Mycobacterium marinum Infection After Exposure to Coal Mine Water

ALA-PDT shortens the course of antibiotic therapy for skin infection caused by Mycobacterium marinum

BACKGROUND

Recently, the number of cases of Mycobacterium marinum infection has increased. Due to the nonspecific clinical manifestations and lack of standardized treatment guidelines, these infections are often misdiagnosed and are challenging to treat.

METHODS

In this study, four patients had M. marinum skin infections accompanied by a high-risk exposure history and were diagnosed by bacterial culture and gene chip. Two patients were treated with antibiotic therapy alone, and the other two patients were treated with 5-aminolevulinic acid photodynamic therapy (ALA-PDT) combined with antibiotics.

RESULTS

All four patients enrolled in the study were cured with 100 % efficacy. Two patients were cured after receiving two active antibiotics for 4 months. The other two patients, having considered the drug resistance and intolerance described above, were cured after receiving two active antibiotics for 1-1.5 months along with combination therapy with ALA-PDT.

CONCLUSION

Combination therapy with ALA-PDT and antibiotics was chosen to shorten the duration of antibiotic treatment and reduce the occurrence of adverse reactions.

Mycobacterium marinum: A brief update for clinical purposes

Mycobacterium marinum (M. marinum) is a free-living, slow grower nontuberculous mycobacteria (NTM), strictly related to Mycobacterium tuberculosis, that causes disease in fresh and saltwater fish and it is one of the causes of extra-pulmonary mycobacterial infections, ranging in human from simple cutaneous lesions to disseminated forms in immunocompromised hosts. The first human cases of M. marinum infection were reported from skin lesions of swimmers in a contaminated pool, in 1951, in Sweden by Norden and Linell. Two conditions are required to develop M. marinum infection: (1) skin solution of continuity and (2) exposure to the contaminated water or direct contact with fish or shellfish. The so-called "fish-tank granuloma", the most frequent cutaneous manifestation of M. marinum infection, is characterized by a single papulonodular, verrucose and/or ulcerated granulomatous lesion in the inoculum site. Careful patient's history collection, high clinical suspicion and appropriate sample (e.g. cutaneous biopsy) for microbiological culture are crucial for a timely diagnosis. The treatment is not standardized yet and relies on administration of two active antimycobacterial agents, always guided by antimicrobial susceptibility test on culture, with macrolides and rifampin as pivotal drugs, as well as prompt surgery when feasible. In this narrative review, we provide to Clinicians an updated report of epidemiology, microbiological characteristics, clinical presentation, diagnosis, and management of M. marinum infection.

Mycobacterium marinum

Mycobacterium marinum is a well-known pathogenic mycobacterium for skin and soft tissue infections and is associated with fishes and water. Among nontuberculous mycobacteria (NTM), it is the leading cause of extrarespiratory human infections worldwide. In addition, there is a specific scientific interest in M. marinum because of its genetic relatedness to Mycobacterium tuberculosis and because experimental infection of M. marinum in fishes mimics tuberculosis pathogenesis. Microbiological characteristics include the fact that it grows in 7 to 14 days with photochromogenic colonies and is difficult to differentiate from Mycobacterium ulcerans and other mycolactone-producing NTM on a molecular basis. The diagnosis is highly suspected by the mode of infection, which is related to the hobby of fishkeeping, professional handling of marine shells, or swimming in nonchlorinated pools. Clinics distinguished skin and soft tissue lesions (typically sporotrichoid or subacute hand nodules) and lesions disseminated to joint and bone, often related with the local use of corticosteroids. In clinical microbiology, microscopy and culture are often negative because growth requires low temperature (30°C) and several weeks to succeed in primary cultivation. The treatment is not standardized, and no randomized control trials have been done. Therapy is a combination of surgery and antimicrobial agents such as cyclines and rifampin, with successful outcome in most of the skin diseases but less frequently in deep tissue infections. Prevention can be useful with hand protection recommendations for professionals and all persons manipulating fishes or fish tank water and use of alcohol disinfection after contact.