All bacteria 2

Gram ± V. parah

Negative

Shape V. parah

Comma

Infection/intoxication V. parah

Infection

Sporeformer? V. parah

No

D/R V. parah

10⁵

Temperature V. parah

5-45C

• But can grow at low temperatures (in fridge)

pH V. parah 

5-8

(An)aerobe? V. parah

facultative anaerobe

Can it handle drying? V. parah

No

Source V. parah

Sea water, raw fish, shell fish, water bodies with temperatures above 20C

Survival V. parah

• Can handle low temperatures

• Sensitive to drying

• Has barrier degrading enzymes

  • Lipolytic enzymes that act on lipids (milk) releases fatty acids and causing rancidity.

Contamination V. parah

• Off odors are created when above spoilage level, sugar becomes depleted and microbe switches to amino acids. 

Gram ± Bacillus cereus

Positive

Shape Bacillus cereus

Rod

Sporeforemer? Bacillus cereus

Yes

Infection or toxication? Bacillus cereus

Both

D/R Bacillus cereus

10⁵ or higher

Temperature Bacillus cereus

5-45C

However has:

• Psychrotolerant strains: 4-25°C  

• Mesophilic strains: 12-45°C 

pH Bacillus cereus

5-8

Aerobic/anaerobic Bacillus cereus

Facultative anaerobe

Dry survival? Bacillus cereus

Yes

Source Bacillus cereus

Rice prepared in bulk: slow cooling down ---> emetic type 

Products involved: vegetables, spices, sauces, dessert, dairy, meat products---> diarrohoeal type. 

Survival Bacillus cereus

Its spores are resistant structures. 

It has barrier degrading enzymes, proteolytic enzymes that act on protein (milk) leading to coagulation of protein, and release of nutrients. 

 

Prefers glucose > lactic acid > creatine 

Disease Bacillus cereus

Can cause foodborne illness through the production of toxins 

Toxins are produced in stationary phase of growth curve. 

 

Two types: 

1. Emetic type 

2. Diarhhoel type 

 

Emetic type Bacillus cereus

1. Emetic type

• Cause: Ingestion of a preformed toxin called cereulide, a heat- and acid-stable cyclic peptide.

• Source: Often associated with starchy foods like rice, pasta, or potatoes that have been cooked and then improperly stored at warm temperatures (allowing B. cereus to grow and produce toxin).

• Onset: Rapid — symptoms usually appear within 0.5 to 6 hours after eating the contaminated food.

• Symptoms:

  • Nausea

  • Vomiting (most prominent)

  • Sometimes mild abdominal cramps

• Incubation: 0.5-5 hours

• Duration: Generally self-limiting, lasting about 6–24 hours.

Diarrheal type Bacillus cereus

• Cause: Ingestion of B. cereus spores/vegetative cells → these survive stomach passage, germinate in the small intestine, and produce enterotoxins (such as Hbl, Nhe, CytK) inside the gut.

• Source: Associated with a wider range of foods — meat, milk, vegetables, sauces, soups, and desserts.

• Onset: Slower than emetic type, usually 8–16 hours after ingestion.

• Symptoms:

  • Watery diarrhoea

  • Abdominal cramps

  • Nausea (less common than in emetic type)

• Incubation: 6-24h

• Duration: Also self-limiting, lasting about 12–24 hours.

Gram ± Clostridium perfringens

Positive

Shape Clostridium perfringens

Rod

Spore former? Clostridium perfringens

Yes

Infection/intoxication? Clostridium perfringens

Infection

Toxico-infection: 

Toxin 5-20% of the strains produces toxin when vegetative cells sporulate in gut → enterotoxin 

Cl. perfringens can produce toxins in both the intestinal tract and food 

D/R Clostridium perfringens

10⁵ or bigger

Temperature Clostridium perfringens

5-45C

pH Clostridium perfringens

5-8

(an)aerobe Clostridium perfringens

Anaerobic

Can it handle drought? Clostridium perfringens

yes

Motile? Clostridium perfringens

No

Symptoms For type A and C (Clostridium perfringens)

A: Diarrhoea, nausea, bellyache (gas)

Type C: (rare) severe diarrhoea, enteritis

Incubation and duration of type A Clostridium perfringens

Incubation: 8-24h

Duration: 1-2 days

In what foods is Clostridium perfringens found?

