A 44-year-old Hispanic man presented with several painful, purulent abscesses on his upper and lower extremities of several weeks duration. He’d been on chronic methotrexate and prednisone therapy for psoriasis and psoriatic arthritis. He was admitted to the hospital with a working diagnosis of cellulitis and was placed on I.V. and PO antibiotic therapy. He was afebrile upon admission. Obtaining Test Results I obtained a skin biopsy and tissue culture. The results revealed deep, dermal necrotizing, granulomatous inflammation with central necrosis and acute inflammation. Special stains included AFB and GMS, which showed the presence of abundant atypical mycobacteria. Tissue culture of the skin grew acid-fast bacilli identified as Mycobacterium abscessus. Background on this bacterium Mycobacterium abscessus is one of the rapidly growing mycobacteria (Runyon group IV), which are ubiquitous in the environment and also include Mycobacterium fortuitum and Mycobacterium chelonei. Recent controversy has emerged regarding the nomenclature of these species because M. abscessus was once thought to be a subspecies of M. chelonei. However, in 1992, quantitative DNA hybridization studies found that M. chelonei and M. abscessus exhibited only 35% DNA homology. Therefore, M. abscessus is now considered a separate species. M. abscessus is reported to cause chronic pulmonary disease and nosocomial infection in hemodialysis and cardiac surgical patients. It has also been known to cause post-injection abscesses and infection in immunocompromised patients. Incubation periods of up to 12 months have been reported. Clinically, skin infection with M. abscessus is characterized by painful exudative nodules. Histopathology reveals a “dimorphic” inflammatory response with polymorphonuclear abscesses and granuloma formation. Tissue culture is the optimal method for diagnosis. Species identification is important because the three rapidly growing mycobacterial species have different antibiotic sensitivities. Identification is achieved by high-performance liquid chromatography. M. abscessus is sensitive to amikacin and cefotoxin. Clarithromycin has also been shown to be effective. More recently, linezolid (oxazolidilone) taken as Zyvox 600 mg PO b.i.d. has been used to successfully treat cutaneous M. abscessus infection. Unfortunately, the high cost of this medication ($45 per tablet), may limit its regular use. Treating the Patient Therapy included I.V. ampicillin/sulbactam sodium, I.V. amikacin and PO clarithromycin. This regimen was successful in reducing the size of the nodules and resulted in overall clinical improvement in the patient’s condition. The patient was discharged on PO clarithromycin. Cutaneous infection with M. abscessus is uncommon, and the diagnosis may be difficult to make. You’ll see this condition more often in immunocompromised patients or those on hemodialysis. Look for signature characteristics, such as painful, exudative nodules. It’s also important to properly identify the bacterium because this dictates therapy. Combination therapy is advised to avoid resistance.
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Cutaneous Infection with Mycobacterium abscessus
A 44-year-old Hispanic man presented with several painful, purulent abscesses on his upper and lower extremities of several weeks duration. He’d been on chronic methotrexate and prednisone therapy for psoriasis and psoriatic arthritis. He was admitted to the hospital with a working diagnosis of cellulitis and was placed on I.V. and PO antibiotic therapy. He was afebrile upon admission. Obtaining Test Results I obtained a skin biopsy and tissue culture. The results revealed deep, dermal necrotizing, granulomatous inflammation with central necrosis and acute inflammation. Special stains included AFB and GMS, which showed the presence of abundant atypical mycobacteria. Tissue culture of the skin grew acid-fast bacilli identified as Mycobacterium abscessus. Background on this bacterium Mycobacterium abscessus is one of the rapidly growing mycobacteria (Runyon group IV), which are ubiquitous in the environment and also include Mycobacterium fortuitum and Mycobacterium chelonei. Recent controversy has emerged regarding the nomenclature of these species because M. abscessus was once thought to be a subspecies of M. chelonei. However, in 1992, quantitative DNA hybridization studies found that M. chelonei and M. abscessus exhibited only 35% DNA homology. Therefore, M. abscessus is now considered a separate species. M. abscessus is reported to cause chronic pulmonary disease and nosocomial infection in hemodialysis and cardiac surgical patients. It has also been known to cause post-injection