血流感染肺炎克雷伯菌中CRISPR-Cas系统的分布及其与毒力基因和耐药的关系

目的了解血流感染肺炎克雷伯菌中CRISPR-Cas系统的分布特征并分析其与毒力基因和耐药的关系。方法收集非重复血流感染肺炎克雷伯菌248株,使用Vitek2-Compact全自动微生物分析系统进行菌株鉴定及药物敏感性分析,PCR检测CRISPR-Cas系统3个相关基因(CRISPR1、CRISPR2和cas1)、筛查6种常见高毒力荚膜血清型(K1、K2、K5、K20、K54和K57)、12种毒力基因及检测13种耐药基因,用x”检验比较携带有CRISPR-Cas系统菌株与不携带CRISPR-Cas系统菌株毒力及耐药差异。结果CRISPR-Cas系统的检出率为29.8%(74/248);K1型是携带CRISPR-Cas系统肺炎克雷伯菌的主要荚膜血清型,占28.4%(21/74);除kpn基因外,携带CRISPR-Cas系统菌株的毒力基因检出率均大于不携带CRISPR-Cas系统菌株,其中7种差异有统计学意义;除对氨苄西林耐药率达100%外,携带有CRISPR-Cas系统菌株的其他抗菌药物耐药率均小于不携带有CRISPR-Cas系统菌株,其中13种差异有统计学意义;携带CRISPR-Cas系统菌株的耐药基因阳性率小于不携带CRISPR-Cas系统的菌株,且blape、blasy、qnrS基因差异有统计学意义。结论高毒力荚膜血清型肺炎克雷伯菌中主要为K1型携带CRISPR-Cas系统,携带CRISPR-Cas系统的肺炎克雷伯菌相对于不携带CRISPR-Cas系统菌株的毒力基因阳性率高,耐药率低,耐药基因的阳性率低。CRISPR-Cas系统可能能降低耐药基因在肺炎克雷伯菌中的水平传播,尤其是在K1型肺炎克雷伯菌。

Distribution of the CRISPR-Cas system in Klebsiella pneumoniae strains isolated from blood samples and its relationship with virulence genes and resistance

Objective To understand the distribution of the CRISPR-Cas system in Klebsiella pneumoniae strains isolated from blood samples and its relationship with virulence genes and resistance. Methods Two hundreds and forty-eight K. pneumoniae strains were collected from blood samples. The strains were identifiey using Vitek2-compact automatic microorganisms analysis system, and the drug susceptibility was analyzed. All the isolates were assessed for three CRISPR-Cas systee related genes, six hypervirulent capsular serotypes, twelve virulence genes, and thirteen resistant genes by PCR. The virulence and drug resistance between CRISPR-Cas+ strains and CRISPR-Cas- were compared by chi-square tests. Results The positive rate of the CRISPR-Cas systes was 29.8% (74/248). K1-kps was the major capsule serotype of Klebsiella pneumoniae carrying the CRISPR-Cas system, accounting for28.4% (21/74). Except for kpn gene, the positive rates of virulence genes carrying the CRISPR-Cas system strains were larger than those without the CRISPR-Cas system strains, of which seven types of differences were statistically significant. Except for ampicillin intrinsic resistance, the resistance rates of other antimicrobials carrying the CRISPR-Cas system strains were smaller than those without the CRISPR-Cas system strains, of which 13 types of differences were statistically significant. The positive rate of drug resistance genes carrying the CRISPR-Cas system was smaller than that of the strains that did not carry the CRISPR-Cas system, and the differences of KPC, SHV, and qnrS genes were statistically significant. Conclusions Hypervirulent Klebsiella pneumoniae carrying CRISPR-Cas systes was K1-kpn. The Klebsiella pneumoniae carrying the CRISPR-Cas systes had a higher positive rate of the virulence gene, a lower resistance rate and a lower rate of drug resistance genes than that didn’t carry the CRISPR/Cas system strain. The CRISPR-Cas systey might reduce the horizontal transference of drug resistance genes in Klebsiella pneumoniae, especially in