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Intracellular viability of toxigenic Corynebacterium diphtheriae strains in HEp-2 cells
Raphael Hirata1, Fátima Napoleão, Luiz Henrique Monteiro-Leal
1Disciplina de Microbiologia e Imunologia, Faculdade de Ciências Médicas, Universidade do Estado do Rio de Janeiro, Av. 28 de Setembro 87, Fundos, 3 degrees andar., P.O. Box 20 551-030, Vila Isabel, Rio de Janeiro, RJ, Brazil.
Abstract:
Corynebacterium diphtheriae, generally considered an extracellular coloniser, was evaluated for its ability to enter and survive within HEp-2 monolayers by gentamicin protection assay. Intracellular viability of HC01 strain, isolated from endocarditis, was more expressive (2.59%) than observed in 241 (0.21%) and CDC-E8392 (1.93%) strains. Electron microscopy of C. diphtheriae-infected HEp-2 cells revealed intracellular bacteria inside membrane-bound vacuoles. Bacterial internalisation was totally inhibited by 5 microM cytochalasin E and significantly inhibited by 100 microM genistein (P<0.05). Therefore, C. diphtheriae presents the ability to survive within cultured epithelial cells and signalling cascade as well as actin polymerisation are required for entry of diphtheria bacilli into HEp-2 cells.