背景
肠外致病性大肠杆菌（ExPEC）是一种重要的细菌，可导致许多血流感染，包括尿路感染甚至致命的菌血症。本研究的目的是研究从土耳其血培养物中分离的ExPEC菌株是否与基于16S rRNA的系统发育簇和抗生素抗性谱，毒力因子或克隆谱系之间存在关联。

方法
表型鉴定的ExPEC血培养分离物（n = 104）包括在该研究中。进行16S rRNA部分序列分析以进行ExPEC分离株的基因型鉴定。进行抗生素敏感性和分离物的超广谱β-内酰胺酶测试。系统发育分类（A，B1，B2和D），多基因座序列分型和毒力相关基因进行了研究。

结果
基于16S rRNA部分序列分析，104个（93.26％）ExPEC分离株中的97个被确认为大肠杆菌。氨苄青霉素（74.22％）和头孢呋辛酯（65.97％）的耐药率在ExPEC分离株中最高。在ExPEC的系统发育分类方面，D（38.14％，37/97）是A（29.89％，29/97），B2（20.61％，20/97）和B1（11.34％，11）之后最常见的群体。 / 97）。通过Multi Locus Sequence Typing分析属于B2系统发育组的20个ExPEC分离株的序列类型。 20个中的10个分离株（50.0％）被鉴定为ST131。其他ST是ST95（n = 1），ST14（n = 1），ST10（n = 1），ST69（n = 1），ST1722（n = 2），ST141（n = 1），ST88（n = 1），ST80（n = 1）和ST998（n = 1）。在ST131菌株中，六个（60％，6/10）代表血清群O25。最常见的毒力因子基因是血清抗性因子基因，traT（55.7％）aerobactin铁载体受体和yersiniabactin编码基因iutA（45.3％）和fyuA（50.5％）。此外，PAI（41.2％），iroN（23.7％），hlyA（15.4％），kpsII（13.4％），ompT（13.4％），papG（12.4％），iss（9.3％），cnf1（7.2％） ，ibeA（2.06％）和sfaS（2.06％）基因存在于ExPEC分离株中。

结论
基于16S rRNA的系统发育关系树分析显示97个ExPEC分离株中存在大的簇以及相关的参考菌株。有21个主要集群，32个密切相关的子集群。根据我们的研究结果，ExPEC的不同克隆谱系可以显示出不同的抗生素敏感性和毒力特性。我们还得出结论，根据系统发育组（A，B1，B2和D），毒力因子没有分布。属于相同系统发育组和序列类型的ExPEC分离株可显示不同的抗性和毒力特征。

Background
Extraintestinal pathogenic Escherichia coli (ExPEC) is an important bacterium and responsible for many bloodstream infections, including urinary tract infections and even fatal bacteremia. The aim of this research was to investigate whether ExPEC strains isolated from Turkish blood cultures have a relationship between 16S rRNA based phylogenetic clusters and antibiotic resistance profiles, virulence factors or clonal lineages.

Methods
Phenotypically identified ExPEC blood culture isolates (n = 104) were included in this study. The 16S rRNA partial sequence analysis was performed for genotypic identification of ExPEC isolates. Antibiotic susceptibility and Extended-Spectrum β-Lactamase testing of isolates were performed. Phylogenetic classification (A, B1, B2 and D), Multi Locus Sequence Typing analysis and virulence-associated genes were investigated.

Results
Based on 16S rRNA partial sequence analysis, 97 out of 104 (93.26%) ExPEC isolates were confirmed as E. coli. Ampicillin (74.22%) and cefuroxime axetil (65.97%) resistances had the highest frequencies among the ExPEC isolates. In terms of phylogenetic classification of ExPEC, D (38.14%, 37/97) was the most prevalent group after A (29.89%, 29/97), B2 (20.61%, 20/97), and B1 (11.34%, 11/97). The sequence types of the 20 ExPEC isolates belonging to the B2 phylogenetic group were analyzed by Multi Locus Sequence Typing. Ten isolates out of 20 (50.0%) were identified as ST131. The other STs were ST95 (n = 1), ST14 (n = 1), ST10 (n = 1), ST69 (n = 1), ST1722 (n = 2), ST141 (n = 1), ST88 (n = 1), ST80 (n = 1), and ST998 (n = 1). Of the ST131 strains, six (60%, 6/10) represented serogroup O25. The most common virulence factor genes were serum resistance factor gene, traT (55.7%) aerobactin siderophore receptor and yersiniabactin encoding genes iutA (45.3%) and fyuA (50.5%), respectively. In addition, PAI (41.2%), iroN (23.7%), hlyA (15.4%), kpsII (13.4%), ompT (13.4%), papG (12.4%), iss (9.3%), cnf1 (7.2%), ibeA (2.06%), and sfaS (2.06%) genes were present in the ExPEC isolates.

Conclusion
The 16S rRNA-based phylogenetic relationship tree analysis showed that a large cluster was present among 97 ExPEC isolates along with related reference strains. There were 21 main clusters with 32 closely related subclusters. Based on our findings, different clonal lineages of ExPEC can display different antibiotic susceptibilities and virulence properties. We also concluded that virulence factors were not distributed depending on phylogenetic groups (A, B1, B2, and D). The ExPEC isolates belonging to the same phylogenetic group and sequence type could display different resistance and virulence characteristics.

https://peerj.com/articles/5470/?utm_source=TrendMD&utm_campaign=PeerJ_TrendMD_1&utm_medium=TrendMD