Introduction to Applied Food Microbiology

Introduction to Applied Food Microbiology

• This lesson covers fundamental food microbiology, and the description of foodborne illnesses, including intoxication, infection, and mixed forms.

Foodborne Pathogens

• Foodborne pathogens cause clinically evident syndromes (foodborne illnesses).
• The severity of symptoms varies depending on the pathogen and individual health.
• There is generally a very low pathogen load in food.
• Sensory characteristics of the food are not altered (no spoilage).

Biological Hazard: Pathogens in Food

• Includes various microorganisms that can cause harm to the consumer, not only bacteria, but also viruses and parasites.
• A lengthy list of pathogens is included: Clostridium botulinum, Clostridium perfringens, Bacillus cereus, Brucella abortus, Brucella suis, Campylobacter spp., pathogenic Escherichia coli, Listeria monocytogenes, Salmonella spp., Shigella, Staphylococcus aureus, Streptococcus pyogenes, Vibrio cholera, Vibrio parahaemolyticus, Vibrio vulnificus, Yersinia enterocolitica, Hepatitis A and E, Norwalk virus group, Rotavirus, Cryptosporidium parvum, Diphyllabothrium, Entamoeba histolytica, Giardia lamblia, Ascaris lumbricoides, Taenia solium, Taenia saginata, and Trichinella spiralis.

Bacterial Foodborne Pathogens

• Divided into Gram-positive and Gram-negative categories.
• Common bacteria implicated in foodborne illness are Salmonella spp., E. coli STEC, Yersinia spp., Vibrio, Campylobacter spp., Staphylococcus aureus, Listeria monocytogenes, Clostridium spp., and Bacillus cereus.

Foodborne Disease Classification

• Acute or chronic diseases with various symptoms stemming from gastrointestinal irritation to neurological disorders such as guillain-barré syndrome, neuropathy, or reactive arthritis.
• Disease of an infectious or toxic nature caused by food or water consumption.
• Pathogens are not involved in food spoilage.

Why Classify Foodborne Diseases?

• To yield useful knowledge to physicians and competent health authorities.
• To enable withdrawals/recalls of contaminated food lots.
• To generate hypotheses for contamination root cause analysis.

Factors Contributing to Foodborne Disease Outbreaks

• Virulence of the microorganism: Strain dependent and linked to factors like toxins, adherence mechanisms, and ability to evade the host's immune response.
• Infectious load/dose: The amount of pathogen required to cause illness.
• Ability to adhere to mucous membranes and invasiveness: Important for colonization, invasion of tissues and disease establishment.

Intrinsic Environmental Factors

• Factors in the food influencing pathogen survival and virulence include pH, water activity (aw), and temperature.
• These factors can influence microbial growth in food.

Type of Food Consumed

• The type of food consumed plays a significant role in the risk of foodborne illness, including high-fat foods and liquids.
• Extrinsic factors within the patient can also influence, such as gastric pH levels.
• Individuals with compromised immune systems can be more susceptible.

Classification of Foodborne Diseases

• Foodborne infections: Microorganism grows inside body and causes disease
• Foodborne intoxication: Bacteria produce toxins before it is ingested.
• Mixed forms (infection-intoxication): Simultaneous bacterial growth inside body, and toxin production in the food.

Foodborne Infections

• Bacteria, viruses or parasites multiply inside gastrointestinal system.
• Illness develops a few hours to days after ingestion.
• Infection can be transmitted from person to person.
• Factors influencing contamination include cross-contamination, poor hygiene, lack of sanitation and refrigeration.

Foodborne Intoxication

• Illness develops from toxins produced in food before ingestion.
• Symptoms show up within minutes to hours.
• No presence of live microorganisms is required to cause symptoms.
• Toxins associated with this illness can include that of Staphylococcus aureus, Bacillus cereus, Clostridium botulinum, fungal toxins, nitrites, histamine.
• Temperature factors influence the toxins' generation and survival.

Mixed Forms (Infection-Intoxication)

• Symptoms (usually diarrhea and vomiting) develop 48–72 hours after ingestion, sometimes up to 2 months.
• Bacteria is present in the food, and toxins are produced after ingestion.
• Bacillus cereus is example of a mixed infection-intoxication pathogen.

Cross-Contamination

• The transfer of harmful microorganisms from one food to another.
• Can occur via objects (e.g., knives, cutting boards), surfaces (e.g., work tables), or hands of food handlers.
• Key to prevent: cleaning and sanitizing surfaces, using distinct utensils, and practicing proper hygiene.

Time and Temperature

• Microbial contamination risk is associated with factors like water activity and pH of various foods leading to quicker growth of microorganisms.
• Foods are typically classified as perishable or non-perishable based on the water activity.
• Temperature control during storage and preparation is essential for food safety, preventing the growth of harmful bacteria.

Thermal Abuse

• Occurs when food are not kept at safe temperatures during cooking, cooling, or storage.
• Food left out at room temperature for long periods allows microbial growth, causing foodborne illnesses

Root-Cause Analysis

• Method for identifying underlying causes of problems of food contamination.
• Collect data via home research.
• Group discussion and compare results.
• Feedback and reflection on how to improve the skills in future.

Changing of the Food Microbiota

• Consumers preference for ready-to-eat or ready-to-cook foods has increased, requiring careful assessment of the implications for microbial safety.
• Factors contributing to changing microbiota include, food packaging, atmosphere close to the food, reduction in some species (spoilers), and increase in others (pathogens).
• Increased food-handling and manipulating activities can influence microbial diversity and increase risk of contamination (food safety compromised).

Emerging Pathogens

• Includes new bacteria, viruses and parasites.
• E. coli, Listeria monocytogenes, Campylobacter jejuni, Salmonella, and Staphylococcus aureus are emerging as multidrug-resistant strains thanks to longer shelf life.

Activity 1- Paradox

• Foodborne illness incidence despite advancements in science and hygiene is a paradox.
• 7.5% of all deaths worldwide are caused by foodborne illnesses, a figure comparable to significant road traffic accidents.

This quiz covers the basics of applied food microbiology, including foodborne illnesses and their causes, such as intoxications and infections. Learn about various foodborne pathogens, their symptoms, and the impact they have on food safety without altering sensory characteristics. Test your knowledge on the microorganisms that pose biological hazards in food.