Growth Inhibition of Enteric Pathogens by Zinc Sulfate: An in vitro Study

Abstract

Objective: To determine the inhibition effect of zinc sulfate on isolates of enteric bacteria. Materials and Methods: Mueller-Hinton agar containing different concentrations of zinc sulfate was prepared. Isolates used in this study were obtained from local clinics. They were Salmonella typhi, Salmonella groups A, B, C, D and E, Escherichia coli, Enterobacter, Shigella and Vibrio cholerae. Overnight cultures of test organisms in brain-heart infusion broth were adjusted to 0.5 McFarland standard turbidity by adding normal saline with 1 µl of each adjusted broth culture inoculated onto zinc sulfate agar plates. The plates were incubated for 18–20 h at 37°C. The inhibition concentration was recorded as the lowest concentration of zinc sulfate that completely inhibited growth. Results: All enteric pathogens tested were inhibited by zinc sulfate. Of the isolates, S. typhi was most sensitive since 20% of the strains were inhibited by zinc sulfate of 0.8 mg/ml. Salmonella paratyphi A was inhibited at 1.2 mg/ml. Other Salmonella spp. were inhibited at concentrations between 1.4 and 2.0 mg/ml. V. cholerae O1 and Shigella flexneri demonstrated a similar pattern of inhibition as S. paratyphi A. A higher concentration of zinc sulfate (1.6 mg/ml) was required to completely inhibit Shigella sonnei. Conclusion: The findings indicate that zinc sulfate has an antimicrobial effect on enteric pathogens and may contribute to the treatment of diarrhea.

Zinc deficiency alters host response and pathogen virulence in a mouse model of enteroaggregativeescherichia coli-induced diarrhea

“…45 Zinc has been shown to inhibit the growth of other enteric pathogens such as salmonellae, Shigella, and Vibrio in vitro. 46 Additionally, we have previously shown an inhibitory effect of zinc on EAEC in vitro. 21 In the current study, we were able to demonstrate in vivo, increased expression of several aggR-regulated EAEC virulence factors in the absence of dietary zinc.…”

No Protective Effects of High-Dosage Dietary Zinc Oxide on Weaned Pigs Infected with Salmonella enterica Serovar Typhimurium DT104

“…Obviously, environmental and sanitary conditions, which differ between experiments, affect the effects of dietary supplements (28), and this may also be true for the effects of ZnO. Evidence for the antimicrobial activity of zinc in vitro (29) and for modification of the intestinal microbiome by high levels of dietary ZnO (13,14,30) has been reported. For example, a diet containing 2,500 mg Zn/kg caused a 0.5-to 2-log reduction in the number of intestinal Campylobacter species in weaned piglets (31).…”

Influence of Zinc Supplementation in Acute Diarrhea Differs by the Isolated Organism

“…Second and consistent with this observation, Canani et al [7] observed that zinc-induced promotion of ion absorption across the gut is evident in response to the ion secretion caused by Vibrio cholerae toxin but not the Escherichia coli heat-stable enterotoxin. Third, Surjawidjaja et al [8] showed that although zinc sulphate can inhibit the growth of enteropathogens in vitro, the lethal dose required to kill 50% of the organisms (LD 50 ) widely varies across the species of the causative organisms. Consequently it is possible that the overall beneficial effect of zinc supplementation observed in a trial may depend on the spectrum of the causative organisms within that study.…”