Abstract
Corynebacterium diphtheriae, the aetiologic agent of diphtheria, also represents a global medical challenge because of the existence of invasive strains as causative agents of systemic infections. Although tellurite (TeO32-) is toxic to most microorganisms, TeO32--resistant bacteria, including C. diphtheriae, exist in nature. The presence of TeO32--resistance (TeR) determinants in pathogenic bacteria might provide selective advantages in the natural environment. In the present study, we investigated the role of the putative TeR determinant (CDCE8392_813gene) in the virulence attributes of diphtheria bacilli. The disruption of CDCE8392_0813 gene expression in the LDCIC-L1 mutant increased susceptibility to TeO32- and reactive oxygen species (hydrogen peroxide), but not to other antimicrobial agents. The LDCIC-L1 mutant also showed a decrease in both the lethality of Caenorhabditis elegans and the survival inside of human epithelial cells compared to wild-type strain. Conversely, the haemagglutinating activity and adherence to and formation of biofilms on different abiotic surfaces were not regulated through the CDCE8392_0813 gene. In conclusion, the CDCE8392_813 gene contributes to the TeR and pathogenic potential of C. diphtheriae.
Highlights
Tellurium (Te) is a metalloid that exists as a trace component in natural environments
Little is known about the mechanisms of TeO32--resistance (TeR), numerous plasmid and/or chromosomally encoded TeR determinants have been identified in different bacterial species, including human pathogens
Online | memorias.ioc.fiocruz.br a: toxicity evaluated by polymerase chain reaction for tox gene (Pimenta et al 2008); b: p < 0.05 according to unpaired t test; Bacterial adherence to n-hexadecane (BATH): bacterial adherence to n-hexadecane; CDC: Centres for Disease Control and Prevention; DA: diffuse adherence [characterised by bacteria randomly distributed over the surfaces of the human epithelial type 2 (HEp-2) cells]; K2TeO3: potassium tellurite; MIC: minimal inhibitory concentration; -: negative; +: positive; ++: moderately adherent to glass or polystyrene
Summary
Tellurium (Te) is a metalloid that exists as a trace component in natural environments. Previous studies have demonstrated that these determinants are involved in resistance to bacteriophages and colicins (Whelan et al 1995), antiseptics and disinfectants (Teitzel & Parsek 2003) and antimicrobials (Collins et al 2010, Pei et al 2013, Franks et al 2014) These genes have been implicated in adherence to epithelial cells (Yin et al 2009, Pei et al 2013) and susceptibility to reactive oxygen species (ROS) (Franks et al 2014). Online | memorias.ioc.fiocruz.br a: toxicity evaluated by polymerase chain reaction for tox gene (Pimenta et al 2008); b: p < 0.05 according to unpaired t test; BATH: bacterial adherence to n-hexadecane; CDC: Centres for Disease Control and Prevention; DA: diffuse adherence [characterised by bacteria randomly distributed over the surfaces of the human epithelial type 2 (HEp-2) cells]; K2TeO3: potassium tellurite; MIC: minimal inhibitory concentration; -: negative; +: positive; ++: moderately adherent to glass or polystyrene
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