Effects of zinc supplementation on Shiga toxin 2e-producing <i>Escherichia coli in vitro</i>

Abstract

Swine edema disease is caused by Shiga toxin (Stx) 2e–producing Escherichia coli (STEC). Addition of highly concentrated zinc formulations to feed has been used to treat and prevent the disease, but the mechanism of the beneficial effect is unknown. The purpose of the present study was to investigate the effects of highly concentrated zinc formulations on bacterial growth, hemolysin production, and an Stx2e release by STEC in vitro. STEC strain MVH269 isolated from a piglet with edema disease was cultured with zinc oxide (ZnO) or with zinc carbonate (ZnCO3), each at up to 3,000 ppm. There was no effect of zinc addition on bacterial growth. Nonetheless, the cytotoxic activity of Stx2e released into the supernatant was significantly attenuated in the zinc-supplemented media compared to that in the control, with the 50% cytotoxic dose values of 163.2 ± 12.7, 211.6 ± 33.1 and 659.9 ± 84.2 after 24 hr of growth in the presence of ZnO, ZnCO3, or no supplemental zinc, respectively. The hemolytic zones around colonies grown on sheep blood agar supplemented with zinc were significantly smaller than those of colonies grown on control agar. Similarly, hemoglobin absorbance after exposure to the supernatants of STEC cultures incubated in sheep blood broth supplemented with zinc was significantly lower than that resulting from exposure to the control supernatant. These in vitro findings indicated that zinc formulations directly impair the factors associated with the virulence of STEC, suggesting a mechanism by which zinc supplementation prevents swine edema disease.

Antimicrobial impacts of zinc oxide nanoparticles on Shiga toxin-producing Escherichia coli (serotype O26)

“…Figure 6 showed that ZnO NPs -regulated the expression of the Stx2 gene, and there was a strong correlation between the down-regulation of the Stx2 gene and ZnO NPs concentrations. These results agree with previous studies that clarified that zinc exerts inhibitory effects on STEC strains and Stx expression (Crane et al, 2011;Crane et al, 2014;Uemura et al, 2017).…”

“…Thus, ZnO NPs suppressed Shiga toxin production. This result is supported by the finding of Uemura et al (2017), who reported a significant reduction in the cytotoxic activity of Stx2 in zinc-supplemented media compared to the control. Also, quantitative real-time PCR (qPCR) was performed to detect the Stx2 gene.…”

Probiotics, Galacto-oligosaccharides, and zinc antagonize biological effects of enterohaemorrhagic Escherichia coli on cultured cells and brine shrimp model

“…It is also known that, in growth conditions, Zn can specifically inhibit the expression of Shiga toxin by blocking the regulation of its production. In addition, Zn is more potent and efficient than other metals such as iron, manganese, and nickel in reducing the production of Shiga toxin (Crane et al, 2014;Uemura, Katsuge, Sasaki, & Goto, 2017). Taking into account that our experiments were done with EHEC supernatant (Figs.…”

Induction of antitoxic antibody and preventive effect against porcine edema disease by the pentameric Stx2eB subunit vaccine

“…In addition, as multidrug-resistant bacteria have been reported, antibiotics need to be selected appropriately [ 1 ]. As an alternative method, high amounts of zinc oxide may be added to feed [ 3 ], but there are concerns about the increase of drug-resistant bacteria and environmental pollution by zinc. Therefore, the exploitation of other control tools for ED, such as vaccines, is desired.…”