Department of Clinical Laboratory Medicine, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, Japan.
Clin Microbiol Infect. 2013 Feb;19(2):161-8. doi: 10.1111/j.1469-0691.2012.03762.x. Epub 2012 Feb 14.
Plasmid-mediated AmpC β-lactamase-producing Escherichia coli (AmpC-E) bacteraemia was characterized by comparison with bacteraemia caused by extended-spectrum β-lactamase (ESBL)-producing E. coli (ESBL-E) and non-resistant E. coli (NR-E) in the era of the worldwide spread of the CTX-M-15-producing O25b-ST131-B2 clone. Of 706 bloodstream E. coli isolates collected between 2005 and 2010 in three Japanese university hospitals, 111 ESBL screening-positive isolates were analysed for AmpC and ESBL genes by PCR. A case-control study was performed in which the cases consisted of all of the patients with AmpC-E bacteraemia. Phylogenetic groups, sequence types and O25b serotype were determined. Twenty-seven AmpC-E isolates (26 of which were of the CMY-2 type) were identified, and 54 ESBL-E and 54 NR-E isolates were selected for the controls. Nineteen AmpC-E isolates were also positive for ESBL. CTX-M-14 was the most prevalent ESBL type among both the AmpC-E and ESBL-E isolates. The O25b-ST131-B2 clone was the most prevalent among the ESBL-E isolates (26%) and the second most prevalent among the NR-E isolates (13%), but only one O25b-ST131-B2 clone was found among the AmpC-E isolates. Twenty-three different sequence types were identified among the AmpC-E isolates. When compared with bacteraemia with ESBL-E, previous isolation of multidrug-resistant bacteria and intravascular catheterization were independently associated with a lower risk for AmpC-E. When compared with NR-E bacteraemia, prior use of antibiotics was the only significant risk factor for AmpC-E. Unlike the spread of the O25b-ST131-B2 clone between ESBL-E and NR-E, the AmpC-E isolates were not dominated by any specific clone.
在 CTX-M-15 产酶 O25b-ST131-B2 克隆广泛传播的时代，比较质粒介导的 AmpC β-内酰胺酶产大肠埃希菌（AmpC-E）菌血症与产超广谱β-内酰胺酶（ESBL）大肠埃希菌（ESBL-E）和非耐药大肠埃希菌（NR-E）菌血症的特征。在 2005 年至 2010 年间，从三家日本大学医院采集的 706 株血流大肠埃希菌分离株中，对 111 株 ESBL 筛选阳性分离株进行了 AmpC 和 ESBL 基因的 PCR 分析。对 AmpC-E 菌血症患者进行病例对照研究，其中病例均为 AmpC-E 菌血症患者。确定了进化群、序列类型和 O25b 血清型。鉴定出 27 株 AmpC-E 分离株（其中 26 株为 CMY-2 型），选择 54 株 ESBL-E 和 54 株 NR-E 分离株作为对照。19 株 AmpC-E 分离株也对 ESBL 呈阳性。CTX-M-14 是 AmpC-E 和 ESBL-E 分离株中最常见的 ESBL 类型。O25b-ST131-B2 克隆在 ESBL-E 分离株中最为流行（26%），在 NR-E 分离株中为第二大流行（13%），但在 AmpC-E 分离株中仅发现一个 O25b-ST131-B2 克隆。AmpC-E 分离株中有 23 种不同的序列类型。与 ESBL-E 菌血症相比，既往分离出的多药耐药菌和血管内导管与 AmpC-E 菌血症的风险较低独立相关。与 NR-E 菌血症相比，抗生素的使用是 AmpC-E 的唯一显著危险因素。与 O25b-ST131-B2 克隆在 ESBL-E 和 NR-E 之间的传播不同，AmpC-E 分离株不受任何特定克隆的支配。
