Medication Summary
The mainstay of therapy for infection by M marinum is antimicrobials, including antibiotics and antimycobacterials.
The organism is generally sensitive to rifampin plus ethambutol, tetracyclines (minocycline [MCN], [40] doxycycline [DCN]), trimethoprim-sulfamethoxazole (TMP-SMZ), clarithromycin, [41] and fluoroquinolones (ciprofloxacin, ofloxacin, sparfloxacin). Resistance to doxycycline and rifampin has been reported but is rare. [42, 43]
Antimicrobials are administered singly or in combination. [37] Single-agent therapy may be sufficient in uncomplicated infection of the skin; however, combination therapy is used when more extensive infection is treated. Combination antimycobacterial agents include the following:
-
Rifampin and ethambutol: This combination is regarded as highly effective therapy, especially for severe disease or in patients with impaired immune systems.
-
Streptomycin, ethambutol, and isoniazid
-
Clarithromycin, alone or in combination: This agent has shown the most efficacy of the macrolide antibiotics. One case report discusses the use of azithromycin in combination with ethambutol. Erythromycin has not demonstrated efficacy for treating M marinum infections.
Combining rifabutin or rifampin with macrolide antibiotics is not recommended because of the decreased efficacy of the macrolide and the increased levels of rifabutin or rifampin.
Most strains of M marinum have been found to be resistant to medications typically used for Mycobacterium tuberculosis, including isoniazid, streptomycin, pyrazinamide, and para-aminosalicylic acid. [34] In contrast, ethambutol is effective in combination with antimycobacterial or antibiotics, but not as a single agent.
The duration of therapy is empiric; multiple sources recommend extended therapy for 4-6 weeks following clinical resolution of lesions. [37]
Antimicrobial agents
Class Summary
Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting. Therapy must be taken regularly and continued for a sufficient period.
Rifampin (Rifadin, Rimactane)
Rifampin has been found to be effective as monotherapy and is successful when given in combination with another antimicrobial. It inhibits DNA-dependent bacterial RNA but not mammalian RNA polymerase. Cross-resistance may occur.
Ethambutol (Myambutol)
Ethambutol is only effective when combined with another antimicrobial agent, preferably rifampin. It diffuses into actively growing mycobacterial cells (eg, tubercle bacilli). It impairs cell metabolism by inhibiting the synthesis of one or more metabolites, which, in turn, causes cell death. No cross-resistance has been demonstrated. Mycobacterial resistance is common with previous therapy.
Minocycline (Dynacin, Minocin) or Doxycycline (Doryx, Vibramycin)
Minocycline is effective monotherapy; however, strains of M marinum resistant to doxycycline but sensitive to minocycline have been reported. It also treats infections caused by susceptible gram-negative and gram-positive organisms, in addition to infections caused by susceptible Chlamydia, Rickettsia, and Mycoplasma species.
Trimethoprim and sulfamethoxazole (Bactrim, Septra)
Several case reports have shown the effectiveness of this drug combination. Reports indicate that it can help eradicate organisms unresponsive to either antituberculars or tetracyclines. It inhibits bacterial growth by inhibiting the synthesis of dihydrofolic acid.
Clarithromycin (Biaxin)
Cases of organisms resistant to conventional antitubercular therapy have responded to clarithromycin but not erythromycin. Use of azithromycin has not been reported. Clarithromycin inhibits bacterial growth, possibly by blocking the dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest. It has bactericidal activity against atypical Mycobacterium species (eg, M marinum).
Ciprofloxacin (Cipro)
Fluoroquinolones are effective alone or in combination with other medications to eradicate M marinum. Ciprofloxacin inhibits bacterial DNA synthesis and, consequently, growth.
Levofloxacin (Levaquin)
Levofloxacin is used for the treatment of tuberculosis and some atypical mycobacterial infections in combination with rifampin and other antituberculosis agents.
-
Photograph of Mycobacterium marinum infection lesions.
