A culture from a tropical fish store manager’s wound grew on Lowenstein-Jensen agar at 30C but not at 37C. What is the most likely identification?

The identification of the organism grown on Lowenstein-Jensen agar at 30°C but not at 37°C is indicative of Mycobacterium marinum. This species is known to be associated with aquatic environments, particularly tropical waters and fish. It typically causes skin and soft tissue infections in humans, especially those who handle fish or work in aquaculture settings.

Mycobacterium marinum has a unique growth temperature preference, thriving at lower temperatures around 30°C, which aligns with the culture results, while it is unable to grow optimally at the higher temperature of 37°C that is more characteristic of human pathogens.

In contrast, other Mycobacterium species listed in the question have different growth characteristics and pathogenic profiles. Mycobacterium tuberculosis, for instance, is a human pathogen that flourishes at 37°C, which rules it out in this scenario. Mycobacterium kansasii and the Mycobacterium avium-intracellulare complex have different growth conditions as well and are typically associated with pulmonary infections rather than cutaneous ones and have different temperature tolerances that would not fit the scenario presented.

Thus, the growth characteristics at specific temperatures and the association with tropical fish handling lead to the