与ISEcp1-like插入序列相关的CTX-M型ESBLs基因传播机制研究

The dissemination of CTX-M-ESBLs associated with ISEcp1-like insertion sequences

目的研究CTX-M-ESBLs在天津地区肺炎克雷伯菌中的传播与ISEcp1-like插入序列及1类整合子的关系。方法采用PCR-mapping、Southern印迹杂交及DNA序列分析等方法检测CTX-M-ESBLs基因,及其与ISEcp1-like插入序列和1类整合子的关系。结果46株产ESBLs肺炎克雷伯菌中44株(95.7%)携带CTX-M-1组和(或)CTX-M-9组基因,未发现CTX-M-2组基因。60%的CTX-M-1组β内酰胺酶基因和73.7%的CTX-M-9组β内酰胺酶基因上游存在ISEcp1-like插入序列。ISEcp1-like插入序列与CTX-M-3及CTX-M-14基因间隔区序列不同。46株中25株(54.3%)携带1类整合子基因,PCR-mapping及Southern印迹杂交未发现CTX-Mβ内酰胺酶基因在整合子上的证据。结论天津地区肺炎克雷伯菌临床株中存在CTX-M-ESBLs的流行,许多CTX-M-ESBLs基因上游存在ISEcp1-like插入序列。ISEcp1-like插入序列可能与CTX-M型超广谱酶基因在天津市肺炎克雷伯菌临床株中的播散有关。

Objective To study the dissemination of CTX-M-ESBLs in clinical isolates of Klebsiella pneumoniae associated with ISEcp1-like insertion sequences as well as class 1 integron. Methods PCR-mapping, Southern blot and DNA sequencing were used to detect blaCTX-M-ESBLs, ISEcp1-like sequences, class 1 integron and analyze their relationship. Results About 95.7% （44/46） of ESBLs-producing isolates were identified to produce enzymes of CTX-M-1 group and/or CTX-M-9 group by PCR. None was identified as CTX-M-2 group. Sixty percent of CTX-M-1 group genes and 73.7% of blaCTX-M-9 group genes were identified at downstream of ISEcp1-like insertion sequences. However, the sequence between ISEcp1-like insertion sequences and blaCTX-M-3 was different from that of blaCTX-M-14. About 54.3% （25/46） of ESBLs-producing isolates carried class 1 integron. No evidence was found that blaCTX-M β-lactamases located in the integrons by PCR-mapping and Southern blot. Conclusions There is prevalence of blaCTX-M β-lactamases among K. pneumoniae in Tianjin. ISEcp1-like insertion sequences were located upstream of many CTX-M β-lactamase genes. It indicates that ISEcp1-like sequences were probably involved in the dissemination of blaCTX-M β-lactamases among clinical isolates of K. pneumoniae in Tianjin.