A 54-year-old Italian, Caucasian woman with a history of autoimmune thyroiditis was seen at the surgical unit for pain, redness and swelling of the left breast which had developed over the preceding 72 hours. The patient had been on 10 mg prednisone for 1 month secondary to autoimmune hemolytic anemia. On physical examination, she was afebrile. Erythema and edema of both areolar and peri-areolar areas of the left breast were present with dimensions of about 9 ×6 cm and with homolateral tender lymph node enlargement. Acute bacterial mastitis was the initial diagnosis and cefotaxime 2 g/day was prescribed for the first 2 weeks. At this point, due to persistence of symptoms, breast ultrasound, mammography, fine needle aspiration, and tru-cut needle biopsies were performed. Histopathology results were consistent with a chronic inflammatory reaction. Subsequently, a draining sinus developed and a pus sample was sterile.
One week later, another swab grew both Pseudomonas luteola
and Staphylococcus epidermidis
prompting us to perform a second needle aspirate. Cefotaxime 1 g TID and oral ciprofloxacin 500 mg BID were prescribed for a total of 3 weeks. During this period, mild improvement was seen but as the fistula closed her symptoms relapsed so it was decided to perform surgical excision of the abscess. At surgery, galactophora ducts were found to be filled with purulent material. Also a mass of 9.5 × 7 × 5 cm, with cavitation and purulent material, was excised. Once again, histopathology reports showed a chronic inflammatory reaction with giant cells. About 1 week after surgery, the inflammation reappeared and a third needle aspirate was performed. This time, M. abscessus
was identified and confirmed in two subsequent cultures [1
]. Acid-fast bacilli (AFB) were also seen in the pus after Zhiel-Neelsen staining (Figure ). At this point, the patient was transferred to the infectious diseases service.
(A) Acid fast bacilli in pus (arrow) on Zhiel-Neelsen staining; (B) Chest CT scan showing a soft tissue abscess 4.5 × 3 cm (arrow) with a cutaneous fistula.
On admission, the patient had an area of inflammation of about 6 × 7 × 4 cm in the external quadrants of her left breast. A few days later, a fistula formed and microbiological tests confirmed the presence of M. abscessus.
The isolated strains were identified by the reverse hybridization method (INNO-LiPA, Belgium) and confirmed by genetic sequencing [1
]. Antimycobacterial susceptibility tests were performed in microdilution broth (MHB, BioMérieux, France) [10
]. M. abscessus
results were as follows: susceptible: clarithromycin (MIC 0.125 mg/L) and amikacin (MIC 2 mg/L); intermediate susceptible: cefoxitin (MIC 16 mg/L) and imipenem (MIC 8 mg/L); resistant: ciprofloxacin (MIC 8 mg/L), doxycycline (MIC 8 mg/L), co-trimoxazole (MIC >64 mg/L) and linezolid (MIC 32 mg/L). Abnormal laboratory test results are listed in Table . HIV serology was negative, CD4+ lymphocytes were normal and blood cultures were negative for AFB. Therapy consisting of clarithromycin 500 mg BID, imipenem 1 g BID and amikacin 1 g/day was started. The latter was discontinued after 2 weeks due to possible vestibular side effects. Prednisone was also discontinued without recurrence of hemolysis. A chest CT scan confirmed left breast soft tissue and glandular involvement (Figure ). Thirty-two days after admission, the inflammation was considerably reduced and the patient was discharged on clarithromycin 500 mg twice a day. Only 1 week later, the patient had to be readmitted because of recurrence. An ultrasound scan showed a hyperechogenic area with hypoechogenicity and aspiration was performed. This time, AFBs were not identified in the pus and the cultures were negative. Imipenem was restarted with clarithromycin for a further 3 weeks. Thereafter, clarithromycin alone was prescribed for another 10 weeks. Eighteen months after treatment discontinuation, the patient remains disease-free.
Clinical, laboratory findings and therapy