• Poultry

• Spices

• Soup

• Sauces

• Vegetables

Prevention and control Clostridium perfringens

Proper chilling of food

Gram ± Clostridium botulinum

Positive

Shape Clostridium botulinum

Rod

Sporeformer? Clostridium botulinum

Yes

Intoxication/infection Clostridium botulinum

Intoxication

Optimal temperature? Clostridium botulinum

5-45?

optimal pH Clostridium botulinum

5-8

(An)aerobe? Clostridium botulinum

Anaerobe

Does it survive in dry conditions? Clostridium botulinum

Yes

Source Clostridium botulinum

Soil, vegetables, fish

Survival Clostridium botulinum

Its spores are highly resistant structures

Two groups of Clostridium botulinum

• Group 1: Proteolytic strains

  • Growth > 10 C

  • Heat resistant spores

  • Botulinum cook (12D) for low-acid foods stored at ambient temperature (3 min at 121 C)

• Group 2: Non-proteolytic strains

  • Growth > 3C

  • Spores inactivated at 90 C

Disease Clostridium botulinum

• Clostridium botulinum creates a toxin, with is lethal

• This toxin is activated in the gut of humans

• Symptoms: nausea, vomiting, muscular pain, double vision

• Infant botulism: The digestive system ingests bacterial spores, instead of only the toxin, which grows and produces toxin within the gut. 

Incubation & duration of botulism with Clostridium botulinum

• Incubation: 12-48 h

• Duration: 1-8 days

Prevention and control Clostridium botulinum

• A "Botulinum cook" is a specific heat treatment required for low-acid canned foods (pH > 4.5) to ensure a 12-log (12D) reduction in the level of Clostridium botulinum. 

• At pH<4.5 Clostridium botulinum does not grow anymore below this pH

• To achieve this 12D reduction (with D121 = 0.2 min), 2.4 minutes of heating at 121°C is needed, often referenced as an F0 or F121 value of 3 minutes. 

• It is important to note that a "Botulinum cook" does not achieve full sterilization, meaning other spoilage organisms may still survive 

• Nitrite above 100 mg/kg inhibits Clostridium botulinum, which might survive the heating process applied to many cured meats.   

Type A, B, C, D, E and F Clostridium botulinum

• Type A, B, E and F cause human botulism where toxin blocks end of nerves

• Type C and D are found on decaying carcasses

• and type A is also used for muscle paralysis. (Botox)

Gram ± E. coli

negative

Shape E. coli

Rod

Infection/intoxication E. coli

Infection

Dose response level E. colI

10

Temperature E. coli

5-45 (Mesophile)

pH E. coli

3-8

(An)aerobic? E. coli

facultative anaerobe

Aw E. coli

0.95, this level is needed for growth but can survive lower

Source E. coli

Cow faeces, raw beef, milk, vegetables contaminated with manure.

Family E. coli

Enterobacteriaceae

Which type of E. coli causes disease?

• E. coli O157:H7

Symptoms EIEC E. coli

Dysentery and fever

Symptoms EHEC E. coli

Bloody and diarrhoea and HUS

What is HUS

Haemolytic Uremic Syndrome, happens in children and is fatal. Infections mostly occur in less developed countries with insufficient hygiene. Or also countries consuming raw beef.

Symptoms EPEC E. coli

Watery stools and vomiting

Symptoms ETEC E. coli

Traveller’s diarhoea

Why are there more E. coli infections in the summer?

• More ground beef is eaten

• More difficult to keep the temperature below 7C

Prevention and Control E. coli

• For producers: It is essential to protect foods from contact with faeces (e.g., through manure management), manage risks associated with irrigation water, and maintain good general hygiene (cleaning, storage).

• For industry: Good slaughtering practices are needed to reduce carcass contamination, personnel require training, and food treatments such as cooking, pasteurization, and rapid fermentation should be applied.

• For consumers: Education on proper heating (e.g., of hamburgers and vegetables), preventing cross-contamination, maintaining the cold chain, and using safe water is crucial.

• Heat treatment is a primary prevention method