A 29-year-old female from South China with a history of swelling, discharge, and chronic abscesses of the right breast for more than 10 days presented to the Department of Breast Surgery in the Second Affiliated Hospital, Sun Yat-sen University, Guangzhou, China. About one month prior, the patient had noted a painful mass in the right breast and a mini-invasive operation was performed. The patient did not have a history of fever, night sweats, weight loss, and respiratory symptoms. In addition, there was no family history of breast cancer and no personal history of tuberculosis. The patient was referred to an outpatient surgery clinic, where a breast ultrasound demonstrated a duct ectasia hypoechoic lobulated mass measuring 16.7 mm x 9.8 mm in the lower quadrant of the right breast and palpable lymph nodes in the ipsilateral axilla. Blood tests showed that full blood count, renal function, liver function, thyroid function, and blood glucose were all within normal limits. The patient was treated with a variety of antibiotics, including doxycycline, clindamycin, and amoxicillin-clavulanic acid for 10 days, without success. The patient underwent drainage of the right breast and 1 ml of purulent fluid was aspirated.
Specimens were sent for routine bacteriology, acid-fast bacteria stain, Gram stain, fungal stains, and culture. Acid-fast bacilli were not found, and Gram staining of the pus showed that numerous polymorphonuclear leukocytes were present, however, without any organisms. The pus was plated on Columbia agar containing 5% sheep blood and incubated at 37 C in air supplemented with 5% CO2. Three days after incubation, the presence of strain GHY 970 was confirmed. The colonies that were present on the blood agar plates were identified with 16S rDNA PCR and phylogenetic analysis. Genomic DNA was extracted with the TIANamp Genomic DNA Kit (cat. No. #DP304-02), according to the manufacturer's guidelines. Bacterial 16S rDNAs were amplified by PCR using the combination of a universal primer 1492r (5' GGT TAC CTT GTT ACG ACT T 3') and bacterial primer 27f (5' AGA GTT TGA TCC TGG CTC AG 3'). PCR was performed using a thermal cycler with the following cycling parameters: 95 C for 5 min as initial denaturation followed by 30 cycles of 94 C for 30 s, 55 C for 30 s, 72 C for 1 min, and 72 C for 7 min as final extension. After purification, the amplified products were sent to BGI Company for sequencing analysis. Homology search was performed using BLAST (https://www.ncbi.nlm.nih.gov) and the differences in nucleotide sequences between various bacteria were determined using the sequence alignment editor "BioEdit". Products were further analyzed by MEGA 6.0. The Neighbor-Joining (NJ) tree was constructed using the Kimura-two-parameter (K2P) distance model. Phylogenetic analysis of the 16S rDNA gene sequence of strain GHY 970 revealed the species of M. abscessus (Figure 1). NCBI data search indicated >99% sequence identity to the M. abscessus DS27 (KU362955). Because the patient's treatment with antibiotics was discontinued, a new breast nodule appeared in the right breast, and the patient was treated with a combination of rifampicin, isoniazid, and pyrazinamide. After 3 months of treatment, the mass in the right breast and axillary lymph nodes had totally disappeared. The entire treatment therapy was completed by 6 months and, at follow-up after 1 year, there were no signs of recurrence or any other issues.