Mycobacterium marinum Susceptibility (AST)−Broth Dilution

Mycobacterium marinum isolate from a primary clinical specimen should be submitted on conventional solid or broth AFB broth medium.

Pure culture isolate on an AFB conventional solid medium or a minimum of 1 mL of AFB broth medium

Conventional or broth medium, tightly sealed, in etiologic agent packaging

Determine the susceptibility of Mycobacterium marinum isolates to relevant antimycobacterial agents. Routine susceptibility testing of M. marinum isolates is generally not recommended.^1,2 The following agents are typically found to be susceptible when testing M. marinum: Rifampin, Ethambutol, Doxycycline, Minocycline, Clarithromycin and Trimethoprim-sulfamethoxazole.³ Disease due to M. marinum is generally localized and the number of organisms is low, with 95% of tissue biopsies reported as AFB smear negative. Susceptibility testing should be considered when patients remain culture positive after several months of therapy.⁴

Susceptibilities cannot be reported if the organism fails to grow in the test medium. Susceptibilities cannot be performed on mixed cultures.

This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

Sensititre® broth microdilution (MIC)

Few comparative studies have been performed relating clinical outcome with in vitro susceptibility testing. Ciprofloxacin is not recommended for therapy because some strains are resistant and with monotherapy, the risk of mutational resistance increases.