Abstract
BackgroundCorynebacterium diphtheriae, the causative agent of diphtheria, is well-investigated in respect to toxin production, while little is known about C. diphtheriae factors crucial for colonization of the host. In this study, we investigated strain-specific differences in adhesion, invasion and intracellular survival and analyzed formation of pili in different isolates.ResultsAdhesion of different C. diphtheriae strains to epithelial cells and invasion of these cells are not strictly coupled processes. Using ultrastructure analyses by atomic force microscopy, significant differences in macromolecular surface structures were found between the investigated C. diphtheriae strains in respect to number and length of pili. Interestingly, adhesion and pili formation are not coupled processes and also no correlation between invasion and pili formation was found. Using RNA hybridization and Western blotting experiments, strain-specific pili expression patterns were observed. None of the studied C. diphtheriae strains had a dramatic detrimental effect on host cell viability as indicated by measurements of transepithelial resistance of Detroit 562 cell monolayers and fluorescence microscopy, leading to the assumption that C. diphtheriae strains might use epithelial cells as an environmental niche supplying protection against antibodies and macrophages.ConclusionsThe results obtained suggest that it is necessary to investigate various isolates on a molecular level to understand and to predict the colonization process of different C. diphtheriae strains.
Highlights
Corynebacterium diphtheriae, the causative agent of diphtheria, is well-investigated in respect to toxin production, while little is known about C. diphtheriae factors crucial for colonization of the host
Cells were incubated for 1.5 h with bacteria, gentamicin was added to kill remaining extracellular C. diphtheriae and survival of intracellular bacteria was analyzed after different times of incubation (Fig. 2)
When invasion into D562 cells was analyzed for the six non-toxigenic strains and the toxigenic C. diphtheriae strain after 2 h, tox+ strain DSM43989 showed the lowest internalization rate with 0.014 ± 0.007%
Summary
Corynebacterium diphtheriae, the causative agent of diphtheria, is well-investigated in respect to toxin production, while little is known about C. diphtheriae factors crucial for colonization of the host. Corynebacterium diphtheriae is the causative agent of diphtheria, a toxaemic localized infection of the respiratory tract While this disease is well-controlled by vaccination against the diphtheria toxin in e. Non-toxigenic strains have been increasingly documented [4,5,6] and found to be the cause of invasive diseases such as endocarditis, bacteraemia, pneumonia, osteomyelitis, spleen abscesses, and septic arthritis [7,8]. As indicated by these systemic infections, C. diphtheriae is able to attach to host epithelial cells of larynx and pharynx, but must be
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