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

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.