Antibiotic Resistance Monitoring & Reference Laboratory, HPA-Colindale, 61 Colindale Avenue, London NW9 5EQ, UK.
J Antimicrob Chemother. 2012 Apr;67(4):878-85. doi: 10.1093/jac/dkr553. Epub 2011 Dec 29.
To characterize plasmids encoding extended-spectrum β-lactamases (ESBLs) from a recent UK collection of clinical Escherichia coli isolates.
The isolates comprised 118 ESBL producers referred from 54 laboratories. Plasmids were transferred by electroporation, and their incompatibility groups, associated addiction systems and resistance genes with the flanking genetic environments were identified by PCR or sequencing.
Seventy isolates had plasmids encoding CTX-M-15 (n = 53), CTX-M-14 (n =9), CTX-M-27 (n = 1), CTX-M-3 (n = 2) and SHV-12 (n = 5) ESBLs that were transformable; non-transformable ESBLs were mainly CTX-M enzymes (42/48). Most transformable bla(CTX-M-15) genes (43/53) were harboured on single replicon or multireplicon IncF plasmids, with IncFIA4-FIB1-FII31 (n = 11) and IncFIA1-FII2 (n = 15) being most frequent; the latter included eight pEK499 plasmids, typical of UK epidemic strain A. Plasmids harbouring bla(CTX-M-14) belonged variously to IncF, IncI1 and IncHI2 types, and 16 encoding CTX-M or SHV enzymes were non-typeable. Only IncF plasmid types carried the addiction systems sought and those with bla(CTX-M-15) frequently harboured bla(OXA-1) and aac(6')-Ib-cr, and often transferred trimethoprim and tetracycline resistance; those with bla(CTX-M-14) encoded trimethoprim, sulphonamide, streptomycin and tetracycline resistance. Most ESBL genes were associated with the well-known mobile elements ISEcp1 and IS26, but nearly half (23/55) of the ISEcp1 sequences upstream of bla(CTX-M-15) were interrupted by an IS26 at various positions.
Most ESBLs (70/118) were encoded by transformable plasmids, although a sizable minority could not be transformed. The majority of transformable plasmids (51/70; 72.9%) were diverse multiresistant IncF types possessing multiple addiction systems. The spread of bla(CTX-M-15) can be attributed not just to clonal expansion, but also to the horizontal dissemination of related plasmids.
对最近从英国收集的临床大肠埃希菌分离株中携带的扩展谱β-内酰胺酶（ESBLs）的质粒进行特征描述。
这些分离株包括 118 株由 54 个实验室送检的 ESBL 产生菌。通过电穿孔将质粒转移，然后通过 PCR 或测序鉴定其不相容群、相关附加系统和耐药基因及其侧翼遗传环境。
70 株分离株的质粒可编码 CTX-M-15（n=53）、CTX-M-14（n=9）、CTX-M-27（n=1）、CTX-M-3（n=2）和 SHV-12（n=5）ESBLs，这些质粒具有可转移性；不可转化的 ESBL 主要为 CTX-M 酶（n=42/48）。大多数可转化的 bla（CTX-M-15）基因（n=43/53）位于单个复制子或多复制子 IncF 质粒上，其中 IncFIA4-FIB1-FII31（n=11）和 IncFIA1-FII2（n=15）最为常见；后者包括 8 个典型的英国流行株 A 的 pEK499 质粒。携带 bla（CTX-M-14）的质粒属于 IncF、IncI1 和 IncHI2 型，16 个编码 CTX-M 或 SHV 酶的质粒不可分型。仅 IncF 质粒类型携带所寻找的附加系统，带有 bla（CTX-M-15）的质粒常带有 bla（OXA-1）和 aac（6'）-Ib-cr，且常可转移对甲氧苄啶和四环素的耐药性；带有 bla（CTX-M-14）的质粒则编码对甲氧苄啶、磺胺类药物、链霉素和四环素的耐药性。大多数 ESBL 基因与著名的移动元件 ISEcp1 和 IS26 相关，但 bla（CTX-M-15）上游的近一半（n=23/55）ISEcp1 序列在不同位置被 IS26 中断。
大多数 ESBLs（n=118）由可转化的质粒编码，但少数不能转化。大多数可转化质粒（n=70/70；72.9%）是具有多种附加系统的多样化的多耐药性 IncF 型。bla（CTX-M-15）的传播不仅归因于克隆扩张，还归因于相关质粒的水平传播。
