presented with a single papulo-verrucous plaque and 12 (80%) had a sporotrichoid distribution of nodular lesions. The anatomical distribution of lesions typically affected the upper limbs, at first involving hand fingers and dorsum (right hand in 13 cases, left hand in 2 cases), in 12 cases later spreading centripetally to the whole arm, trailing up the lymphatic vessels. In 3 of these 12 sporotrichoid cases, the first observed lesions were ulcerated nodules causing mild pain, as opposed to the remaining cases, which were painless. Associated systemic symptoms, localized adenopathy, deep structures involvement (tenosynovitis, osteomyelitis, bursitis, Mycobacterium marinum Authors: Domenico Bonamonte MD PhD, Michelangelo Vestita MD Authors (First Edition, 1991 and Second Edition 2002): David E. Griffith, M.D., Richard J. Wallace, Jr., M.D. Table of Contents Microbiology Epidemiology Clinical Manifestations Laboratory Diagnosis Pathogenesis Susceptibility In Vitro and In Vivo Antimicrobial Therapy Endpoint for Monitoring Therapy Prevention Reference Home Editorial Board Reviews Contact Us Search Monograph Tables What's New Reviews History Mycobacterium marinum - Infectious Disease and Antimicrobial Agents http://www.antimicrobe.org/ms05.asp 1 of 8 20-09-2017, 8:04 PM