Background
Mycobacterium fortuitum is a nontuberculous mycobacterium (NTM), a grouping that encompasses all mycobacteria outside of the Mycobacterium tuberculosis complex. M fortuitum is classified in the Runyon group IV, rapidly growing mycobacteria. It has been found in natural and processed water sources, as well as in sewage and dirt. Distribution is probably worldwide.
Pathophysiology
M fortuitum infection can cause various clinical syndromes. It is an uncommon cause of NTM lung disease. Local cutaneous disease, osteomyelitis, joint infections, and ocular disease (eg, keratitis, corneal ulcers) may occur after trauma. M fortuitum infection is a rare cause of isolated lymphadenitis. Disseminated disease, usually with disseminated skin lesions and soft tissue lesions, occurs almost exclusively in the setting of severe immunosuppression, especially AIDS. Endocarditis has been documented.
Surgical-site infections due to M fortuitum infection are well-documented, especially in association with cardiothoracic surgery. The source is frequently contamination of the wound, directly or indirectly, with colonized tap water. Other nosocomial infections with this organism include infections of implanted devices (eg, catheters) and injection-site abscesses. Pseudo-outbreaks have been associated with contaminated endoscopes. Recent outbreaks have also been described in immunocompetent hosts after use of contaminated whirlpool footbaths in nail salons.[1]
Epidemiology
Frequency
United States
NTM infections are not required to be reported; therefore, exact estimates of disease prevalence and incidence are impossible to determine. The most recent estimates come from voluntary reports tracked by the Centers for Disease Control and Prevention (CDC). From 1993-1996, 4.65-5.99 cases per million persons were reported to the CDC.[2] Sputum was the most frequently reported site, but this may represent a bias in the sites most likely to be cultured for mycobacteria.
Most cases are reported from the southeast United States, including Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, and West Virginia, and the south-central United States, including Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas. Because all cases were likely not reported and some positive culture results may not represent disease, which is perhaps especially true of positive sputum culture results, these numbers may significantly overestimate or underestimate true disease incidence. However, they suggest the general order of magnitude of the situation. An increased appreciation of these organisms as true pathogens may be the reason NTM infection rates are perceived to be increasing, even excluding Mycobacterium avium complex (MAC) infections in persons with AIDS.
International
The World Health Organization does not track NTM infections. Incidence and prevalence undoubtedly vary greatly by locale.
Mortality/Morbidity
- Mortality due to localized M fortuitum infection is rare. Death may result from extensive pulmonary or disseminated disease in patients who are immunocompromised.
- Morbidity depends largely on the site of the infection. Localized skin lesions may eventually heal without therapy or surgical intervention. At other sites, chronic infection is the rule.
Race
No clear racial predilection exists.
Sex
No sexual predominance is known; however, from 1993-1996, more cases reported to the CDC were involved men than did women.[2] Whether this represents a true sex-based preference or reflects a bias in testing and reporting is unclear.
Age
In general, no known age predominance exists. Lung disease in a younger patient (< 50 y) strongly suggests a primary underlying lung disorder. Isolated lymphadenitis primarily occurs in children.
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