Bacillus and clostridium

Bacillus and Clostridium Overview

• Focus on two genera: Bacillus and Clostridium

• Both have significant implications for food safety and health.

1. Bacillus Genus

• Characterized by:

  • Aerobic to facultatively anaerobic conditions.

  • Rod-shaped bacteria.

  • Majority are catalase positive.

1.1. Key Species

Bacillus cereus

• Motility: Motile, facultative anaerobe.

• Optimal Temperature: 30°C, can grow between 5°C and 50°C.

• Distribution: Ubiquitous in nature.

• Biofilm Formation: Capable of producing biofilms.

• Enzymatic Activity:

  • Produces enzymes leading to food spoilage:

    • Rennet-like enzyme: Causes sweet curdling in milk.

    • Lecithinase and protease: Leads to bitter cream.

1.2. Food Poisoning Cases from Bacillus cereus

Emetic Syndrome

• Due to heat-stable toxin.

• Incubation Time: 0.5 to 6 hours.

• Symptoms:

  • Nausea,

  • Vomiting,

  • Abdominal cramps.

• Foods Associated: Rice products and starchy foods.

Diarrheal Syndrome

• Caused by heat-labile toxin.

• Incubation Time: 6 to 16 hours.

• Symptoms:

  • Abdominal cramps,

  • Diarrhea.

• Foods Associated: Milk, meats, fish, and vegetables.

1.3. Toxicological Characteristics

• Infective Dose:

  • Emetic: 10^5 - 10^8 cells/g.

  • Diarrheal: 10^5 - 10^7 cells/g.

• Toxin Production:

  • Emetic: Cyclic peptide (cereulide).

  • Diarrheal: Three protein sub-units.

• Symptoms Duration:

  • Emetic: 6-24 hours.

  • Diarrheal: 12-24 hours.

• Foods Most Implicated:

  • Emetic: Fried/cooked rice, pasta.

  • Diarrheal: Meat products, soups, dairy.

2. Other Bacillus Species

2.1. Bacillus subtilis

• Characteristics:

  • Non-pathogenic,

  • Strict aerobe.

• Spoilage:

  • Causes sweet curdling and bitty cream in milk,

  • Ropiness in baked products.

2.2. Bacillus licheniformis

• Growth Conditions: Facultative anaerobe.

• Spoilage Aspects: Ropiness in bread.

• Salinity Tolerance: Can grow at 7% NaCl.

2.3. Bacillus coagulans

• Characteristics:

  • Facultative anaerobe,

  • Aciduric (pH 4).

• Impact: Causes flat-sour spoilage in canned foods.

2.4. Geobacillus stearothermophilus

• Facultative anaerobe

• Non-pathogenic

• Obligate thermophile (45-65C)

• pH 5 requirement for initial growth

• Flat sour spoilage of canned good

3. Clostridium Genus

• Characteristics:

  • Anaerobic, unable to form a respiratory chain,

  • Catalase negative.

  • Indigenous soil or water organisms.

3.1. Clostridium perfringens

• Growth Conditions:

  • Optimal temperature range: 37-45°C (20-50°C possible).

  • Inhibited at pH ≤ 5.

• Metabolism: Uses sugars to produce butyric acid, hydrogen, and carbon dioxide.

• Common Vehicles for Spoilage: Meat and poultry, seafood.

• Toxicity:

  • Cannot synthesize 13 out of 20 amino acids.

  • Doubling time: 10 minutes under optimal conditions.

• Infective Dosage: Requires large numbers (> 10^6 to 10^7 cells/g).

3.2. Toxicoinfection by C. perfringens

• Incubation Time: 8 to 16 hours.

• Symptoms:

  • Diarrhea,

  • Severe abdominal cramps.

• Pathway:

  • Contamination → Growth from temperature abuse → Ingestion → Growth in intestines → Toxin release.

3.3. Pigbel Disease

• Symptoms: Vary from mild diarrhea to severe abdominal pain, bloody stool, and potential septic shock.

4. Clostridium botulinum

• Characteristics:

  • Motile,

  • Optimal temperature: 30 to 40°C.

  • Contaminates low acid foods, especially meats and fish.

  • Growth inhibited at pH ≤ 4.5.

• Toxin Production:

  • Produces the most potent neurotoxin known (BoNT).

  • LD50: 30 M mice LD50/mg.

  • Mortality rate for botulism: 30 to 65%.

4.1. Types of Botulism

• Types:

  • Foodborne,

  • Infant,

  • Wound,

  • Adult intestinal toxemia.

  • Iatrogenic - napadami sa medical intervention

4.2. Symptoms of Foodborne Botulism

• Incubation Time: 12 – 72 hours (average 18-36 hours).

• Symptoms:

  • Muscle weakness,

  • Difficulty in swallowing and breathing,

  • Paralysis,

  • Nausea, vomiting, and abdominal pain.

• Mechanism:

  • Toxin affects the nervous system, causing flaccid paralysis.

4.3 Infant botulism

• Ingestion of 10-100 spores

• Spores germinate, grow, produce toxin in intestines of the baby

• Symptoms : constipation weak sucking, weak cry, poor feeding, lethargy, loses head then limb control