四种K:CA荚膜型别克罗诺杆菌的荚膜多糖组分研究

Capsular polysaccharide components from four K:CA capsular types of Cronobacter

摘要:

【目的】克罗诺杆菌(Cronobacter)是一类以奶粉为主要传播媒介的食源性致病菌，能够引起坏死性小肠结肠炎、脑膜炎、菌血症等疾病。荚膜是细菌常见的毒力因子，本研究对4种K:CA型别的Cronobacter荚膜多糖进行分析，以期发现荚膜型别与荚膜多糖的单糖组成的关联规律。【方法】本研究通过苯酚-硫酸法和氢核磁共振(¹H NMR)分别对28株Cronobacter (4种K:CA型别)荚膜多糖的产量和单糖组成进行分析。【结果】文章研究了不同培养基、培养时间对Cronobacter荚膜多糖产生的影响，确定了最佳培养条件为在牛奶琼脂培养基中培养48.0 h，而且不同条件下未改变Cronobacter荚膜多糖的单糖组成。本研究进一步发现，4种K:CA型别菌株间的荚膜多糖产量具有显著差异，K2:CA2型别的荚膜多糖平均产量最高。其中，2株荚膜多糖产量高的菌株C. sakazakii ATCC 12868和C. sakazakii ATCC 29004也均为K2:CA2型别，产量分别为19.6%和28.4%。此外，通过¹H NMR测定出28株Cronobacter的荚膜多糖中的单糖组分有8种，其中在C. malonaticus cro1754B2和C. sakazakii cro1573B3发现了β-ManpNAc，只在C. sakazakii cro771A2中发现了β-Ribp，本研究还发现大多数K1:CA1型别荚膜多糖中均有α-Rhap，大部分K1:CA2型别和K2:CA1菌株荚膜多糖由β-Glcp构成，其中α-Glcp为K2:CA2荚膜多糖的主要单糖组分。【结论】本研究初步揭示了4种荚膜型别Cronobacter的多糖分泌规律，发现K2:CA2型别的荚膜多糖平均产量最高，发现了Cronobacter荚膜多糖的单糖组成与荚膜型别的相关性，为Cronobacter的荚膜特性深入研究奠定了理论和技术基础。

关键词:克罗诺杆菌;荚膜多糖;氢核磁共振(¹H NMR);荚膜型别

Abstract:

[Objective] Cronobacter, a foodborne pathogen transmitted mainly by powdered infant formula, can cause necrotizing enterocolitis, bacteraemia, meningitis and other diseases. We analyzed the composition of capsular polysaccharides from four K:CA types of Cronobacter to explore the correlation between different capsular types and monosaccharide composition of capsular polysaccharides. [Methods] We measured the yields of capsular polysaccharides from 28 Cronobacter strains (4 K:CA types) by phenol-sulfuric acid method and determined the monosaccharide composition of the capsular polysaccharides by ¹H NMR. [Results] The capsular polysaccharide yield of Cronobacter was the best when the bacteria were cultured in milk agar for 48.0 h, while the monosaccharide composition did not change under different culture conditions. The yield of capsular polysaccharides varied among the four K:CA types of Cronobacter, of which the K2:CA2 type had the highest average yield. Further, we identified that two strains C. sakazakii ATCC 12868 and C. sakazakii ATCC 29004 with high yields of capsular polysaccharides (19.6% and 28.4%, respectively) were of K2:CA2 type. The capsular polysaccharides of 28 Cronobacter isolates contained 8 monosaccharides, among which β-ManpNAc was only in C. malonaticus cro1754B2 and C. sakazakii cro1573B3, and β-Ribp only in C. sakazakii cro771A2. In addition, α-Rhap, β-Glcp, and α-Glcp were the dominant monosaccharide components of capsular polysaccharide in strains of K1:CA1 type, K1:CA2 and K2:CA1 types, and K2:CA2 type, respectively. [Conclusion] This study preliminarily revealed the polysaccharide yields of four K:CA capsular types of Cronobacter and found that K2:CA2 type had the highest average yield of capsular polysaccharide. We confirmed the correlation between the monosaccharide composition of capsular polysaccharide and the capsular types of Cronobacter, which provided a theoretical and technical foundation for further research on the capsular properties of Cronobacter.

Key words:Cronobacter spp.;capsular polysaccharide;¹H NMR;capsular types