Volume 18, Number 1—January 2012
Pulmonary Infection Caused by Mycobacterium conceptionense
To the Editor: Mycobacterium conceptionense was first identified in 2006 from a patient with posttraumatic osteitis (1). Since then, 3 more isolates have been recovered from a subcutaneous abscess (2), a wound after breast surgery (3), and an abscess after a fat injection (4). During November 2009 through April 2010, M. conceptionense was isolated from sputum from 4 patients in 2 tertiary hospitals in South Korea.
Patient 1, a 69-year-old woman, was admitted to Seoul National University Bundang Hospital in 2005 with fever and pleuritic chest pain. She had a long history of recurrent fever and cough. Computed tomography (CT) showed multifocal nodular lung lesions with lymphadenopathy. After 7 days of treatment with cefuroxime and azithromycin, the patient’s fever subsided and radiographic lesions disappeared. She was discharged with negative culture results. After discharge, she had recurrent episodes of fever, and CT showed waxing and waning pulmonary lesions. Nontuberculous mycobacteria (NTM) species were isolated from some sputum cultures: M. smegmatis in 2006; M. avium in 2007; and M. intracellulare in 2008 and 2009. In February and April 2010, her respiratory symptoms and chest CT findings indicated more severe disease, and M. conceptionense grew in sputum cultures. After treatment with clarithromycin, rifampin, and ethambutol for 2 months, the patient’s symptoms improved and sputum culture results were negative.
Patient 2, a 70-year-old man with Parkinson disease, was referred to Seoul National University Bundang Hospital in November 2009 for a small nodular lung lesion detected by CT during a medical checkup. He exhibited no pulmonary symptoms. Routine laboratory test results were within normal limits. M. conceptionense was isolated from sputum. Clarithromycin was prescribed for 10 days, and the patient remains asymptomatic.
Patient 3, a 70-year-old man with tongue cancer, was admitted to Seoul National University Hospital in March 2010 with exacerbated dyspnea. In November 2009, CT had indicated new nodular lung lesions and chemotherapy had been started. Chest CT in 2010 showed increased size and extent of nodular infiltration, which suggested pulmonary infection rather than cancer metastasis. From 2 sputum samples, 2 isolates of M. conceptionense were identified. In addition, Streptococcus pneumoniae grew in blood and sputum cultures. Despite treatment with broad-spectrum antimicrobial drugs, the patient died of respiratory failure.
Patient 4, a 53-year-old man, sought care at Seoul National University Hospital in 2008 for chest discomfort. Other than having diabetes mellitus, he had been healthy. Chest CT showed multiple lung nodules. Sputum culture grew M. tuberculosis. The patient received isoniazid, rifampin, ethambutol, and levofloxacin for 6 months, during which time sputum cultures were negative. In April 2010, follow-up sputum culture grew M. conceptionense. The patient was asymptomatic and followed up without treatment.
Cultures for each patient were conducted at the respective hospitals, where sputum specimens were placed on solid media (Ogawa; Shinyang, Seoul, South Korea) and in liquid media (MGIT 960; Becton Dickinson, Sparks, MD, USA) after decontamination with NaOH. For all 6 specimens, acid-fast bacilli grew 4–7 days after incubation in liquid media.
Molecular identification was conducted at Seoul National University Bundang Hospital, where PCR restriction fragment length polymorphism and multiplex real-time PCR and melting curve analyses were performed as described (5,6). Each method produced identical results for all but did not support specific identification. PCR restriction fragment length polymorphism profiles and melting peaks for the isolates from patients 1–4 were similar to those of M. septicum and M. fortuitum. Sequence analyses of the 652-bp fragment of tuf and the 527-bp and 1,571-bp fragments of 16S rDNA genes were performed (7,8). The tuf sequences of isolates from patients 1, 3, and 4 showed 100% identity with the M. conceptionense type strain, 98.2% homology (11-bp difference) with M. porcinum, and 98.1% homology with M. fortuitum. The tuf sequence of the isolate from patient 2 differed by 2 bp from the others. The 16S rDNA sequence of the isolate from patient 1 showed 100% homology with sequences of M. conceptionense and M. senegalense and 99.9% (2-bp difference) homology with M. farcinogenes. Broth microdilution susceptibility tests for isolates from patients 1, 2, and 4 showed susceptibility to amikacin, ciprofloxacin, clarithromycin, and doxycycline but resistance to cefoxitin, sulfamethoxazole, rifampin (MIC >16 μg/mL) and intermediate-resistance to imipenem (MIC 8–16 μg/mL).
According to the American Thoracic Society diagnostic criteria for NTM lung disease (9), patient 1 fulfilled all criteria and patient 3 fulfilled the radiographic and microbiological criteria. These findings suggest that M. conceptionense can cause lung disease. For the other patients, colonization with M. conceptionense is a more plausible explanation (Table).
These 4 recent cases of M. conceptionense infection are in accordance with the increasing prevalence of NTM (10). Increasing prevalence might be the result of technical advances in NTM identification, including use of liquid media and sequencing, or the result of a local outbreak or contamination event. We consider contamination to be an unlikely cause because specimens were completely separated from each other during collection and testing. Isolates from different patients yielded distinct randomly amplified polymorphic DNA patterns. In conclusion, M. conceptionense is not a rare NTM species in South Korea and can cause pulmonary disease.
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