Foodborne Illness occurs when a pathogen is ingested with food and establishes itself in a human host or when a toxigenic pathogen establishes itself in a food product and produces a toxic product that is ingested by a human host. Thus, foodborne illness is generally classified into two main categories, foodborne infection and foodborne intoxication.
Foodborne infections occur as a consequence of the growth of pathogens in the human body. Because an incubation period is usually involved, the time from ingestion until symptoms occur is much longer than that of foodborne intoxications. The two basic categories of foodborne infections are:
Invasive infections caused by pathogens that invade bodily tissues and organs. Included in this group are the viruses, parasitic protozoa, other parasites and invasive bacteria (e.g., Salmonella, Aeromonas, Campylobacter, Shigella, Vibrio parahaemolyticus, Yersinia and enteric-type Escherichia coli).
Toxicoinfections caused by infective bacteria that are not considered invasive in nature, but are capable of multiplication or colonization in the human intestinal tract and produce toxins. Included in this group are: Vibrio cholerae, Bacillus cereus (diarrheal-type), Clostridium botulinum (in infants), C. perfringens, and verotoxigenic E. coli (E. coli O157:H7 and others).
Foodborne intoxications are caused by ingestion of toxins produced by organisms that have grown to sufficient numbers in the ingested food product. In general, intoxication appears more rapidly after consumption of contaminated food than do infections. The primary bacteria-causing foodborne intoxications include: Clostridium botulinum, B. cereus (emetic-type), and Staphylococcus aureus.
There are other nonbacterial toxins that cause illness. Several foodborne toxins have been linked to shellfish; these include Paralytic Shellfish Poisoning (PSP), Diarrheic Shellfish Poisoning (DSP), Neurotoxic Shellfish Poisoning (NSP), and Amnesic Shellfish Poisoning. These toxins, typically associated with shellfish, cause foodborne illness through the consumption of mussels, clams, and scallops that have ingested toxic dinoflagellates (the toxin-producing organisms).
Ciguatera toxins are associated with certain tropical fish. Scombroid toxins result from the production of histamine caused by bacterial spoilage of fish.
Fungal toxins or mycotoxins can be of long-term carcinogenic concern with consumption of mold-contaminated foods (e.g., aflatoxins in contaminated corn, peanuts, or other foods and patulin from contaminated apple or other fruit products).