Infections with organisms of limited habitat, and for which man is not a natural host, usually take place only under well-defined conditions of exposure. These features are well illustrated by Mycobacterium marinum. In cases published to date, M marinum infections have been acquired either from swimming pools or from fish tanks. The following patient summary calls attention again to a hazard of the fish tank and the value of pertinent history in diagnosing a relatively unfamiliar infection.
A 32-year-old man was admitted to Hahnemann Hospital, Philadelphia, on April 25, 1970, because of nodules on the arm. Approximately five weeks previously, he abraded the fifth finger of his right hand while tying string. He washed the abrasion and applied an antiseptic. Two days later, however, the finger became swollen, and shortly thereafter he noted the first of several red nodules along the volar aspect of the forearm. Associated with