Mycobacterium branderi isolated from pus of a right pulmonary cavitary lesion.

*Corresponding author: Mailing address: Mycobacterial Reference Center, The Research Institute of Tuberculosis, 3-1-24 Matsuyama, Kiyose, Tokyo 204-0022, Japan. Tel: +81-424-935075, Fax: +81-424-92-4600, E-mail: sugawara@jata.or. jp A 22-year-old male truck driver who presented for a regular physical checkup was found to have an abnormal shadow in the right lung and was therefore referred to Tokushima Red Cross Hospital in September, 2004. Chest CT revealed a cavitary lesion in the right upper lung field. He was hospitalized at Higashi-Tokushima National Hospital for probable pulmonary tuberculosis, and at that time there were no symptoms. Chest CT showed an encapsulated cavitary lesion about 3 cm in diameter in the right S2 area adjacent to the pleura, and no dispersing abnormal shadows. Results of various tests included: tuberculin test 11×11 mm, sputum negative for Mycobacterium tuberculosis, PCR negative for M. tuberculosis, ESR 3 mm/h, CRP 0.0 mg/dl, serum Aspergillus antigen >5 positive, Cryptococcus neoformans antigen negative, β-D-glucan <5 negative. Partial thoracoscopic resection of the right lower lobe was performed. The pus from the cavitary lesion showed Gaffky 5, acid-fast bacteria that could not be identified by PCR and DNA-DNA hybridization (Kyokuto Pharmaceutical Industry Co., Tokyo, Japan). The Research Institute of Tuberculosis (RIT) was therefore asked to identify the bacteria. Histopathological examination of the surgical specimen showed caseating pulmonary granulomas with Ziehl-Neelsen-stained bacteria. No fungi were evident. As shown in Table 1, we carried out routine biochemical tests on the clinical isolate in comparison with standard strains of Mycobacterium branderi (ATCC51789) and Mycobacterium celatum (ATCC51131). The growth characteristics and biochemical test results for this M. branderi were similar to those of standard strains. Only tellurite reduction showed a difference between M. branderi and M. celatum. Although it has been reported that the M. celatum type I standard strain is positive for tellurite reduction whereas clinical isolates are negative, our isolate was positive for tellurite reduction whereas the M. celatum standard strains in our laboratory were negative (1). We carried out an rpo B assay (2), but this was unable to distinguish M. branderi from M. celatum. We then performed 16S rRNA sequencing of this isolate, the M. branderi standard strain, and M. celatum. At present, 16S rRNA gene sequencing remains the sole definitive means of distinguishing between them (3). Results of a similarity search using a partial 16S ribosomal DNA database showed that our isolate had 99.7% identity with M. branderi and 93.3% identity with M. celatum. Our isolate was therefore judged to be M. branderi. We then carried out susceptibility tests (Table 2). Previous studies have provided interpretations of MICs determined for Mycobacterium avium isolates (4-6), and these guidelines were the only basis available for a tentative interpretation of the susceptibility patterns of the M. branderi isolates in this study. The susceptibility patterns observed for the clinical isolate and the M. branderi standard strain included resistance to amikacin and rifampin and susceptibility to clarithromycin, ciprofloxacin, ethambutol, ethionamide and streptomycin (7). These patterns were similar to that of M. celatum. Our isolate is similar to the Helsinki strain and M. branderi in the second of two cases reported by Wolfe et al. (1). Finally, we carried out animal infection experiments using Hartley female guinea pigs. When 1× 10 CFU of the isolate was administered subcutaneously and necropsy was performed 7 weeks later, several small granulomas were observed in the lungs and the liver microscopically (Fig. 1). Such granulomas were not recognized in the spleen or kidneys of the guinea pig. From the medical history of this patient, the cavitary lesion in the right lung appeared to have been induced