Non-Bacterial Agents of Food-Borne Illness

• MICR3265


  Course code for Microbiology of Food
• Lectures 17 & 18: Non-bacterial agents of food-borne illness - Mycotoxins, Biotoxins & Viruses
• Presented by Dr. Kelly Brathwaite
• Mycotoxins


  Secondary metabolites naturally produced by certain filamentous fungi (Moulds)
• Mycotoxins


  • May contaminate a variety of different crops (e.g., cereal, nuts, spices, fruits) in the field (before harvest) and during the storage of grains, dried fruits for example (post-harvest)
  • ≈ 25% of global food crops are contaminated with fungal toxins every year
  • A mouldy food is probably infected by several species of moulds & contaminated by several different mycotoxins
  • Contamination of food & feed grains is a serious economic problem for grain producers and processors and food safety problem due to their impact on human and animal health
• Fungi growth conditions


  Warm and humid conditions (T & aw)
• Mycotoxins


  • More than 400 identified mycotoxins are produced by some 200 varieties of fungi such as Fusarium, Aspergillus and Penicillium (≈ 27 toxins)

  
• Most studies focus on aflatoxins, ochratoxin A and the Fusarium toxins fumonisin, zearalenone & deoxynivalenol/nivalenol due to food safety and economic losses

  
• Ochratoxin A (OTA)


  Produced by Aspergillus ochraceus in tropical regions and Penicillium verrucosum in cold regions (Western Europe, Canada & certain areas of South America)
• Penicillium islandicum


  Produces 2 hepatotoxins (injurious to the liver) causing yellow rice disease: cyclochlorotine and carcinogenic luteoskyrin
• Mycotoxin toxicity


  • Mutagenic: causing DNA damage
  • Carcinogenic
  • Teratogenic: causing malformation of an embryo/fetus (aflatoxins, ochratoxin A & zearalenone)
  • Nephrotoxic: damaging of the kidney
  • Hepatotoxicity: damaging of the liver
  • Cytotoxic: damaging of the cells
  • Immunotoxic: damaging of the immune system by destroying immune cells
• Acute intoxication


  Exposure to high-dose mycotoxin; symptoms develop rapidly such as abdominal pain & diarrhoea
• Chronic intoxication


  Exposure to low-level mycotoxins for long period causing impairments in the liver, kidney, and immune system that can result in liver of kidney cancer
• Mycotoxin intake by feed or food causes chronic intoxication rather than acute symptoms
• Mycotoxins


  • Aflatoxins B1, B2, G1, G2
  • Ochratoxin A (OTA)
  • Patulin
  • Trichothecenes: T2, Deoxynivalenol (DON)
  • Zearalenone

  
• Aflatoxins


  • Produced by Aspergillus flavus & A. parasiticus
  • The 1st mycotoxins to be identified, recognized in 1960
  • Over 100,000 turkey died in UK by feeding on peanut meal contaminated with Aspergillus flavus producing aflatoxin
  • In 2006 - Several outbreaks of aspergillosis in Cumuto and Valencia farms in Trinidad: more than 6,000 chickens

  
• Types of aflatoxins


  • B1, B2, G1, G2, M1, M2
• Aflatoxin toxicity


  • Hepatotoxic (liver damage), chronic hepatitis (jaundice & cirrhosis), liver cancer, immunotoxic, teratogenic
  • B1 more toxic than (>) G1 > B2 > G2
• Heat processing, such as ultrahigh-temperature (UHT) treatment, pasteurization, roasting, and baking, and also cold storage do not affect aflatoxin in foods since they are fairly stable
• Ochratoxin A (OTA)


  • Potentially nephrotoxic (damaging of the kidney), carcinogenic, hepatotoxic, immunotoxic & teratogenic
  • Produced by Aspergillus ochraceus in tropical regions and Penicillium verrucosum in cold regions (Western Europe, Canada & certain areas of South America)
  • Kidney necrosis (especially in pigs)
  • Toxin accumulates into fat animals (poultry, pigs, cow) eating contaminated feeds & can be ingested by humans eating these meats
  • Mainly associated with cereals (barley, wheat crops)
• Foods where ochratoxin A may be found

  • Bread made with contaminated cereal
  • Dried beans, soybeans, coffee beans, cacao, moldy tobacco, country cured hams, nuts & peanuts, grape juice, red wine, beer, spices & dried fruits
• Patulin


