背景：
呼吸机相关性肺炎（VAP）是一种常见的医院感染，与多药耐药（MDR）病原体引起的高发病率相关。这项研究的目的是确定超广谱β-内酰胺酶（ESBL）基因，特别是bla CTX-M-15，在肺炎克雷伯菌（K.pneumoniae）相关的VAP中的发生，并研究抗菌药物的抗药性模式和分子肺炎克雷伯菌的流行病学特征。

材料和方法：
从2013年1月至2015年12月，我们回顾性地收集了来自中国三级医院的89株引起VAP的肺炎克雷伯菌分离株，其中评估了产ESBL菌株的抗菌药物敏感性。研究了几种在产生ESBL的肺炎克雷伯菌分离株中临床相关的抗生素抗性基因。聚合酶链反应（PCR）和DNA测序用于表征bla CTX-M-15的遗传背景。通过交配获得携带bla CTX-M-15的缀合质粒，并进一步进行复制子分型。通过脉冲场凝胶电泳（PFGE）和多位点序列分型评估分离株的遗传相关性。

结果：
所有产生ESBL的30株分离株均显示出MDR表型，分别在21,21,1和20株分离株中检测到bla SHV，bla CTX-M，bla OXA和bla TEM。 bla CTX-M-15是最普遍的ESBL基因（19 / 30,63.33％），并且在15个bla CTX-M-15基因上游48bp处检测到ISEcp1。基于S1-PFGE分析，25个分离物显示出不同的质粒谱，范围为约70至320kb。具有bla TEM和qnr基因的bla CTX-M-15和来自8个分离物的ISEcp1元件通过缀合可共转移至受体，IncFIB，IncFIC和IncFII是最普遍的复制子。鉴定了20种不同的PFGE模式和11种序列类型，ST304占优势。

结论：
这项工作报告了bla CTX-M-15在中国肺炎克雷伯氏菌引起的VAP中的出现。我们显示携带bla CTX-M-15与bla TEM，qnr抗性基因和ISEcp1元件的IncFIB，IncFIC和/或IncFII质粒介导肺炎克雷伯氏菌相关VAP的局部流行。

BACKGROUND:
Ventilator-associated pneumonia (VAP) is a common nosocomial infection associated with high morbidity due to multidrug-resistant (MDR) pathogens. The purpose of this study was to determine the occurrence of extended-spectrum β-lactamase (ESBL) genes, especially bla CTX-M-15, in Klebsiella pneumoniae (K. pneumoniae)-associated VAP and to investigate the antimicrobial resistance patterns and molecular epidemiological characteristics of K. pneumoniae strains.

MATERIALS AND METHODS:
From January 2013 to December 2015, we retrospectively collected 89 VAP-causing K. pneumoniae isolates from tertiary-care hospitals in China, among which ESBL-producing strains were assessed for antimicrobial susceptibility. Several antibiotic resistance genes of clinical relevance in K. pneumonia isolates producing ESBL were investigated. Polymerase chain reaction (PCR) and DNA sequencing were employed to characterize the genetic contexts of bla CTX-M-15. Conjugative plasmids carrying bla CTX-M-15 were obtained by mating and further subjected to replicon typing. The genetic relatedness of isolates was assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing.

RESULTS:
All of the 30 ESBL-producing isolates identified displayed MDR phenotype, with bla SHV, bla CTX-M, bla OXA, and bla TEM detected in 21, 21, 1, and 20 isolates, respectively. bla CTX-M-15 was the most prevalent ESBL gene (19/30, 63.33%), and ISEcp1 was detected 48 bp upstream of 15 bla CTX-M-15 genes. Based on S1-PFGE analyses, 25 isolates exhibited different plasmid profiles, ranging from ~70 to 320 kb. The bla CTX-M-15 with bla TEM and qnr genes and the ISEcp1 element from eight isolates were co-transferrable to recipients via conjugation, with IncFIB, IncFIC, and IncFII being the most prevalent replicons. Twenty different PFGE patterns and 11 sequence types were identified, with ST304 being dominant.

CONCLUSION:
This work reports the emergence of bla CTX-M-15 in K. pneumoniae-induced VAP in China. We showed that IncFIB, IncFIC, and/or IncFII plasmids carrying bla CTX-M-15 with bla TEM, qnr resistance genes, and the ISEcp1 element mediate the local prevalence in K. pneumoniae-associated VAP.

https://www.ncbi.nlm.nih.gov/pubmed/30588046