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Inoculation onto solid surfaces protects Salmonella spp. during acid challenge: a model study using polyethersulfone
Purushottam V Gawande1, Arvind A Bhagwat
1Produce Quality and Safety Laboratory, Henry A. Wallace Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, Maryland 20705-2350, USA.
Applied and Environmental Microbiology
|January 5, 2002
Summary
Fresh-cut produce and other surfaces increase Salmonella acid tolerance, enhancing survival during stomach acid challenges. This surface-associated protection requires new protein synthesis.
Area of Science:
- Food safety
- Microbiology
- Gastroenterology
Background:
- Salmonellae are a leading cause of foodborne gastroenteritis outbreaks in the US.
- The oral infective dose (ID) varies significantly, from millions of cells in trials to as few as 100 cells with solid foods.
Purpose of the Study:
- To investigate how fresh-cut produce surfaces affect Salmonella acid tolerance.
- To understand the mechanisms behind increased pathogen survival on solid surfaces.
Main Methods:
- Inoculating Salmonella onto fresh-cut produce, inert membranes, and tissue paper.
- Challenging inoculated surfaces with acidic conditions (pH 3.0) and measuring survival rates.
- Utilizing polyethersulfone membranes as a model system for surface-associated protection studies.
Main Results:
- Fresh-cut produce surfaces enhance Salmonella's acid tolerance, increasing survival by 4-5 log units during acid challenge.
- Surface association, not produce acidity, confers resistance to stomach acidity.
- This acid protection mechanism requires de novo protein synthesis and is independent of stationary-phase sigma transcription factors.
Conclusions:
- Solid surfaces, including fresh-cut produce, play a critical role in increasing Salmonella's resistance to acid.
- Understanding surface-associated acid protection is crucial for mitigating foodborne illness risks associated with Salmonella.
- The findings provide insights into pathogen survival strategies on food matrices.