Inhibition of Shiga toxin-converting bacteriophage development by novel antioxidant compounds

Abstract

Oxidative stress may be the major cause of induction of Shiga toxin-converting (Stx) prophages from chromosomes of Shiga toxin-producing Escherichia coli (STEC) in human intestine. Thus, we aimed to test a series of novel antioxidant compounds for their activities against prophage induction, thus, preventing pathogenicity of STEC. Forty-six compounds (derivatives of carbazole, indazole, triazole, quinolone, ninhydrine, and indenoindole) were tested. Fifteen of them gave promising results and were further characterized. Eleven compounds had acceptable profiles in cytotoxicity tests with human HEK-293 and HDFa cell lines. Three of them (selected for molecular studies) prevent the prophage induction at the level of expression of specific phage genes. In bacterial cells treated with hydrogen peroxide, expression of genes involved in the oxidative stress response was significantly less efficient in the presence of the tested compounds. Therefore, they apparently reduce the oxidative stress, which prevents induction of Stx prophage in E. coli.

Temperate Bacteriophages—The Powerful Indirect Modulators of Eukaryotic Cells and Immune Functions

“…This strategy has been called "bacterial altruism" and exemplifies another way in which the presence of the prophage may influence survival of the host, this time when considering the whole population of lysogenic bacteria rather than a single cell [46]. Bloch et al (2018) investigated 46 chemical compounds and their impact on E. coli prophages encoding Shiga toxin [47]. Three compounds (CM032D, CM092 and CM3186B) prevented the expression of prophage genes.…”

“…The addition of the three mentioned compounds caused inhibition of expression of oxidative stress genes in E. coli. Reducing the effect of the stress factor contributed to the prevention of the release of prophage-encoded Shiga toxin in E. coli and the prevention of bacterial pathogenicity [47].…”

Prophage Activation in the Intestine: Insights Into Functions and Possible Applications

“…Moreover, low-fidelity polymerase pol VICE391 (RumA’2B) encoded by conjugative transposone R391 could further promote higher levels of spontaneous SOS mutagenesis, partly because of the longer binding time of RumB to genomic DNA ( Walsh et al, 2019 ). While the mechanisms of some prophage inducers (for example, diet, clove, stevia, grapefruit seed extract, and aspartame)-mediated prophage activation have remained poorly understood, inflammation (e.g., reactive nitrogen species, reactive oxygen species, and hypochlorite), dietary fructose, nitric oxide, SCFAs, β-lactam antibiotics, and hydrogen peroxide have been shown to induce phage production by activating the SOS response in Salmonella enterica Typhimurium ( S .Tm) SL1344, L. reuteri 6475, EHEC O157, Lactococcus lactis NZ9000, Staphylococcus aureus , and Escherichia coli MG1655, respectively ( Maiques et al, 2006 ; Howe et al, 2016 ; Diard et al, 2017 ; Ichimura et al, 2017 ; Bloch et al, 2018 ; Kim and Bae, 2018 ; Oh et al, 2019 ; Boling et al, 2020 ).…”

“…In contrast, cinnamon oil eliminated RecA protein, polynucleotide phosphorylase, and poly(A) polymerase in Escherichia coli O157:H7, thereby inhibiting prophage activation and Shiga toxin production ( Figure 2B ; Sheng et al, 2016 ). Under oxidative stress conditions, suppressing induction of the prophage in Shiga toxin-producing Escherichia coli using some derivatives (for example, CM092, CM032D, and CM3186B) of quinolone, indazole, indenoindole, triazole, carbazole, and ninhydrine reduced bacterial virulence ( Bloch et al, 2018 ). This inhibitory effect on prophage induction was achieved by increasing the expression of genes responsible for encoding c I repressor and reducing the expression of oxidative stress genes as well as phage lysis genes.…”

The lysogenization of the non-O157 Escherichia coli strains by stx-converting bacteriophage phi24B is associated with the O antigen loss and reduced fitness

“…Toxin molecules lacking the signal peptide for secretion are released upon cell lysis. The lysogeny in stx-converting phages is less stable compared to stx-lambdoid phages [17][18][19][20] resulting in higher rate of spontaneous induction and in increased sensitivity to environmental factors such as DNA-damaging agents, oxidative stress or increased salt concentrations. Many antibiotics also increase the induction rate of Stxconverting prophages thus enhancing the toxin production.…”