  • Produced by several spp. of Penicillium & Aspergillus
  • Toxin production at min aw 0.81, also in lower temperatures (0–24°C)
  • In 1942: potentially useful antibiotic w. wide spectrum of activity
  • In 1959, recognized as mycotoxin after an outbreak of poisoning of cattle, being fed on germinated barley malt sprouts
  • Symptoms: acute (lung & brain edema, liver & kidney damage, and toxicity to the immune system), chronic (neurotoxic, teratogenic, immunotoxic, skin lesion & cancer)
  • Some outbreaks are associated with badly stored materials such as apples infected with P. expansum (chapter 5: blue mold, soft rot)
  • Fresh apple juice: limit of 50g/l
  • The presence of patulin in fruit juice is a useful indicator of very poor quality of fruits used in its manufacture
  • Stable at relatively low pH, but destroyed during the fermentation of apple juice to cider
• Deoxynivalenol (DON)


  • DON in carcinogenesis Group 3 of Trichothecenes toxins
  • Known as vomitoxin, is the most commonly detected in grains such as wheat, barley, oats, rye, and corn and less often in rice, sorghum
  • DON appeared in 81% of livestock feed from 81 countries worldwide
  • DON and Nivalenol inhibit cell metabolism (e.g., protein, DNA, and RNA synthesis), affect cell division and mitochondrial functions
  • DON is less toxic than Nivalenol
  • DON also shows teratogenic, neurotoxigenic, and immunosuppressant effects
  • Major symptoms such as abdominal discomfort, diarrhea, vomiting, and inflammation of the throat, weight loss, and anorexia
• Mycotoxin control/prevention


  • Good Farm Management Practice (GFMP)
  • Preventing plants from become infected with moulds
  • Adequate drying & storage of foods and feeds
  • Biological control e.g. infecting plant in the early stage with nontoxigenic strains of A. flavus to prevent the colonization of toxigenic strains in peanuts plants
  • Good manufacture practices (GMP)
  • Remove rotten & damaged fruits to be used for juice production
  • UV light used to screening for aflatoxins (fluorescence) in corn, cottonseed & figs, but not in peanuts since they autofluoresce: Peanuts containing aflatoxins are removed by electronic colour-sorting machines, which detect discoloured kernels
• Mycotoxin control/prevention (chemical treatments)

  • Ozone, H2O2 , & Anhydrous ammonia gas (↑T,P) used in peanut meals (95-98% reduction), more effective when applied together with heat
• Mycotoxin regulations


  • FDA: Aflatoxin M1 in milk: 0.5 ppb
  • Aflatoxins in human food: 20 ppb, 30 ppb (FAO/WHO)
  • Patulin in apple juice: 50 ppb
  • DON: 1 ppm in finished wheat products that may be consumed by humans
  • Barbados guidelines for mycotoxins

  
• Scombroid (Scombrotoxin or Histamine) food poisoning


  Caused indirectly by bacteria
• Histidine


  A naturally occurring amino acid that is present in higher proportions in the muscle of certain fish species, particularly those of the Scombridae family
• Scombroid food poisoning is primarily associated with consumption of fish flesh in species rich in free histidine
• Histidine decarboxylase


  • Certain bacteria produce the enzyme histidine decarboxylase during growth, which breaks down free histidine present in the fish (post-mortem) → histamine
  • Enzyme can remain active even after cooking

  
• Commodity


  • Mycotoxin(s)
  • Limit (µg/kg)
• Commodity


  • aflatoxins B1,B2,G1,G2
  • 20
• Commodity


  • aflatoxin M1
  • 0.5
• Commodity


  • aflatoxins B1,B2,G1,G2
  • 50
• Non-bacterial agents of foodborne illness

  Scombroid (Scombrotoxin or Histamine) food poisoning (caused indirectly by bacteria)
• Number of histamine poisoning outbreaks reported in the European Union during the years 2010-2018 [27-35]
• Fish species with high histidine

  • Scombrid (mackerels, tunas, and bonitos)
  • Clupeid (herrings)
  • Carangid (jacks)

  
• Histidine decarboxylase


  Certain bacteria produce the enzyme that breaks down free histidine present in the fish (post-mortem) → histamine

  
• The enzyme can remain active even after the bacteria responsible for producing it have been inactivated or killed
• The enzyme continues histamine production slowly at refrigeration temperatures and remains stable if frozen, thus allowing it to rapidly recommence activity after thawing