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The Significance of Salmonella to the Food Industry

By: , Posted on: August 28, 2015

salmonellaSources of Salmonella

Many biological entities, living and dead, act as reservoirs of Salmonella, and a diversity of foods have been implicated in outbreaks of foodborne disease ( Table 7). As the natural habitat of salmonellae significant with respect to foodborne disease is the gastrointestinal tract of humans and other primarily warm-blooded animals, it is not surprising that the major food vehicles of transmission are animal-derived foods. Plant foods also may act as vehicles, following environmental contamination.

Table 7

table salmonella

Both animal and, to a lesser extent, plant-derived animal feed materials are important in the persistence of salmonellae in the food production environment. This is exemplified in the poultry industry, where stringent control of feed materials results in a significant decline in the carriage rate of Salmonella by poultry.

In geographic regions where environmental sanitation is poor, water also represents a significant source of transmission, directly through consumption, but also, importantly with respect to the food industry, through use in food processing, particularly when water is used with minimally processed foods.


Worldwide, foodborne bacterial infection associated with Salmonella is considered to be second only to that involving Campylobacter, with the incidence of Salmonella infection seemingly increasing. To some extent, the increase may be attributed to better reporting and surveillance, rather than a real increase in disease. Nevertheless, a significant proportion of the reported cases represents an actual increase.

The case rate for human salmonellosis varies immensely, from <1 to >300 per 100 000 population and is profoundly influenced by geographic, demographic, socioeconomic, meteorological, and environmental factors.

Concerning specific serovars, the dominant type associated with foodborne illness for many years in many parts of the world was the ubiquitous Typhimurium. From the early 1980s, a major public health problem began to emerge, involving strains of serovar Enteritidis capable of systemic colonization of poultry leading to widespread foodborne disease associated with consumption of contaminated eggs and raw or lightly cooked foods containing them.

Since the early 1990s, a specific type of Salmonella Typhimurium known as definitive type (DT) 104 has become a major problem in the United Kingdom and Western Europe and now also in the United States. Strains of S. Typhimurium DT104 are extremely invasive, and many contain large plasmids, conferring resistance to a range of antibiotics, including ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline. Still newer strains have been found to be resistant to trimethoprim and ciprofloxacin.

Different regions of the world experience problems with specific serovars from time to time. Using Australia as an example, more than 80% of human infections with serovar Virchow occur in the state of Queensland, whereas those involving serovar Mississippi are largely confined to Tasmania.

Control of Salmonella

Control of Salmonella with particular regard to foodborne disease is problematic, given the close links between the environment, feeds, food animals, and humans and, broadly, requires vigilance at two levels, in food production and food processing.

A range of management strategies have been developed or devised to control salmonellae in food production environments, particularly that for the production of poultry, a major vehicle of transmission of Salmonella. These strategies include the provision of Salmonella-free stock and feed, stringent biocontrol, particularly of rodents, vaccination with attenuated Salmonella strains, and use of probiotic preparations (e.g., competitive exclusion).

Perhaps the most important control measure in food processing involves education, first of commercial food handlers in the areas of personal and food hygiene, particularly in the food service sector of the food industry, and second of consumers, who are the food handlers involved in food service at the domestic level.

Although Salmonella may never be eliminated completely, significant reduction should be achieved through the application of appropriate control strategies within a well-developed and implemented hazard analysis and critical control point–based food safety plan from the commencement of production through to consumption.

Food Science Reference Module coverThis excerpt was taken from the introductory article to Salmonella from the Second Edition of the Encyclopedia of Food Microbiology. We are excited to announce that the Reference Module in Food Science will be live on ScienceDirect December 2015 and will include this article along with thousands of articles from our food reference works and articles exclusive to the Reference Module. The Reference Module will be continuously reviewed, updated and added to ensuring you are kept up to date with the latest developments in the field.

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