Treatment of Biopsy and Culture Negative Mycobacterium Marinum: Diagnostic and Therapeutic Considerations

February 2014 | Volume 13 | Issue 2 | Case Reports | 204 | Copyright © February 2014

Patrick Tenbrick,a Michael Beer,b and Kenneth Beer MD PAa

aKenneth Beer MD PA Surgical, Cosmetic and General Dermatology, West Palm Beach, FL
bUniversity of Toledo Medical School, Toledo, OH

Mycobacterium marinum () infections are frequently linked to aquatic environments. Cutaneous infections with these organisms cause superficial nodules, ulcerations, and pustules on the skin. Involvement of the deeper tissue may occur when diagnosis and treatment are delayed, allowing the organisms to spread. The diagnostic criteria for infections rely on a detailed patient history, a typical clinical presentation, positive cultures, characteristic organism smear, and if available CR-RFLP analysis and sequencing of 65 kD hsp gene. However, when the pathology is not diagnostic for and the cultures and smears are negative, treatment may be delayed despite clinical suspicion. The accuracy of bacterial cultures and smears for infections has been shown to be variable with ranges between 10% - 60%, leaving many infections unconfirmed.16,17,18 Despite the difficulty in diagnosis, early suspicion of is critical because of the dangers imposed by delayed treatment. Prior reports have documented invasive surgical debridement and amputation due to delayed diagnosis and treatment.20 This case study demonstrates the need for clinical suspicion and accurate patient history for the correct treatment of. The patient reported presented with classic signs and symptoms as well as a strong history of frequent contact with aquariums and with fish obtained during frequent fishing trips but did not have positive stains or a positive culture for The approach to patients such as this one is critical to avoidance of complications and prolonged infections, which can have dire consequences.

J Drugs Dermatol. 2014;13(2):204-206.


Atypical Mycobacterium, also known as nontuberculous mycobacterium, are small, rod-shaped bacilli that cause infections via environmental interactions, with the most common type being Mycobacterium marinum (M marinum).1,2 M. marinum is a saltwater and freshwater environmental bacterium that is a photochromogen classified in Runyon group 1.3,4 M. marinum infections are seen after abrasions or following the introduction of open wounds into wet environments containing the bacteria. These environments are most commonly aquariums, salt-water environments, or direct marine animal contact.1,5
The typical clinical presentation of M. marinum includes superficial nodules, ulcerations, and pustules on the skin. Lesions are usually localized to the extremities, originating around the site of injury and spreading in a linear, sporotrichoid pattern following superficial lymph flow.6,7,8 M. marinum can also cause more severe complications such as tenosynovitis, bursitis, septic arthritis, and osteomyelitis if left untreated.9,10,6,8 The longer the infection is undiagnosed or untreated, the higher the risk of significant morbidities (8). The diagnosis of M. marinum is based on a detailed patient history, physical examination and histological patterns along with positive staining for organisms. Cultures, and CR-RFLP analysis and sequencing of 65 kD heat shock protein are also important for the diagnosis of infection.11,6,12,13 While culture and histological identification are considered critical in the diagnosis of M. marinum, not all cases will be positive. Delayed or inaccurate diagnoses can lead to inappropriate and costly treatments that can potentially harm and extend the M. marinum infection14 as well as protracted infections from lack of treatment. Infections in humans are not common, an estimated 0.27 cases per 100,000 adult patients.10 However, they are important to recognize and to treat in order to prevent long-term infections with the morbidity associated with this. The case presented here is representative of patients that do not have classic histology, staining or positive cultures. The question of how to manage such a patient in the absence of PCR availability is one that is relevant for clinicians presented with this situation.


A 68-year-old man presented to the dermatology clinic complaining of nodules on his hands. He stated that the nodules had first appeared on the dorsum of his dominant (right) hand approximately two months prior to his visit. Since that time, they had spread proximally and he noted swelling of his olecranon bursa. He stated that the lesions were not painful and he denied fever or chills. His social history revealed that he had significant exposure to marine life both as an avid fisherman as well as a salt-water fish hobbyist with tanks that were thousands of gallons. Upon further questioning, he recalled a particular incident when he was stabbed by the dorsal fin of a fish and he believed that the nodules appeared a few weeks after this.
Examination revealed scattered 1- 2cm rock hard nodules on the dorsum of his hand as well as on the dorsal arm (Figure 1). There was diffuse edema and swelling surrounding his elbow. No lymphadenopathy was appreciated in either his axilla or