fortuitum

Fortuitum most commonly refers to Mycobacterium fortuitum, a species of rapidly growing non-tuberculous mycobacteria (RGM). It occurs naturally in soil, dust, and water and is not part of the Mycobacterium tuberculosis complex. It is one of several environmental mycobacteria capable of causing human disease.

Mycobacterium fortuitum grows rapidly on routine mycobacterial media, typically forming colonies within 3–7 days. Colonies are usually non-pigmented and may range from smooth to rough in appearance. The organism is considered non-photochromogenic, producing no pigment in light or dark conditions.

Clinically, it commonly causes skin and soft tissue infections after trauma, surgery, cosmetic procedures, or injections. It can also cause postoperative wound infections, catheter- or prosthesis-related infections, osteomyelitis, keratitis, and, less frequently, pulmonary or disseminated disease in individuals with underlying lung disease or immunocompromise.

Diagnosis relies on microbiological culture and identification. Acid-fast bacilli may be seen on staining, and species-level identification is achieved by molecular methods such as 16S rRNA sequencing, hsp65, or rpoB gene analysis, or by MALDI-TOF mass spectrometry. Antimicrobial susceptibility testing is recommended due to variable resistance patterns.

Treatment typically requires combination therapy guided by susceptibility results and may include a macrolide (for example, clarithromycin or azithromycin) in combination with agents such as amikacin, cefoxitin, imipenem, doxycycline, or fluoroquinolones. Duration is usually several months, and removal of infected devices or surgical drainage may be necessary for optimal outcomes.

Fortuitum is found worldwide in environmental reservoirs, with outbreaks occasionally linked to hospital water systems or cosmetic procedures. Prognosis depends on site and host factors; localized skin infections often respond to therapy, whereas disseminated disease carries higher risk in immunocompromised patients.