Laboratory of Microbiology, Department of Clinical Laboratories, Centro Médico San Joaquín, Escuela de Medicina, Pontificia Universidad Católica de Chile, 3rd floor, Vicuña Mackenna, 4686, Santiago, Chile.
Clinical Laboratories Network, Red de Salud UC-CHRISTUS, Santiago, Chile.
BMC Microbiol. 2021 Apr 9;21(1):107. doi: 10.1186/s12866-021-02169-3.
Klebsiella pneumoniae is the most frequent KPC-producing bacteria. The bla gene is frequently embedded in Tn4401 transposon, and less frequently in non-Tn4401 elements (NTE) variants I-III. The first case of KPC in the UC-CHRISTUS Clinical Hospital was detected in Pseudomonas aeruginosa. Soon after this event, KPC was detected in 2 additional Pseudomonas aeruginosa, 3 Escherichia coli, 3 Enterobacter cloacae, 3 Klebsiella pneumoniae, and 1 Citrobacter freundii, isolated from 6 different patients. We aimed to elucidate the possible mechanisms of genetic transfer and dissemination of the bla gene among isolates of this multispecies outbreak. A molecular epidemiology analysis of the above mentioned clinical isolates (n = 13) through Multi-Locus Sequence Typing, plasmid analysis, Pulsed-Field Gel-Electrophoresis, and Whole-genome sequencing (WGS) was performed.
High-risk sequence types were found: K. pneumoniae ST11, P. aeruginosa ST654, and E. cloacae ST114. All enterobacterial isolates were not clonal except for 3 E. coli isolated from the same patient. WGS analysis in 6 enterobacterial isolates showed that 4 of them had bla embedded in a novel variant of NTE designated NTE-IIe. Upstream of bla gene there was a 570 pb truncated bla gene followed by an insertion sequence that was 84% similar to ISEc63, a 4473 bp element of the Tn3 family. Downstream the bla gene there was a truncated ISKpn6 gene, and the inverted repeat right sequence of Tn4401. The ISec63-like element together with the bla gene plus Tn4401 remnants were inserted in the Tra operon involved in conjugative transfer of the plasmid. This NTE was carried in a broad host-range IncN plasmid. P. aeruginosa isolates carried bla gene embedded in a typical Tn4401b transposon in a different plasmid, suggesting that there was no plasmid transfer between Enterobacteriaceae and P. aeruginosa as initially hypothesized.
Most enterobacterial isolates had bla embedded in the same NTE-IIe element, suggesting that this multispecies KPC outbreak was due to horizontal gene transfer rather than clonal spread. This poses a greater challenge to infection control measures often directed against containment of clonal spread.
肺炎克雷伯菌是最常见的产 KPC 细菌。bla 基因通常嵌入 Tn4401 转座子中，较少嵌入非 Tn4401 元件（NTE）变体 I-III。UC-CHRISTUS 临床医院的首例 KPC 是在铜绿假单胞菌中发现的。在此事件发生后不久，又在 2 株铜绿假单胞菌、3 株大肠埃希菌、3 株阴沟肠杆菌、3 株肺炎克雷伯菌和 1 株弗氏柠檬酸杆菌中检测到 KPC，这些菌株均来自 6 名不同的患者。我们旨在阐明 bla 基因在该多物种暴发的分离株中遗传转移和传播的可能机制。通过多位点序列分型、质粒分析、脉冲场凝胶电泳和全基因组测序（WGS）对上述临床分离株（n=13）进行分子流行病学分析。
发现高风险序列类型：肺炎克雷伯菌 ST11、铜绿假单胞菌 ST654 和阴沟肠杆菌 ST114。除了 3 株来自同一患者的大肠埃希菌外，所有肠杆菌分离株均不是克隆的。6 株肠杆菌分离株的 WGS 分析显示，其中 4 株 bla 嵌入一种新型 NTE，命名为 NTE-IIe。bla 基因上游是一个 570bp 的截断 bla 基因，其后是一个插入序列，与 Tn3 家族的 4473bp 元件 ISEc63 有 84%的相似性。bla 基因下游是一个截断的 ISKpn6 基因和 Tn4401 的反向重复右序列。ISec63 样元件与 bla 基因加 Tn4401 残余物一起插入参与质粒接合转移的 Tra 操纵子中。该 NTE 位于广泛宿主范围的 IncN 质粒中。铜绿假单胞菌分离株携带 bla 基因，嵌入另一种质粒中的典型 Tn4401b 转座子，表明最初假设的肠杆菌科和铜绿假单胞菌之间没有质粒转移。
大多数肠杆菌分离株的 bla 基因嵌入相同的 NTE-IIe 元件中，提示该多物种 KPC 暴发是由于水平基因转移而不是克隆传播引起的。这对感染控制措施构成了更大的挑战，这些措施通常针对遏制克隆传播。
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