|Nisbet, David - Dave|
Submitted to: Journal of Rapid Methods and Automation in Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/7/2004
Publication Date: 12/20/2004
Citation: Park, S.Y., Woodward, C.L., Birkhold, S.G., Kubena, L.F., Nisbet, D.J., Ricke, S.C. 2004. Influence of oxidation-reduction reductants on Salmonella typhimurium growth rates after initial pH adjustment and zinc compound addition. Journal of Rapid Methods and Automation in Microbiology. 12:185-197. Interpretive Summary: Alternative compounds, such as organic acids, act adversely on some bacteria that cause disease and may be considered for use instead of antibiotics. This is especially true since there are considerable public concerns about the development of antibiotic resistance that makes treatment of clinical disease in humans more difficult. Salmonella, a particular group of bacteria that cause human illness, grow best under conditions that are not acidic or basic but close to neutral. Controlling these conditions may be one of the best ways to stop or slow down growth of Salmonella during food processing and preservation. As food processing involves more use of packaging materials that limit oxygen transfer and change the atmosphere surrounding the food, there is a need to understand how these changes influence the effectiveness of antimicrobial compounds. In the present research, we studied the relationship between acidic conditions, the addition of products that change the chemical nature of other compounds, and zinc compounds (zinc acetate and zinc sulfate) on the growth of Salmonella typhimurium in growth media without using animals. The results of this study suggest that a combination of zinc compounds and acidic conditions may reduce the growth of foodborne Salmonella under conditions of no oxygen. This is important because the food processing industry may use this information to produce products with less contamination by foodborne bacteria, thus lessening the risk of human illness.
Technical Abstract: The objective of this study was to examine the interaction between acidic pH, addition of reductants and zinc (Zn) compounds (Zn acetate and Zn sulfate) on the anaerobic growth of a Salmonella typhimurium poultry isolate in rich or minimal media. The anaerobic growth of S. typhimurium in TSB medium was significantly inhibited by either acidic pH levels (pH 4: 0.18, pH 5: 0.20, pH 6: 0.40, pH 7: 0.57 h**-1) or higher concentrations of Zn acetate (0.67%: 0.43, 3.35%: 0.33, and 6.03%: 0.26 h**-1). S. typhimurium anaerobic growth in M9 minimal medium was significantly inhibited by either acidic pH level or higher concentrations of Zn acetate or Zn sulfate. Most anaerobic growth rates of the S. typhimurium poultry isolate in acidic and higher concentrations of Zn acetate or Zn sulfate were less than 0.10 h**-1. The overall anaerobic growth rates of S. typhiurium were more inhibited in the presence (0.089 h**-1) of reductants than in the absence (0.102 h**-1) of reductants in M9 medium. The results in this study suggest that a potential combination of Zn compounds and acidic pH could reduce growth of foodborne Salmonella under anaerobic conditions.