V型分泌系统(T5SS)在禽致病性大肠杆菌中的分布及流行情况

Distribution and epidemiological analysis of type V secretion system (T5SS) in avian pathogenic Escherichia coli

摘要:

【背景】禽致病性大肠杆菌(Avian pathogenic Escherichia coli，APEC)可引起禽的大肠杆菌病，严重危害养禽业。V型分泌系统(type V secretion system，T5SS)在APEC感染过程中发挥重要作用。【目的】分析不同致病型大肠杆菌的T5SS在APEC中的分布规律，探讨T5SS与APEC的大肠杆菌进化分群及其他毒力因子的关联性。【方法】根据大肠杆菌的15个T5SS序列设计特异性引物，采用PCR检测T5SS在APEC临床分离株中的分布；分析APEC菌株的系统进化分群及毒力因子分布，探讨T5SS分布和APEC系统进化分群及毒力因子的相关性。【结果】T5SS在APEC临床分离株中广泛分布，其中ydeK和pplfP的分布率最高，分别为98.55%和92.03%；而upaC和pic的分布率均低于10%。系统进化分群结果显示，APEC主要属于A、B1和D进化分群，B2群较少；T5SS分布和进化分群分析发现ehaA、ehaB、pic、vat在D进化分群APEC菌株中分布率较高，而ehaG、ag43/flu、apaC主要分布于A及B1群APEC中。然而，T5SS和APEC其他毒力基因分布无明显的关联性。【结论】T5SS广泛存在于APEC分离株中，且部分T5SS分布与大肠杆菌系统进化分群存在关联性。

Abstract:

[Background] Systemic infections caused by avian pathogenic Escherichia coli (APEC) are economically devastating to poultry industries worldwide. Type V secretion system (T5SS) plays an important role during the infection of APEC. [Objective] This study was carried out to analyze the distribution of T5SS in APEC and its correlation with E. coli phylogenetic group and other virulence factors. [Methods] The 15 E. coli T5SS were selected for primers designing, and the distribution of these T5SS in APEC clinical isolates were detected by PCR. The phylogenetic group and virulence factor of APEC strains were determined. The correlations between T5SS distribution and phylogenetic group and other virulence factors of APEC were analyzed. [Results] T5SS was widely distributed in APEC isolates. T5SS ydeK and pplfP was present in 98.55% and 92.03% of the APEC isolates, respectively. However, the distribution rates of T5SS upaC and pic in APEC were less than 10.00%. Most APEC isolates belonged to A, B1 and D phylogenetic groups, following by B2. The combinations analysis showed that T5SS ehaA, ehaB, pic and vat were predominated present in phylogenetic group D APEC isolates. While, the phylogenetic groups A and B1 were the predominated groups that harbor the ehaG, ag43/flu and apaC. However, no significant correlation between the distribution of T5SS and other virulence genes in APEC were found. [Conclusion] T5SS is widely distributed in APEC, and some T5SS was correlated with the phylogenetic group of APEC.