title: Pulmonary nocardiosis caused by Nocardia cyriacigeorgica in patients with Mycobacterium avium complex lung disease: two case reports.
abstract: BACKGROUND
  Pulmonary nocardiosis frequently occurs in immunocompromised hosts and in some immunocompetent hosts with chronic lung disease; however, few reports have described pulmonary nocardiosis with nontuberculous mycobacterial lung infection. Here we report for the first time two cases of pulmonary nocardiosis caused by Nocardia cyriacigeorgica associated with Mycobacterium avium complex (MAC) lung disease caused by M. avium.
  
  
  METHODS
  Case 1 is that of a 72-year-old Japanese man with untreated MAC lung disease, who was diagnosed with rheumatoid arthritis and initiated on methotrexate. After 3 years of methotrexate therapy, the patient remained smear-negative and culture-positive for MAC, but also became smear-positive for Nocardia species. He received trimethoprim/sulfamethoxazole, and his symptoms and lung infiltrates improved. Case 2 is that of an immunocompetent 53-year-old Japanese woman with MAC lung disease, who was treated with a combined therapy of clarithromycin, rifampicin, ethambutol, and levofloxacin. MAC sputum culture was negative after 1 year of combined treatment, which was maintained for 2 years. After four treatment-free years, Nocardia species were occasionally isolated from her sputum, although MAC was rarely isolated from sputum cultures over the same period. In both cases, the Nocardia species were identified as the recently defined N. cyriacigeorgica by 16S ribosomal RNA gene sequencing.
  
  
  CONCLUSIONS
  We report two cases of pulmonary nocardiosis caused by N. cyriacigeorgica associated with MAC lung disease caused by M. avium and suggest that N. cyriacigeorgica may be a major infective agent associated with MAC lung disease.
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. kazumayagi1214@gmail.com.
authors.forename: Kazuma
authors.initials: K
authors.lastname: Yagi
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. ishii@z6.keio.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ishii
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. hounamugun@gmail.com.
authors.forename: Ho
authors.initials: H
authors.lastname: Namkoong
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. asamitakahiro@gmail.com.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Asami
authors.affiliation: Center for Infectious Diseases and Infection Control, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. lecafe1979@yahoo.co.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujiwara
authors.affiliation: Keio University Health Center, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. km84id@bma.biglobe.ne.jp.
authors.forename: Tomoyasu
authors.initials: T
authors.lastname: Nishimura
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. fumitake@cpnet.med.keio.ac.jp.
authors.forename: Fumitake
authors.initials: F
authors.lastname: Saito
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. kimizucca@gmail.com.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Kimizuka
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. takanori.asakura@gmail.com.
authors.forename: Takanori
authors.initials: T
authors.lastname: Asakura
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. shojis221@gmail.com.
authors.forename: Shoji
authors.initials: S
authors.lastname: Suzuki
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. tetsukamo59@yahoo.co.jp.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Kamo
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. tasaka@cpnet.med.keio.ac.jp.
authors.forename: Sadatomo
authors.initials: S
authors.lastname: Tasaka
authors.affiliation: Division of Clinical Research, Medical Mycology Research Center, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba, Japan. gonoi@faculty.chiba-u.jp.
authors.forename: Tohru
authors.initials: T
authors.lastname: Gonoi
authors.affiliation: Division of Clinical Research, Medical Mycology Research Center, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba, Japan. k.kamei@faculty.chiba-u.jp.|Division of Control and Treatment of Infectious Diseases, Chiba University Hospital, Inohana 1-8-1, Chuo-ku, Chiba, Japan. k.kamei@faculty.chiba-u.jp.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kamei
authors.affiliation: Department of Medicine, Division of Pulmonary Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. tbetsuyaku@z5.keio.jp.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Betsuyaku
authors.affiliation: Center for Infectious Diseases and Infection Control, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. n-hasegawa@z8.keio.jp.
authors.forename: Naoki
authors.initials: N
authors.lastname: Hasegawa
mesh_terms: D000368:Aged; D002908:Chronic Disease; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015270:Mycobacterium avium-intracellulare Infection / Q000150:complications*; D009617:Nocardia Infections / Q000175:diagnosis* / Q000209:etiology