Bacterial Food-borne illness-Intoxication & Toxicoinfection

• Clostridium botulinum


  Bacterial agent of foodborne illness by intoxication
• Botulism


  Rare but sometimes deadly disease
• Early evidence: botulism confined to meat products (1973)
• 13 people fell ill & 6 later died after eating a Blunzen (sausage made by packing blood & other ingredients into a pig's stomach, boiled & smoked: stable at room temp for several weeks)
• Later found to occur wherever foods & their processing offer conditions suitable for survival and growth
• According to ICMF, microbes grouped by risk of severity: Severe direct hazards, life-threatening, chronic sequelae, long duration, death

  
• Around 145 cases are reported each year in the USA (CDC): 15% food-borne, 65% infant botulism, 20% wound
• Sources of C. botulinum spores

  • Soil (cultivated and forest)
  • Dust
  • Plants
  • Bottom of sea sediments, aquatic mud
  • Animals (low # of GI tract of some birds, fish & mammals)
  • Carried by bees
• C. botulinum


  • Rod G (+): straight or slightly curved (2-10 m)
  • Spore-forming: central or subterminal oval spores
  • Obligate Anaerobe (VP)
  • Motile (by peritrichous flagella)

  
• Proteolytic strains


  Mesophilic (10-45C, Topt. 35C), more heat-resistant spores
• Non-proteolytic strains


  Psychrotrophic (3.3-45C, Topt. 30C), less heat-resistant spores
• Spore destroyed: sterilization (121C), Toxin destroyed: 80ºC for 10 min

  
• pH


  min pH 4.6, max pH 8.5-8.9
• Neurotoxins


  7 serologically distinct (A,B,C1,D,E,F,G), "the most toxic substances known"
• Humans: most susceptible to types A, B, E (most cases of botulism) & F
• C. botulinum Type A has a wide variety of uses in medicine, & cosmetic (BOTOX® cosmetic by Allergan ©)
• C. botulinum grouping


  • Proteolytic
  • Non-Proteolytic

  
• Proteolytic strains


  Food: partial disintegration & slight rancid or cheesy odour, more heat-resistant spores, problem for canning industry
• Non-proteolytic strains


  Psychrotrophic, potential hazard in chilled food, grow slowly & produce toxin at 3C, lesser acid tolerance

  
• Botulism is extremely rare but when it does occur it is often 20-50% fatal, depend on various factors: toxin type, amount ingested, type of food, speed of treatment

  
• Lethal dose: 10-8 g (0.00000001), the most powerful substance
• Botulism (adult)


  1. Ingestion of the neurotoxin botulin preformed in the food

  2. Toxins absorbed from intestine

  3. Spread to the peripheral nerves

  4. Block the transmission of impulse producing a flaccid paralysis, cardiac failure & respiratory failure

  
• Infant Botulism


  1. Ingestion of spores

  2. Spores geminate, grow & produce toxin in the gut

  
• Flaccid paralysis - C. botulinum


  Initial stage occurs between 8h to 8 days (average: 12-48h) after consumption of the toxin-containing food, GI disorders, Neurological Symptoms, Paralysis of different involuntary muscles that spreads to the lungs & heart, Death usually results from respiratory failure
• Surviving patients may take as long as 8 months to recover, dependent on early diagnosis & treatment
• 4 common features in botulism outbreaks

  • Food contaminated at the source or during processing with spores or vegetative cells
  • Food received some treatment that restricts the competitive microflora
  • Conditions in the food (temperature, pH, Eh, aw) were suitable for growth
  • Food is consumed cold or after a mild heat treatment insufficient to inactive toxin

  
• Foods associated with botulism outbreaks

  • Improperly canned foods
  • Garlic in oil
  • Vacuum-packed and tightly wrapped food (no Oxygen)
  • Canned low-acid (pH 4.6) foods, especially home canned
  • Improperly processed or damaged canned foods
• In US, botulism outbreaks occurred from 1973 to 1987 - 231 botulism outbreaks, 56 occurred at home, A large number of outbreak were associated with canned fruits & low-acid vegetables

  
• Botulism (type E C. botulinum) outbreak associated with dried salted fish in November-December 2016 in Germany and Spain; 6 cases reported

  
• Type E is found in the sea, ponds, rivers, so found in fish intestine and gills
• The 2nd highest incidence in finfish including fermented, improperly cooked, & smoked fish & fish eggs
• Common contaminant in fish products, which have been poorly eviscerated and/or self-salted at home. Contamination in commercial fish products has also been reported.
• C. botulinum


  Type E is found in the sea, ponds, rivers. Found in fish intestine and gills.

  
• The 2nd highest incidence of botulism outbreaks is in finfish including fermented, improperly cooked, & smoked fish & fish eggs.
• Fish & aquatic environment can be contaminated with C. botulinum, particularly type E.
• Uncooked fish products responsible for several botulism outbreaks.
• Smoked fish consumed without reheating - Hot-smoked fish: antimicrobial effect of heat, salt, smoke chemical, surface drying had been reduced in line with the perceived consumer preference for less strong flavored product.
• Early 1960's, two outbreaks in North America: type E associated with vacuum-packed, hot-smoked fish caused considerable alarm & led to Canada banning the importation of all types of packaged fish.

  
• HACCP in food plants

  1. Temperature control

  2. Appropriate techniques (time temperature control) when home canning low acid products

  3. Canned foods having pH 4.6 (low acid) and aw 0.86 must receive a "12D botulism cook" or 12 Log reduction (121ºC, 3 min or equivalent)
• Additional precautions, using hurdle technology

  1. Combination of various barriers e.g. nitrite/nitrate, NaCl, low pH, low aw, low temperature

  2. Min of 3% NaCl & an internal Temperature not less than 63ºC during smoking & the product should be storage below 4ºC