Interaction between Naegleria fowleri and pathogenic Escherichia coli by mannose and changes in N. fowleri protease

Naegleria fowleri can cause acute primary amoebic encephalitis. It is known that contact-dependent pathogenicity in free-living amoeba may be mediated through a carbohydrate-dependent pathway. In this study, the effect of mannose on the interaction between N. fowleri and pathogenic Escherichia coli O157:H7 and non-pathogenic E. coli DH5α was analyzed. In particular, the changes in proteases expressed by N. fowleri in response to mannose were analyzed. Unlike the conventional method, mannose was treated with N. fowleri for 1 h. The association between N. fowleri and E. coli O157:H7 treated with 50-mM and 100-mM mannose was significantly reduced by approximately 70.9% and 128.5%, respectively. E. coli O157:H7 invasion was reduced by about 10.8% by 100-mM mannose. Moreover, as a result of culturing N. fowleri invaded by E. coli O157:H7 for 24 h, E. coli O157:H7 also grew about 1.2 times in the group not treated with mannose. E. coli DH5α association was reduced by 25.7% by 100-mM mannose. On the other hand, there was almost no inhibitory effect by 100-mM glucose. In the analysis in which mannose bound to either N. fowleri or bacteria and affected the interaction, there was little effect on the interaction between N. fowleri and bacteria. In zymographic analysis, about 135-kDa and 75-kDa bands were observed by 50-mM and 100-mM mannose, and two bands were significantly increased by 100-mM mannose. This study suggests that mannose can be mediated in the contact-dependent pathway of N. fowleri and will serve as a basis for inducing changes in the protease of N. fowleri by other monosaccharides.