某醫學中心Mycobacterium chimaera-intracellulare group假性群聚感染事件調查

Cluster of Mycobacterium Chimaeraintracellulare Group Cases in a Taiwanese Medical Centre

從檢驗室常規監測資料顯示某醫院2020年7月接受支氣管鏡檢查有6位病人的支氣管沖洗液培養出M. chimaera-intracellulare group，為釐清是否為群聚感染，進而著手調查。於支氣管鏡檢查區，內視鏡清洗區、消毒區及儲存區，採檢相關物品、溶液及環境檢體共23件，及經內視鏡自動洗滌機清洗消毒後的支氣管鏡內管及外管檢體共16件；合計採樣39件檢體。以脈衝式膠體電泳（pulsed-field gelelectrophoresis; PFGE）對培養出之M. chimaera-intracellulare group作分子生物分型。6位病人的支氣管沖洗液培養出之M. chimaera-intracellulare group以PFGE進行基因型態分析，結果發現非同一基因型。23件環境檢體檢驗結果，12件未檢出M. chimaera-intracellulare group，8件檢體呈現細菌汙染，3件培養結果為M.abscessus（非本次事件之非結核分枝桿菌﹝nontuberculous mycobacterium；NTM）。16件支氣管鏡內管及外管檢體皆未檢出。另由胸腔專科醫師審閱病歷，當下無病人發生相關感染之情形，持續再追蹤6個月，個案亦無發生感染。此事件所幸6位病人之M. chimaera-intracellulare group非同一基因型，故判定為偽群突發事件（pseudo-outbreak）。環境檢體雖未培養出M. chimaeraintracellulare group，但於內視鏡自動洗滌機的內置濾心管壁及外置過濾器之濾心管壁檢出M. abscessus。顯示若未依據儀器使用說明定期更換自動洗滌機內的濾心，及未訂定自動洗滌機之清洗管理原則，則內視鏡自動洗滌機易被NTM汙染。

The Mycobacterium chimaera-intracellulare group was isolated from the bronchoalveolar lavage (BAL) fluids of six patients in July 2020 in a medical centre in Taiwan. This study investigates the presumed outbreak that started on 20 September 2020. Generated genotype patterns of these six M. chimaera-intracellulare group isolates using pulsedfield gel electrophoresis (PFGE) indicated that they were of different strains, suggesting a pseudo-outbreak of infection due to M. chimaera-intracellulare group. Notably, no M. chimaera-intracellulare group was isolated from a total of 39 specimens, including 23 specimens sampled from detergents, flushing fluid, disinfectants, autonomic washing machines, and the general environment, as well as 16 specimens of swabs of the inner and outer surfaces of cleaned and previously disinfected flexible bronchoscopes. Furthemore, no radiographic or clinical evidence of pulmonary infections was found by pulmonologists in patients in whose BAL fluid the M. chimaera-intracellulare group was grown, had neither at the instant assessments nor at follow-up evaluations six months later. However, two M. abscessus isolates each were found to grow on the swab specimens sampled from: (i) the inner side of the water pipe infusing tap water into the autonomic washing machine and (ii) the inner side of water infusion pipe in the washing machine. The ends of these water infusing pipes were connected to a filter for blocking microorganisms. These pseudooutbreak events emphasize the importance of establishing an evidence-based standard operating procedure strictly adhered to by staff engaged in bronchoscopy, as well as close monitoring for the emergence of NTM in BAL fluid.