"You never asked doc., I do fish"

Mycobacterium marinum: A Case-Based Narrative Review of Diagnosis and Management

Skin and soft tissue infections caused by non-tuberculous mycobacteria are occurring more frequently in recent years. However, chronic skin and soft tissue lesions present a challenge for clinicians, as the diagnostic work-up and definitive diagnosis require knowledge and available laboratory resources. We present here the case of a 66-year-old male patient who presented with painful abscess-like nodules on his right hand and forearm, which worsened after treatment with an anti-TNF-a agent. The fluid specimen taken from the lesion was positive for mycobacteria according to the acid-fast stain. Mycobacterium marinum was identified, first by next-generation sequencing and finally grown on culture, after eight weeks. Acknowledging the complexity of diagnosing and managing infections by non-tuberculous mycobacteria, and especially Mycobacterium marinum, we provide a review of the current epidemiology, clinical characteristics, diagnosis and management of Mycobacterium marinum infection.

Vibrio vulnificus outbreaks in Dutch eel farms since 1996: strain diversity and impact

Vibrio vulnificus is a potentially zoonotic bacterial pathogen of fish, which can infect humans (causing necrotic fasciitis). We analysed 24 V. vulnificus isolates (from 23 severe eel disease outbreaks in 8 Dutch eel farms during 1996 to 2009, and 1 clinical strain from an eel farmer) for genetic correlation and zoonotic potential. Strains were typed using biotyping and molecular typing by high-throughput multilocus sequence typing (hiMLST) and REP-PCR (Diversilab®). We identified 19 strains of biotype 1 and 5 of biotype 2 (4 from eels, 1 from the eel farmer), that were subdivided into 8 MLST types (ST) according to the international standard method. This is the first report of V. vulnificus biotype 1 outbreaks in Dutch eel farms. Seven of the 8 STs, of unknown zoonotic potential, were newly identified and were deposited in the MLST database. The REP-PCR and the MLST were highly concordant, indicating that the REP-PCR is a useful alternative for MLST. The strains isolated from the farmer and his eels were ST 112, a known potential zoonotic strain. Antimicrobial resistance to cefoxitin was found in most of the V. vulnificus strains, and an increasing resistance to quinolones, trimethoprim + sulphonamide and tetracycline was found over time in strain ST 140. Virulence testing of isolates from diseased eels is recommended, and medical practitioners should be informed about the potential risk of zoonotic infections by V. vulnificus from eels for the prevention of infection especially among high-risk individuals. Additional use of molecular typing methods such as hiMLST and Diversilab® is recommended for epidemiological purposes during V. vulnificus outbreaks.

Rare diagnosis of nodular lymphangitis caused by Mycobacterium marinum: MDCT imaging findings

Mycobacterium marinum is an atypical mycobacterium that usually causes a solitary nodule on the hand (“fish tank granuloma”) or less commonly, secondary erythematous channels and nodules spread along lymphatic drainage of the extremity, mimicking sporothricoid skin lesions of nodular lymphangitis. This report presents a case of this rare entity, a nodular lymphangitis caused by Mycobacterium marinum. Multidetector computed tomography (MDCT) imaging was very useful in determining the morphology (cellulitis with a few small subcutaneous nodules and channels) and the extension of the lesion.

Mycobacterium ulcerans causes minimal pathogenesis and colonization in medaka (Oryzias latipes): an experimental fish model of disease transmission

Mycobacterium ulcerans causes Buruli ulcer in humans, a progressive ulcerative epidermal lesion due to the mycolactone toxin produced by the bacterium. Molecular analysis of M. ulcerans reveals it is closely related to Mycobacterium marinum, a pathogen of both fish and man. Molecular evidence from diagnostic PCR assays for the insertion sequence IS2404 suggests an association of M. ulcerans with fish. However, fish infections by M. ulcerans have not been well documented and IS2404 has been found in other mycobacteria. We have thus, employed two experimental approaches to test for M. ulcerans in fish. We show here for the first time that M. ulcerans with or without the toxin does not mount acute or chronic infections in Japanese Medaka "Oryzias latipes" even at high doses. Moreover, M. ulcerans-infected medaka do not exhibit any visible signs of infection nor disease and the bacteria do not appear to replicate over time. In contrast, similar high doses of the wild-type M. marinum or a mycolactone-producing M. marinum "DL" strain are able to mount an acute disease with mortality in medaka. Although these results would suggest that M. ulcerans does not mount infections in fish we have evidence that CLC macrophages from goldfish are susceptible to mycolactones.

Refractory Hand Ulceration: A Case of Chronic Ulceration and Sporotrichoid Spread in a Fish Tank Hobbyist following Mycobacterium marinum Infection

We report the case of a 35-year-old man with a chronic ulceration of the hand in whom an infection with Mycobacterium marinum was diagnosed. Clarithromycin and doxycycline were prescribed, resulting in a slow resolution of the ulceration. M. marinum is a nontuberculous mycobacterium that causes skin lesions such as nodules, ulcerations, and sporotrichoid spread, but may also be responsible for osteoarticular lesions. In this case report, we discuss the clinical characteristics of this condition, as well as its diagnostic methods and treatments.