Diphtheria is becoming a prominent issue in Indonesia as its incidence is increasing recently. It also causes various complications, leading to morbidity and mortality. We realized the urgency of fast, reliable, and cheap early detection method for diphtheria infection as one of means necessary for its eradication. Therefore, we created a chimeric between native Escherichia coli Tar chemotaxis receptor and human HB-EGF receptor so the bacterium may recognize diphtheria toxin. Moreover, we combined CheA and CheY in E. coli chemotaxis system with LuxAB and eYFP, respectively. When in contact, LuxAB and eYFP create resonance energy transfer system in which LuxAB gives its emission to eYFP. Without diphtheria toxin, CheA will be in phosphorylated state, allowing interaction with CheY and energy transfer, resulting in yellow color. Toxin binding into chimeric receptor will inhibit CheA phosphorylation, hindering interaction with CheY and energy transfer, resulting in blue color (i.e. LuxAB native color).
Pathogenesis of Diphtheria: How Does Corynebacterium diphtheriae Cause the Disease?
C. diphtheriae is a Gram-positive rod bacterium that causes diphtheria. It produces exotoxin with two fragments (AB toxin). Fragment B facilitates toxin internalization within host cell via endocytosis upon binding with HB-EGF receptor. Endosome internal environment allows catalytic process to split AB toxin into separate fragments, while fragment B forms a pore in endosome membrane, allowing fragment A to be transported into host cell cytoplasm. Fragment A then catalyzes modification of elongation factor 2 (EF-2), thereby attenuates protein synthesis and ultimately killing cell. This process underlies several complications found in patients with diphtheria, such as myocarditis, liver and kidney necrosis. In posterior pharynx, diphtheria infection leads to pseudomembrane formation, which is a local reaction and deposition of dead epithelial cells, bacteria, and immune cells enclosed within fibrin. Large formed pseudomembrane potentially causes respiratory tract obstruction and death.
