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首页> 外文期刊>Infection and immunity >Prevalence of Virulence Genes and Clonality inEscherichia coli Strains That Cause Bacteremia in Cancer Patients
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Prevalence of Virulence Genes and Clonality inEscherichia coli Strains That Cause Bacteremia in Cancer Patients

机译：致癌患者细菌血症的大肠杆菌株中毒力基因和克隆的普遍性

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Phenotypic analysis of Escherichia coli strains causing bacteremia in cancer patients suggests that they possess specific virulence properties. To investigate this hypothesis, we compared the frequency of the virulence-related genes cnf1,cnf2, papC, hlyC, andiut in 155 E. coli strains isolated from hospitalized cancer patients with epidemiologically unrelated cases of bacteremia to their frequency in 70 E. coli strains isolated from the feces of healthy unrelated volunteers. Of the blood isolates, 24, 37, and 26% were positive for cnf1,papC, and hlyC, respectively, versus only 6, 17, and 6% of the fecal isolates (P iut gene. The patients' clinical characteristics did not significantly influence these frequencies. The presence on various pathogenicity islands (PAIs) of a combination of the cnf1,papC, and hlyC genes on the chromosome was strongly suggested by Southern blotting of pulsed-field gel electrophoresis (PFGE) patterns with specific DNA probes. The phylogenetic relatedness among 60 strains carrying three, two, one, or no virulence genes and 6 ECOR strains included as references was determined by neighbor joining, the unweighted pair-group method with arithmetic mean, and Wagner analysis of the randomly amplified polymorphic DNA (RAPD) patterns generated by 11 primers. Identification of a major cluster including 96.4% of the strains carrying thecnf1, papC, and hlyC genes and ECOR subgroup B2 strains suggested that the virulent E. colistrains causing bacteremia in cancer patients are closely related to ECOR B2 strains. The presence in the E. coli population surveyed of a strong linkage disequilibrium, and especially of a highly significant correlation between PFGE and RAPD genetic distances, confirms that clonal propagation has a major impact on the E. coli population structure. Nevertheless, low bootstrap values in the phylogenetic tree suggested that frequent genetic exchange inhibits the individualization of discrete genetic lineages, which are stable on an evolutionary scale.
机译：对在癌症患者中引起菌血症的大肠杆菌菌株的表型分析表明，它们具有特定的毒力特性。为了研究该假设，我们比较了从流行病学无关的住院患者中分离出的155株大肠杆菌中与毒力相关的基因cnf1，cnf2，papC，hlyC和andut的频率与在70株大肠杆菌中分离的频率与健康无关的志愿者的粪便隔离。在这些血液分离物中，cnf1，papC和hlyC分别为24％，37％和26％，而粪便分离物中只有6％，17％和6％（P iut基因）。患者的临床特征确实脉冲场凝胶电泳（PFGE）的Southern印迹和特异性DNA探针强烈提示染色体上cnf1，papC和hlyC基因的组合存在于各种致病岛（PAI）上。通过邻居连接，算术平均值的非加权成对组方法和随机扩增的多态性DNA的Wagner分析，确定了60个带有3个，2个，1个或没有毒力基因的毒株和6个ECOR毒株作为参照的系统发育相关性。 （RAPD）模式由11条引物产生，鉴定出一个主要簇，包括96.4％的携带cnf1，papC和hlyC基因的菌株以及ECOR B2亚型菌株，表明强毒的大肠杆菌癌症患者的ng菌血症与ECOR B2菌株密切相关。在调查的大肠杆菌种群中，存在很强的连锁不平衡，尤其是PFGE和RAPD遗传距离之间存在高度显着的相关性，这证实了克隆繁殖对大肠杆菌种群结构具有重大影响。尽管如此，系统发育树中的自举值较低，表明频繁的遗传交换会抑制离散遗传谱系的个体化，而这些遗传谱系在进化规模上是稳定的。

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