非結核分枝桿菌群聚感染事件：真或偽之探討

Investigation of an NTM Cluster in a Southern Medical Center Psychiatric Hospital

南部某醫學中心精神科院區於2010年5月5日發現第一例痰液耐酸性染色試驗（acid fast stain, AFS）陽性病人時，即依據法規通報肺結核，同時依據接觸者定義進行接觸者調查及相關感染管制措施。自檢出第一例痰液AFS陽性病人起，截至同年8月30日，共調查142位接觸者，其中十七位病人痰液AFS或分枝桿菌培養報告為陽性：其中六位AFS陽性，其培養結果為四位陰性、兩位非結核分枝桿菌（non-tuberculous mycobacteria, NTM），包括一位Mycobacterium abscessus、一位無法鑑定至種名；另外十一位AFS陰性病人，分枝桿菌培養結果皆為NTM，包括一位M.abscessus、四位M.fortuitum、四位M.gordonae及兩位無法鑑定至種名。整個調查期間長達四個月，排除院內有流行病學之關聯性，因此判定為非結核分枝桿菌偽群聚感染事件。由於精神科病人的病史較難確認、並有參與團體治療與共同活動、加上公共活動的空間密閉而有限，因此若有一例AFS陽性病人出現，就會伴隨大量的接觸者（包括其他病人及員工）。醫師為了怕錯失潛藏結核病病人的診治，將會針對無症狀之接觸者進行檢驗，可能因此篩檢出許多沒有症狀卻有陽性檢驗結果的病人，導致了偽群聚感染事件。藉由探討此非結核分枝桿菌事件，改善處理流程與介入措施，謹供同類醫療機構參考。

In May 2010, two cases with sputum positive for acid-fast bacteria were found in the psychiatric district of a medical center in southern Taiwan. After related investigations were performed on these two patients (acid-fast stain [AFS], tuberculosis [TB] culture, and chest x-rays [CXR]), four AFS-positive and 11 TB culture (broth)-positive cases were detected. The infection control group started to intervene in the first case that was confirmed to be AFS-positive. According to specifications in the Diseases Bulletin formulated by the Disease Control Department in the Ministry of Health and Welfare, Executive Yuan, the patient was categorized as an open tuberculosis case. At the same time, the infection control group also processed contact investigations and related infection control measures. Since the first AFS-positive case was detected on May 5, 2010, 17 patients were tested until August 30. Six of them were AFS-positive and were confirmed as open tuberculosis cases immediately (TB culture results of these six cases were: four-no growth, and two-non-tuberculous mycobacteria (NTM), of which one was Mycobacterium abscessus, while the other remained unidentified). The other eleven patients were AFS-negative, and their TB culture results all revealed NTM (one-M. abscessus, four-M. fortuitum, four-M. gordonae, and two remained unidentified). After a 4-month period of investigation and handling, the event was finally identified as not an NTM clustering event. Psychiatric patients may be involved in clustering events because of behavioral characteristics caused by their disease (unclear description of symptoms), treatment (day care and group therapy activities), and daily activities in an enclosed space with limited public interactions. For fear of missing potential cases, physicians checked all patients and found that many asymptomatic patients also had positive test results. Since the report of the first TB culture-positive case, in which a M. tuberculosis infection was indistinguishable from an NTM infection, the decision to treat or isolate patients was made on the basis of the clinical experience of the doctors and infection control staff. Fortunately, this event did not cause any injury to patients or staff. Consequently, we re-examined patient TB screening procedures and physical examination specifications for staff (including outsourced staff members) in order to correct and reinforce TB screening in patients. Furthermore, this allowed us to rethink whether AFS-positive patients in psychiatric departments should have more auxiliary definitions, or whether there is a need to have more examinations to define cases in a timely manner to allow for isolation measures to prevent the spread of the disease. By sharing this experience, we hope to provide a reference for other psychiatric care facilities.