A case of INH-resistant tuberculosis after INH monotherapy for latent tuberculosis infection

症例は44歳男性.職業は検査技師病理担当.病理解剖で結核患者から曝露を受け,3ヵ月後にインターフェロンγ遊離試験(Interferon-Gamma Release Assay:IGRA)陽性,胸部単純X線写真とCTで異常は認められなかったため,潜在性結核感染症として暴露の4ヵ月後から6ヵ月間isoniazid(INH)を内服していた.曝露から10ヵ月後くも膜下出血で入院するも,その際の胸部単純X線写真に異常は認められなかった.曝露から2年半後の定期検診時に胸部異常影を指摘され,喀痰塗抹で抗酸菌陽性,結核PCR陽性と判明し加療目的にて紹介となった.入院後INH,rifampicin(RFP),ethambutol(EB),pyrazinamide(PZA)の4剤で加療開始し,特に副作用なく経過し1ヵ月後には菌陰性化,培養陰性化した.臨床経過から4剤での治療は著効していたが,2ヵ月後に薬剤感受性検査でINH,streptomycin(SM)耐性と判明したため,退院後RFP,EBの2剤で9ヵ月加療し治療終了した.治療終了後,2年間の過観察を終えて再発は認めていない.

We report a rare case of INH-resistant tuberculosis developing two years after INH monotherapy for latent tuberculosis infection(LTBI).The patient was in the mid-forties, working as a medical technologist specializing in pathology. He was exposed to Mycobacterium tuberculosis when he conducted autopsy of a tuberculosis patient. Three months later he became positive for interferon-gamma release assay and received INH monotherapy for six months to treat LTBI. During the course of treatment no tuberculous lesion was observed by chest CT.Two and half years after the diagnosis of LTBI, abnormal shadows were noted on chest radiograph in regular check-up. Sputum smears were positive for Mycobacterium, and PCR for tuberculosis was positive. He was hospitalized to Yamaguchi-Ube Medical Center to start chemotherapy with INH, PZA, RFP and EB. Although there was no side effect, his Mycobacterium tuberculosis was found to be resistant to INH, SM, and PAS by drug sensitivity test. After leaving hospital, he was treated with RFP and EB for 9 months until completion of treatment. Since then, no recurrence was noted. Thus, when considering treatment for LTBI, it is important to check the regimen for the person who have caused LTBI and the drug sensitivity of the source of LTBI.

潜在性結核感染症

INH単剤治療

多剤耐性結核