Mycobacterium chelonae is a rapidly growing mycobacterium that causes skin and soft tissue infections after trauma in immunocompetent individuals and in immunocompromised hosts with disseminated disease, especially in patients with rheumatic diseases receiving immunosuppressive therapy.1–3

We report the case of a 29-year-old woman whose medical record included systemic lupus erythematosus, sarcoidosis and a 4-year history of sickle cell anemia plus β-thalassemia. At the time of writing, she was being treated with rituximab (she had received 2 cycles of 1g each), azathioprine 100mg/day, methylprednisolone 16mg/day and hydroxyurea 1g/day. She was admitted to a quaternary care center with a 3-month history of pain in her right hip. Drug treatment with a variety of analgesics and multiple local injections in right hip and gluteus resulted in a partial improvement of her symptoms. One month later, the clinical symptoms returned and she presented with an abscess in right gluteus, with local inflammatory changes. Physical examination revealed the presence of a painful nodule. She underwent surgical drainage of the abscess, and cultures for the usual bacteria, fungi and mycobacteria (auramine–rhodamine stain and culture in Löwenstein–Jensen solid medium) were negative. Antibiotic therapy was initiated with ceftriaxone+vancomycin and ampicillin/sulbactam, with no improvement whatsoever. A biopsy was performed with the drained material, and the latter was analyzed by polymerase chain reaction (PCR) for the detection of mycobacteria, in which M. chelonae DNA was isolated. The patient began treatment with clarithromycin 1g/day and moxifloxacin 400mg/day in May 2014, with which she continued at the time of writing, with resolution of the clinical condition.

Nontuberculous mycobacteria constitute a group of species that includes Mycobacterium abscessus (with 3 subspecies), M. chelonae and Mycobacterium fortuitum, which are widely distributed in nature.4

As a pathogen in humans, M. chelonae has a number of clinical forms, the severity of which ranges from frequent mild skin and soft tissue infections to potentially fatal systemic infections.

Skin infection is the most common clinical condition in immunocompetent individuals, and is usually preceded by an injury, open fracture, wound from a sharp, cutting weapon, or a surgical procedure (especially plastic surgery).5

In immunocompromised individuals, this pathogen causes disseminated skin infections, and the entry route or route of transmission is generally unidentified. The clinical manifestations consist of infections in organs and skin abscesses that generally affect the lower extremities. Localized injuries can also cause infections (cellulitis, abscesses and osteomyelitis), as can surgical wounds and catheters, although to a lesser degree.

It is important that general practitioners, when treating patients with autoimmune diseases and using biologic therapies, have a high index of suspicion of infection by M. chelonae, founded on 3 criteria: (a) a previous skin lesion, mainly from cosmetic or surgical procedures; (b) the presence of painful subcutaneous nodules and abscesses at the site of the lesion; and (c) a poor or inadequate response to the antibiotic therapy received.6

The diagnosis starts with the direct observation of mycobacteria in the aspirate of secretions or in the tissue obtained, using Ziehl–Neelsen or auramine–rhodamine stain, plus the performance of special cultures for the diagnosis. The classical Ziehl–Neelsen technique and the fluorescence technique with auramine–rhodamine are equally effective for the diagnosis, but around 30% of the rapidly growing mycobacteria can exhibit negative fluorescence with the auramine-rhodamine technique. Thus, when infection by rapidly growing mycobacteria is suspected, the procedure of choice is the Ziehl–Neelsen stain.

Bacteriological culture enables us to enhance the sensitivity of the diagnosis; even if the result of direct observation is negative, the disease is not ruled out. Therefore, sampling should be carried out for DNA amplification using the PCR technique, to obtain the patterns of sensitivity to first-line and second-line drugs that serve as a guide to the most adequate and effective treatment.7