Rapid control of a hospital-wide outbreak caused by extensively drug-resistant OXA-72-producing Acinetobacter baumannii

Extensively drug-resistant Acinetobacter baumannii (XDRAb) emerges as an important pathogen of health care–associated infections and outbreaks worldwide. During January and February 2006, there was a hospital-wide outbreak of XDRAb at a medical center in Taiwan. Without limiting the usage of carbapenems or the closure of any ward, this outbreak was effectively controlled. We investigated the molecular epidemiology and reported the infection control experiences. XDRAb is defined as A baumannii that is resistant to multiple antibiotics but susceptible to tigecycline and polymyxin B. During the outbreak, the clinical and environmental XDRAb isolates were collected and studied by antimicrobial susceptibility testing, pulsed-field gel electrophoresis, and polymerase chain reaction for Verona integron-encoded metallo-beta-lactamases, imipenemases, and oxacillinases (OXA). Our measures to control the outbreak included private room isolation of patients until there were three successive negative cultures, reinforcement of contact precautions, daily environmental cleansing with room-dedicated cleaning tools and sodium hypochlorite, and careful auditing of adherence. During the outbreak, 32 clinical XDRAb isolates came from 13 patients who were hospitalized in four intensive care units and three wards. Most (7 of 13, 53.8%) cases were associated with a surgical intensive care unit. The results from pulsed-field gel electrophoresis study indicated that all isolates were of one genotype. All 32 isolates harbored ISAba1-blaOxA-51-like and blaOxA-72 genes. After this outbreak till August 2010, further incidences of XDRAb were sporadic cases of XDRAb with different clones and did not reach the level of outbreak. To our knowledge, this is the first reported hospital-wide outbreak caused by OXA-72 carbapenemase–producing A baumannii in the Asia-Pacific region, with successful and sustained control. Although the source or vehicle of the outbreak was not identified, our results suggest that a hospital-wide outbreak can be successfully managed with strict infection control measures, and that the limitation of the use of carbapenems and closure of wards may not be necessary.

摘要有效處理廣泛耐藥鮑曼不動桿菌(extensively drug-resistant Acinetobacter baumannii, XDRAb)群突發仍是許多醫院之難題。台灣某醫學中心於2006年一至二月，發生一起XDRAb多病房群突發，在未限制carbapenems使用及不關病房下，落實易執行之感控措施，有效控制該群突發。本研究分析該群突發之分子流行病學並分享成功經驗。XDRAb定義為除了tigecycline及polymyxin B外，對多種抗生素具抗藥性之A baumannii。群突發期間同時收集病患及其病室環境之XDRAb進行抗生素感受性試驗及脈衝場凝膠電泳，並進行VIM、IMP metallo-beta-lactamases及OXA carbapenemase之聚合酶鏈鎖反應與定序。感染控制措施包括：單人病室隔離、隔離至連續三套追蹤培養陰性、加強接觸防護、每日以病室專用器具及次氯酸鈉清潔消毒，並確實監督措施遵從性。群突發期間，於 四個加護病房及三個一般病房共13位住院病人採檢到32株XDRAb。其中7位病人(53.8%) 與外科加護病房有關。分子分型及基因定序確認這32株皆帶ISAba1-blaOxA-51-like及blaOxA-72抗藥基因，證明此群突發為攜有OXA-72及前置ISAba1之類OXA-51 carbapenemase的同型XDRAb散布7個病房。經感控措施確實執行，在未限制carbapenems使用及不關病房下，後續追蹤迄今，無新的群突發。本文報告亞太區首例由產生OXA-72之XDRAb引發的醫院跨病房群突發。雖未找出傳播來源或載體，但顯示在未限制carbapenems使用及不關閉病房下，落實感染控制措施亦可成功遏止全院XDRAb之群突發。