Cutaneous infection with Mycobacterium fortuitum: an unusual presentation

Cutaneous Mycobacterium fortuitum Infection: Successfully Treated with Amikacin and Ofloxacin Combination

Cutaneous infections caused by atypical mycobacteria are uncommon and the diagnosis can be missed unless there is strong clinical suspicion supported by laboratory confirmation. We report a case of chronic discharging sinus caused by Mycobacterium fortuitum in a young healthy immunocompetent individual. The patient recovered completely following amikacin and ofloxacin therapy.

Clinical and laboratory aspects of the diagnosis and management of cutaneous and subcutaneous infections caused by rapidly growing mycobacteria

Rapidly growing mycobacteria (RGM) are known to cause pulmonary, extra-pulmonary, systemic/disseminated, and cutaneous and subcutaneous infections. The erroneous detection of RGM that is based solely on microscopy, solid and liquid cultures, Bactec systems, and species-specific polymerase chain reaction (PCR) may produce misleading results. Thus, inappropriate therapeutic measures may be used in dermatologic settings, leading to increased numbers of skin deformity cases or recurrent infections. Molecular tools such as the sequence analyses of 16S rRNA, rpoB and hsp65 or PCR restriction enzyme analyses, and the alternate gene sequencing of the superoxide dismutase (SOD) gene, dnaJ, the 16S-23S rRNA internal transcribed spacers (ITS), secA, recA1, dnaK, and the 32-kDa protein gene have shown promising results in the detection of RGM species. PCR restriction enzyme analyses (PRA) work better than conventional methods at identifying species that are closely related. Recently introduced molecular tools such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), pyrosequencing, DNA chip technology, and Beacon probes-combined PCR probes have shown comparable results in the detection of various species of RGM. Closely related RGM species (e.g., Mycobacterium fortuitum, M. chelonae, and M. abscessus) must be clearly differentiated using accurate molecular techniques because their therapeutic responses are species-specific. Hence, this paper reviews the following aspects of RGM: (i) its sources, predisposing factors, clinical manifestations, and concomitant fungal infections; (ii) the risks of misdiagnoses in the management of RGM infections in dermatological settings; (iii) the diagnoses and outcomes of treatment responses in common and uncommon infections in immunocompromised and immunocompetent patients; (iv) conventional versus current molecular methods for the detection of RGM; (v) the basic principles of a promising MALDI-TOF MS, sampling protocol for cutaneous or subcutaneous lesions and its potential for the precise differentiation of M. fortuitum, M. chelonae, and M. abscessus; and (vi) improvements in RGM infection management as described in the recent 2011 Clinical and Laboratory Standards Institute (CLSI) guidelines, including interpretation criteria of molecular methods and antimicrobial drug panels and their break points [minimum inhibitory concentrations (MICs)], which have been highlighted for the initiation of antimicrobial therapy.

Multifocal keloids associated with Mycobacterium fortuitum following intralesional steroid therapy

We report a case of subcutaneous abscess formation with Mycobacterium fortuitum following intralesional steroid injection into multifocal keloids. A high index of suspicion of atypical mycobacteria infection is needed in patients with a history of skin and soft tissue infections, in particular late-onset infections, which are negative for routine bacterial cultures and without a clinical response to antibiotics used for acute pyogenic infections.

Mycobacterium abscessus bacteremia in an immunocompetent patient following a coronary artery bypass graft

Sternal osteomyelitis with bacteremia due to Mycobacterium abscessus is rarely seen in immunocompetent hosts. Routine pyogenic cultures in these cases are often negative causing a delay in diagnosis and treatment. Clinicians and microbiologists should rule out the possibility of infection due to nontuberculous mycobacteria while managing cases of nonhealing culture-negative wounds with conventional antibiotic therapy. We report a case of bacteremia secondary to a nonhealing sternal wound due to M. abscessus. A combination of radical debridement and prolonged antimicrobial therapy helped in the complete eradication of the infection.

Pleural effusion in an immunocompetent woman caused by Mycobacterium fortuitum

Mycobacterium fortuitum is a non-tuberculous mycobacterium that can cause pneumonia, abscess and empyema in subjects with predisposing lung diseases. However, pleurisy with effusion is rare. Herein, we report the case of a 74-year-old immunocompetent female patient without apparent risk factors, who suffered haemorrhagic pleural effusion as the main clinical manifestation. Pleural nodules were detected by computed tomography scan, and microbiological analysis revealed M. fortuitum in the absence of other pathogens. The patient was treated with ceftriaxone and ciprofloxacin, and full recovery ensued in 4 weeks. To our knowledge, this is the first reported case of haemorrhagic pleural effusion in an immunocompetent patient without underlying diseases. Although non-tuberculous mycobacterial infections are rarely accompanied by pleural involvement, M. fortuitum should be considered in such cases, especially when microbiology fails to detect the usual pathogens, and when the clinical picture is unclear.