Topic 1 Food microorganisms, foodborne outbreaks and people at risk

Foodborne diseases are caused by contamination of food and occur at any stage of the food chain, from production to consumption. They can result from several forms of environmental contamination including pollution in water, soil or air, as well as unsafe food storage and processing.

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According to the Health Protection Surveillance Centre (n.d.), an outbreak of infection or foodborne illness may be defined as two or more linked cases of the same illness or the situation where the observed number of cases exceeds the expected number, or a single case of disease caused by a significant pathogen (e.g. diphtheria or viral haemorrhagic fever). Outbreaks may be confined to some of the members of one family or may be more widespread and involve cases either locally, nationally or internationally.

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According to the research of Lorenzo et al. (2018), the main groups of microorganisms of relevance for food safety and stability are:

  • spoilage non spore-forming bacteria. Microbial spoilage occurs either because of microbial growth in a food or because of the action of some microbial enzymes present in the food.
  • spoilage spore-forming bacteria. This type of bacteria is considered a major threat in heat-treated foods.
  • pathogenic non spore-forming bacteria. Although sporogenesis is considered an important environmental survival and food contamination mechanism in bacteria, several pathogenic bacteria that do not form spores remain involved in the main food contamination outbreaks in the last decade.
  • pathogenic spore-forming bacteria. This class of microorganisms is very important, due to their inherent ability to survive extreme processing conditions.
  • yeasts and moulds. The use of microorganisms to obtain different types of food, such as beer, wine, bread, cheeses, and fermented milk is very old.
  • viruses. Viruses are obligate intracellular parasites that cause a wide range of diseases in plants, animals, and humans. Consequently, virus multiplication will not occur in foods that can act only as a passive vehicle in the transmission of infection.

Certain conditions are needed for the development of microorganisms in foods. The ideal temperature for the growth of microorganisms is between 5°C and 63°C (The Food Safety Authority of Ireland, 2018). The moisture content of food is important for the development and reproduction of microorganisms. It has long been known that dried foodstuffs keep longer and are not able to support the growth of microorganisms. Under favourable conditions, microorganisms can double in size within 20 minutes (, 2020).