Delayed diagnosis of M. marinum infections leads to more complicated disease
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The diagnosis of Mycobacterium marinum infection can be delayed by a number of factors, including poor documentation of water exposure, atypical clinical presentation and empiric antibiotic treatment prior to a definitive diagnosis, according to a recent study.
In addition, delayed diagnosis can lead to complicated cases, which can increase symptom duration and lead to more surgical debridements.
“Mycobacterium marinum or ‘fish tank granuloma’ is a pathogenic, nontuberculous mycobacterium that has been associated with skin, soft tissue, joint, bone and disseminated infections,” Natalia E. Castillo, MD, of the Division of Infectious Diseases at the Mayo Clinic College of Medicine and Science, and colleagues wrote. “It is an endemic fish pathogen widely distributed in aquatic environments such as fish tanks, swimming pools and natural bodies of water. Despite [the] increasing number of cases reported in recent years, the diagnosis of M. marinum is often missed or delayed.”
Castillo and colleagues conducted a retrospective study to establish risk factors for this infection, as well as describe treatment and outcomes in patients with complicated and uncomplicated M. marinum. Researchers identified culture-confirmed M. marinum infections from the Mayo Clinic Clinical Mycology Laboratory between January 1998 and December 2018.
The search identified 12 cases of complicated M. marinum infection. The patients with a complicated infection were older (64.3 ± 11.1 vs. 55.8 ± 14.5; P = .03), had longer duration of symptoms (5 vs. 3 months; P = .011) and had more surgical debridements (1 vs. 0; P < .001). These cases also required more medications and longer treatment.
Antibiotic susceptibility tests were performed in 59% of all patients included in the study and showed that all isolates were susceptible to clarithromycin. In addition, of the tetracyclines, doxycycline demonstrated a better susceptibility pattern.
“Diagnosis of M. marinum infection should be suspected based on the history and physical examination and confirmed using histologic evaluation and mycobacterial cultures. Delay in diagnosis may lead to complicated M. marinum infection,” the authors concluded. “Most experts recommend treatment with two active agents for uncomplicated M. marinum cases. However, our study shows no difference in the number of drugs used and clinical outcome. Monotherapy combined with surgical debridement is usually sufficient to cure M. marinum infection.” – by Caitlyn Stulpin
Disclosures: The authors report no relevant financial disclosures.
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