2.1 Biological Contaminants

Biological contaminants are the leading cause of foodborne illness—accounting for over 90% of all outbreaks. These are living organisms (or substances produced by living organisms) that make food unsafe to eat. Understanding how these pathogens grow and spread is essential to preventing foodborne illness.

The Four Types of Biological Hazards

1. Bacteria - Single-celled organisms that can multiply rapidly in food

• Most common cause of foodborne illness
• Some produce heat-resistant spores
• Some produce dangerous toxins

2. Viruses - The smallest of biological contaminants

• Don't grow in food, but can contaminate it
• Spread person-to-person or through contaminated water
• Responsible for more than half of all foodborne illness cases (e.g., Norovirus)

3. Parasites - Organisms that live in or on another organism

• Often transmitted through contaminated water or undercooked food
• Examples: Giardia, Cryptosporidium, Anisakis (found in fish)

4. Fungi - Includes molds and yeasts

• Some produce dangerous toxins (mycotoxins)
• Visible mold on food means it should be discarded
• Cannot be killed by cooking once toxins are present

For the Exam: Know the four types of biological hazards. Most questions focus on bacteria and viruses, but parasites and fungi appear on the exam too.

FAT TOM: Six Conditions for Bacterial Growth

Bacteria need specific conditions to grow and multiply. Remove any one of these conditions, and you can prevent or slow bacterial growth. Remember the acronym FAT TOM:

Key Insight: You can't always control all six FAT TOM conditions, but you must control at least one. Temperature and time are the easiest to control in food service.

The Bacteria Growth Curve

When bacteria find favorable conditions, they follow a predictable growth pattern:

1. Lag Phase (0-4 hours)

• Bacteria adapt to new environment
• Little to no growth during this period
• Critical window: This is when proper cooling matters most

2. Log Phase / Exponential Growth (4-12 hours)

• Bacteria multiply rapidly—doubling every 10-20 minutes
• Population explodes from hundreds to millions
• Most dangerous phase: Food becomes unsafe quickly

3. Stationary Phase (12+ hours)

• Growth slows as nutrients run out
• Bacteria die at the same rate they multiply
• Toxins may accumulate to dangerous levels

4. Death Phase

• Nutrients depleted; waste products toxic
• More bacteria die than multiply
• Warning: Toxins may remain even after bacteria die

For the Exam: Know that bacteria can double every 20 minutes in the log phase when conditions are ideal. This is why the 4-hour rule exists—to keep food out of the log phase.

The Big Six Pathogens

The FDA has identified six highly contagious pathogens that cause severe illness and are easily transmitted through food by infected workers. These are called the Big Six, and they require special reporting and exclusion policies.

Critical Rule: If a food handler is diagnosed with any of the Big Six, they must be excluded from the operation and cannot return without written medical clearance from a healthcare provider and approval from the local health department.

Spore-Forming Bacteria

Some bacteria can form spores—a protective shell that allows them to survive extreme conditions:

Spore Characteristics:

• Resistant to heat, cold, drying, and chemicals
• Can survive cooking temperatures that kill normal bacteria
• "Wake up" when conditions improve (warmth, moisture)

Common Spore-Formers:

• Clostridium perfringens - "Cafeteria germ"; thrives in large batches held at wrong temperatures
• Clostridium botulinum - Causes botulism (rare but deadly); found in improperly canned foods, garlic-in-oil mixtures
• Bacillus cereus - Associated with cooked rice left at room temperature

Prevention Strategy:

• Can't kill spores by normal cooking - Must prevent growth after cooking
• Cool food rapidly (135°F to 70°F in 2 hours, then 70°F to 41°F in 4 more hours)
• Keep hot foods hot (135°F+) and cold foods cold (41°F or below)
• Discard food held in danger zone too long

Bacterial Toxins

Some bacteria produce toxins (poisons) that cause illness:

Intoxication - Illness caused by eating toxins produced by bacteria

• Staphylococcus aureus - Toxin causes rapid-onset vomiting (30 minutes to 6 hours)
• Clostridium botulinum - Produces deadly botulinum toxin (nerve poison)
• Bacillus cereus - Produces emetic toxin (causes vomiting)

Key Difference: Infection vs. Intoxication

For the Exam: Remember that toxins are NOT destroyed by cooking. Once Staphylococcus aureus produces toxins in food, reheating won't make it safe.

Preventing Biological Contamination

Control Temperature:

• Keep cold food at 41°F or below
• Keep hot food at 135°F or above
• Minimize time in danger zone (41°F-135°F)

Control Time:

• Follow the 4-hour rule
• Use two-stage cooling method
• Label and date TCS foods

Prevent Cross-Contamination:

• Separate raw and ready-to-eat foods
• Use separate cutting boards and utensils
• Clean and sanitize between tasks

Practice Good Hygiene:

• Exclude/restrict sick employees (especially Big Six)
• Require proper handwashing
• No bare-hand contact with ready-to-eat food

Purchase from Safe Sources:

• Buy from approved, inspected suppliers
• Inspect deliveries for time-temperature abuse
• Reject suspicious food