Mycobacterium fortuitum is a Non-Tuberculous Mycobacteria (NTM) commonly found in natural settings like water and soil. Unlike Mycobacterium tuberculosis, which causes tuberculosis, M. fortuitum is generally harmless to most individuals. However, it can lead to infections under specific circumstances, particularly when it enters the body through breaks in the skin or during medical procedures.
Understanding Mycobacterium Fortuitum
Mycobacterium fortuitum is classified as a “rapidly growing” NTM, forming colonies within seven to ten days on culture media. This distinguishes it from slow-growing mycobacteria, which take over two weeks to cultivate. It is frequently found globally in soil, dust, rivers, lakes, and tap water.
Humans primarily encounter M. fortuitum via contaminated water. Exposure can occur during medical procedures, wound care, or recreational activities like pedicures. Direct skin trauma or surgical procedures can also introduce the organism, leading to localized infections. Inhalation of aerosolized contaminated water is another potential route, though less common. M. fortuitum infections are not typically spread from person to person.
While anyone can be exposed to M. fortuitum, certain individuals face a higher risk of infection. Those with compromised immune systems, such as HIV/AIDS patients or those on corticosteroid treatment, are more susceptible. Individuals with pre-existing lung conditions like cystic fibrosis, COPD, or bronchiectasis are at increased risk for pulmonary infections. Patients undergoing surgical procedures or with implanted medical devices are also vulnerable, as the bacteria can establish infections at these sites.
Infections and Clinical Manifestations
Mycobacterium fortuitum causes a range of infections, most frequently affecting skin and soft tissue. These infections often arise following trauma, surgical procedures, or injections, including cosmetic procedures, where contaminated water or instruments may be involved. Symptoms typically include persistent lesions, abscesses, redness, swelling, and drainage, which often do not respond to standard antibiotic treatments. Patients might develop non-healing skin ulcers or subcutaneous nodules.
Pulmonary (lung) infections are less common but can occur, especially in individuals with underlying lung diseases. Symptoms may include a chronic cough, shortness of breath, fatigue, weight loss, and sputum production. Fever and night sweats are less common than in tuberculosis.
In rare instances, particularly in severely immunocompromised individuals, M. fortuitum can lead to disseminated infections. The bacteria spread throughout the body, potentially affecting multiple organs, presenting a more serious clinical picture.
Beyond skin and lung manifestations, M. fortuitum can also cause infections in other body parts. These less frequent infections often result from direct inoculation, affecting areas like bones, joints, or eyes. Examples include osteomyelitis (bone infection) and keratitis (eye infection), often linked to a specific entry point.
Diagnosis and Treatment Approaches
Diagnosing Mycobacterium fortuitum infections can be challenging due to non-specific symptoms that mimic other bacterial or fungal infections. Clinicians consider M. fortuitum when standard cultures yield no growth or infections do not respond to typical antibiotics. Specialized laboratory tests are necessary for accurate identification.
Diagnostic methods begin with collecting appropriate samples, such as tissue biopsies, fluid aspirates, or sputum, depending on the infection site. These samples require specialized mycobacterial cultures, which can take several days to a week for colonies to form, even for this rapid grower. Molecular tests, such as Polymerase Chain Reaction (PCR), offer faster identification and help differentiate M. fortuitum from other mycobacteria. Once identified, antimicrobial susceptibility testing (AST) is important because the organism is inherently resistant to many common antibiotics.
Treatment for M. fortuitum infections typically involves a multi-drug regimen due to its resistance profile. Patients often receive a combination of antibiotics, chosen based on AST results, for an extended period (several months to over a year). For skin infections, treatment may last at least four to six months. Initial treatment for more severe cases might involve intravenous antibiotics, followed by oral agents.
Surgical intervention often aids successful treatment, particularly for localized skin and soft tissue infections or abscesses. Surgical debridement, which involves removing infected tissue, is frequently necessary for a cure. For cases involving foreign bodies like implants or catheters, their removal is often necessary for infection eradication. Long-term follow-up is important to ensure the infection has been fully cleared and to monitor for any recurrence.