abscesses and infection in immunocompromised patients. Incubation periods of up to 12 months have been reported. Clinically, skin infection with M. abscessus is characterized by painful exudative nodules. Histopathology reveals a “dimorphic” inflammatory response with polymorphonuclear abscesses and granuloma formation. Tissue culture is the optimal method for diagnosis. Species identification is important because the three rapidly growing mycobacterial species have different antibiotic sensitivities. Identification is achieved by high-performance liquid chromatography. M. abscessus is sensitive to amikacin and cefotoxin. Clarithromycin has also been shown to be effective. More recently, linezolid (oxazolidilone) taken as Zyvox 600 mg PO b.i.d. has been used to successfully treat cutaneous M. abscessus infection. Unfortunately, the high cost of this medication ($45 per tablet), may limit its regular use. Treating the Patient Therapy included I.V. ampicillin/sulbactam sodium, I.V. amikacin and PO clarithromycin. This regimen was successful in reducing the size of the nodules and resulted in overall clinical improvement in the patient’s condition. The patient was discharged on PO clarithromycin. Cutaneous infection with M. abscessus is uncommon, and the diagnosis may be difficult to make. You’ll see this condition more often in immunocompromised patients or those on hemodialysis. Look for signature characteristics, such as painful, exudative nodules. It’s also important to properly identify the bacterium because this dictates therapy. Combination therapy is advised to avoid resistance.
A 44-year-old Hispanic man presented with several painful, purulent abscesses on his upper and lower extremities of several weeks duration. He’d been on chronic methotrexate and prednisone therapy for psoriasis and psoriatic arthritis. He was admitted to the hospital with a working diagnosis of cellulitis and was placed on I.V. and PO antibiotic therapy. He was afebrile upon admission. Obtaining Test Results I obtained a skin biopsy and tissue culture. The results revealed deep, dermal necrotizing, granulomatous inflammation with central necrosis and acute inflammation. Special stains included AFB and GMS, which showed the presence of abundant atypical mycobacteria. Tissue culture of the skin grew acid-fast bacilli identified as Mycobacterium abscessus. Background on this bacterium Mycobacterium abscessus is one of the rapidly growing mycobacteria (Runyon group IV), which are ubiquitous in the environment and also include Mycobacterium fortuitum and Mycobacterium chelonei. Recent controversy has emerged regarding the nomenclature of these species because M. abscessus was once thought to be a subspecies of M. chelonei. However, in 1992, quantitative DNA hybridization studies found that M. chelonei and M. abscessus exhibited only 35% DNA homology. Therefore, M. abscessus is now considered a separate species. M. abscessus is reported to cause chronic pulmonary disease and nosocomial infection in hemodialysis and cardiac surgical patients. It has also been known to cause post-injection abscesses and infection in immunocompromised patients. Incubation periods of up to 12 months have been reported. Clinically, skin infection with M. abscessus is characterized by painful exudative nodules. Histopathology reveals a “dimorphic” inflammatory response with polymorphonuclear abscesses and granuloma formation. Tissue culture is the optimal method for diagnosis. Species identification is important because the three rapidly growing mycobacterial species have different antibiotic sensitivities. Identification is achieved by high-performance liquid chromatography. M. abscessus is sensitive to amikacin and cefotoxin. Clarithromycin has also been shown to be effective. More recently, linezolid (oxazolidilone) taken as Zyvox 600 mg PO b.i.d. has been used to successfully treat cutaneous M. abscessus infection. Unfortunately, the high cost of this medication ($45 per tablet), may limit its regular use. Treating the Patient Therapy included I.V. ampicillin/sulbactam sodium, I.V. amikacin and PO clarithromycin. This regimen was successful in reducing the size of the nodules and resulted in overall clinical improvement in the patient’s condition. The patient was discharged on PO clarithromycin. Cutaneous infection with M. abscessus is uncommon, and the diagnosis may be difficult to make. You’ll see this condition more often in immunocompromised patients or those on hemodialysis. Look for signature characteristics, such as painful, exudative nodules. It’s also important to properly identify the bacterium because this dictates therapy. Combination therapy is advised to avoid resistance.
