某醫學中心新生兒加護病房仙人掌桿菌菌血症群聚處理與環境調查經驗

Successful Control of a Cluster of Bacillus Cereus Bacteremia in a Neonatal Intensive Care Unit

仙人掌桿菌（Bacillus cereus）是環境中的常在菌，但可在免疫缺損者，造成侵襲性感染。2021年5月，本院新生兒加護病房（NICU），陸續出現仙人掌桿菌菌血症病例，我們啟動一連串感染管制措施，包括5,000 ppm漂白水加強環境清消等作為，但無法完全阻止新病例發生。為了釐清可能的環境污染來源，我們在NICU進行兩次環境採檢，並將採集的菌株進行PFGE基因型比對。我們發現，兩次採檢平均陽性率分別為25.5%（13/51）與32.4%（22/68），第二次採檢五個臨床單位，陽性率介於14.3%至42.9%間，環境物品檢出率，以被單收納櫃與黃疸照光燈最高（80%），體重計與呼吸器螢幕面板次之（60%），病人服收納盒再次之（50%）。菌株PFGE分析發現，26株細菌共可分出13種基因型，以D、W型（各4株）和T型、AB型（各3株），為主要基因型，W與T型是當時臨床菌株的所屬基因型，在環境中主要由被單收納櫃與毛巾收納櫃檢出，顯示布巾類用品受污染，是造成感染的主要來源。在全面更改以滅菌方法處理布巾，並嚴格分開存放已滅菌布包與非滅菌布包後，即控制群聚無新病例產生。結論：仙人掌桿菌十分普遍，無法以目前常用的全面清消方法，完全由醫療環境中將其消除。針對可能污染物品作滅菌清消，特別是與患兒親密接觸的布單類，是防治加護病房中仙人掌桿菌侵襲性感染的有效方法。

Bacillus cereus is a ubiquitous organism commonly found in the environment. Immunocompromised individuals may sometimes become infected with invasive diseases caused by this organism. In May 2021, a cluster of B. cereus bacteremia was identified in the premises of a neonatal intensive care unit (NICU). A series of infection control measures were initiated, including the use of highly-concentrated bleaching solutions to decontaminate the environment, but they were unable to stop new cases. To clarify the possible sources of the organism, we collected and cultivated environmental samples of B. cereus in the NICU. Genotypes of the identified bacteria were analyzed using pulsed-field gel electrophoresis (PFGE). The yield rates of B. cereus in the two runs of environmental sampling were 25.5% and 32.4%, respectively. In the second run of sampling of the five subunits of the NICU, the yield rates ranged from 14.3% to 42.9%. The object with the highest detection rate was light for phototherapy (80%), followed by the weight scales (60%), the screen panel of the ventilators (60%), and storage cabinets for patient clothing (50%). PFGE analysis of 26 environmental strains identified 13 genotypes, with types D and W (shared by four strains each), and types T and AB (shared by three strains each) being the most prevalent types. Types W and T were also the major genotypes identified in the clinical strains. They were mainly detected in the storage cabinets for sheets and towels, suggesting that contaminated linens might be the major source of infection. After changing the method used to sterilize the linens and strictly separating the storage of sterilized and non-sterile linens, the cluster was successfully controlled. B. cereus is common in the healthcare environment and cannot be eliminated using common infection control measures. Sterilization targeting contaminated items, especially the linens that were in close contact with patients, was an effective way to control the cluster of invasive infections of B. cereus in the NICUs.