疑似Kluyvera ascorbata院內感染的實驗室調查

Laboratory Investigation of Suspected a Nosocomial Infection of Kluyvera ascorbata

在南台灣的某家區域醫院，在2014年3月及4月自入住相同加護病房的不同病患各分離出一株Kluyvera ascorbata，因為此醫院以前不曾分離這株細菌，因此展開院內群突發的調查。脈衝式電泳分析法（pulsed-field gel electrophoresis；PFGE）的結果顯示這二株細菌並不是相同的菌株，因此排除院內群突發。抗生素敏感性試驗結果顯示一株（K1）對cefazolin、cefuroxime及ceftriaxone具有抗藥性，但是另一株（K2）只有對cefazolin具有抗藥性。聚合酶連鎖反應（polymerase chain reaction，PCR）及基因序列分析（sequence analysis）顯示K1及K2都帶有CTX-M-like基因，但是沒有發現其他β-lactamase基因。質體電泳及南方墨點法（southern blot）顯示CTX-M-like基因位於染色體上。聚合酶連鎖反應及基因序列分析顯示K1的OmpC基因與K2的OmpF基因存在突變。在此，我們仍然強烈建議假如實驗室接續分離出相同的罕見菌種，特別是臨床檢體來自相同的醫療單位，一定要高度的懷疑院內群突發已經發生的可能性，並展開群突發調查。

At a regional hospital in southern Taiwan, two strains of Kluyvera ascorbata were isolated among two different patients in the same intensive care unit in March and April 2014, respectively. Because this strain was not isolated in this hospital before, laboratory investigation of suspected an outbreak was done. The result of pulsed-field gel electrophoresis revealed the two strains were different strain; hence, an outbreak was ruled out. Antimicrobial susceptibility testing revealed one strain (K1) was resistant to cefazolin, cefuroxime and ceftriaxone; another strain (K2) was only resistant to cefazolin. Polymerase chain reaction (PCR) and sequence analysis revealed both K1 and K2 had CTX-M-like genes, but no other β-lactamase gene was found. Plasmid electrophoresis and Southern blot revealed CTX-M-like genes were on chromosome. PCR and sequence analysis revealed the mutation was present in OmpC genes of K1 and OmpF genes in K2. Herein, we still highly suggested that if clinical laboratory detect successively rare organisms of the same species, especially the clinical samples came from the same medical unit, a non-socomial outbreak should be highly suspected, and an investigation of outbreak should be implemented.