Colonization of human epithelial cell lines by Corynebacterium ulcerans from human and animal sources

Abstract

Corynebacterium ulcerans is an emerging pathogen transmitted by a zoonotic pathway to humans. Despite rising numbers of infections and potentially fatal outcomes, data on the colonization of the human host are lacking up to now. In this study, adhesion of two C. ulcerans isolates to human epithelial cells, invasion of host cells and the function of two putative virulence factors with respect to these processes were investigated. C. ulcerans strains BR-AD22 and 809 were able to adhere to Detroit562 and HeLa cells, and invade these epithelial cell lines with a rate comparable to other pathogens as shown by scanning electron microscopy, fluorescence microscopy and replication assays. Infection led to detrimental effects on the cells as deduced from measurements of transepithelial resistance. Mutant strains of putative virulence factors phospholipase D and DIP0733 homologue CULC22_00609 generated in this study showed no influence on colonization under the experimental conditions tested. The data presented here indicate a high infectious potential of this emerging pathogen.

The killing of macrophages byCorynebacterium ulcerans

“…The more aggressive behavior of C. ulcerans 809 toward epithelial cells might be due to the additional Shiga-like toxin this strain carries. 27 Taken together, the observations made in this study hint to the existence of more than one active mechanism of C. ulcerans to cope with macrophage function. In line with this idea, initial sequencing of strains 809 and BR-AD22 25 as well as next generation sequencing of 9 C. ulcerans isolates 8 revealed a number of different virulence factors, which might influence survival of this pathogen besides the Shiga-like toxin of strain 809 as well as PLD and DIP0733 homolog CULC22_00609 of BR-AD22.…”

“…34 BR-AD22 strains carrying a pld and CULC22_00609 gene disruption, respectively, were generated and designated ELHA1 and ELHA3. 27,35 When cells were infected with these mutant strains and LDH release was measured, at MOI 1 strain ELHA1 showed 51 § 16 % and ELHA3 34 § 13 % cytotoxicity compared to the wild type, indicating a multifactorial mechanism of macrophage damage, which has to be analyzed in more detail in future. A complex interaction is also indicated by the fact that the defect of mutant strains observed at MOI 1 could be overcome by higher MOIs (data not shown).…”

“…Up to now, data on adhesion and invasion of epithelial cells, fibrinogen, fibronectin and collagen binding, antimicrobial profiles and arthritogenic potential of isolates were published. [26][27][28] In the study presented here, C. ulcerans 809 and BR-AD22 were characterized for the first time to our knowledge in respect to their interaction with macrophages as important part of the innate immune system in order to get deeper insight into the pathogenicity of this emerging pathogen. The interaction with macrophages was of special interest, since the closely related animal pathogen Corynebacterium pseudotuberculosis, a facultative intracellular bacterium, is able to survive and grow in macrophages in order to disseminate within the host, 3,29 and also the human pathogen C. diphtheriae is able to survive within human macrophages.…”

The C-terminal coiled-coil domain of Corynebacterium diphtheriae DIP0733 is crucial for interaction with epithelial cells and pathogenicity in invertebrate animal model systems

“…On the other hand, a recent study showed that a corresponding mutant for the DIP0733 homolog in C. ulcerans (CULC22_00609) showed no effect on adhesion to and invasion into epithelial cells [35]. Remarkably, this data corroborates with our study, as the coiled-coil domain of DIP0733 was predicted to be present only in C. diphtheriae and C. pseudotuberculosis and absent in C. ulcerans.…”

“…Whilst a dramatic break-down of transepithelial resistance was not observed for most of the C. diphtheriae strains tested by Ott and co-workers, C. diphtheriae DSM43989 showed the most severe effect after 3 h of infection [17], which was similarly demonstrated by the CDC-E8392 wild-type strain in this study. Conversely, other strain specific proteins and cellular niche factors may be involved in this process as similar effects were described for C. ulcerans 809 [35]. …”