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目的研究bla_(CTX-M-55)介导的宋内志贺菌#1083的耐药机制。方法双纸片协同扩散法验证#1083是否为产超广谱β-内酰胺酶(ESBL)菌株;PCR方法鉴定其耐药基因;接合转移实验验证携带ESBL基因的质粒是否具有可转移性;VITEK 2仪器检测菌株对多种抗生素的MIC值;基因组测序鉴定介导耐药基因转移的移动元件;引物延伸实验鉴定耐药基因转录起始位点。结果 #1083为bla_(CTX-M-55)介导产ESBL的菌株,携带bla_(CTX-M-55)的耐药质粒可通过接合转移的方式进入受体菌EC600,并使受体菌具有相应的耐药谱;介导bla_(CTX-M-55)转移的转座单元为ISEcp1-bla_(CTX-M-55)-Δorf477,且其上游的插入序列ISEcp1为耐药基因提供强启动子区,促进耐药基因表达,且此表达为恒定表达,不受抗生素的诱导作用影响。结论质粒携带的bla_(CTX-M-55)为#1083的主要耐药基因,插入序列ISEcp1介导此基因的表达与传播。
Objective To study the mechanism of bla_ (CTX-M-55) mediated resistance to Shigella sonnei # 1083. Methods The double-disk synergistic diffusion method was used to confirm whether ESBL-producing strains were ESBL-producing strains. The resistance genes were identified by PCR. The conjugation and transfer experiments confirmed that the plasmid carrying ESBL gene could be transferred. VITEK 2 instrument to detect strains MIC against multiple antibiotics; sequencing of the genomes identifies moving elements that mediate drug resistance gene transfer; and primer extension experiments to identify the transcriptional start site of drug resistance genes. Results # 1083 was ESBL-producing strain bla_ (CTX-M-55). The resistant plasmid carrying bla_ (CTX-M-55) could enter the recipient strain EC600 by conjugation and transfer, (CTX-M-55) -Δorf477, and its upstream insertion sequence ISEcp1 provides a strong promoter for the resistance gene Region, promote the expression of drug resistance gene, and this expression is constant expression, not affected by the antibiotic induction. Conclusion Plasmid-carrying bla_ (CTX-M-55) is the major drug resistance gene of # 1083. The insertion sequence ISEcp1 mediates the gene expression and transmission.