FIE Lesson 1 Introduction to Food Microbiology 2024 PDF

LEGISLATION, HYGIENE AND APPLIED MICROBIOLOGY FOR FOOD SAFETY Introduction to Applied Food Microbiology Luca Fasolato Università degli Studi di Padova Dipartimento di Biomedici...

LEGISLATION, HYGIENE AND APPLIED MICROBIOLOGY FOR FOOD SAFETY Introduction to Applied Food Microbiology Luca Fasolato Università degli Studi di Padova Dipartimento di Biomedicina Comparata e Alimentazione This lesson is about fundamentals of food microbiology; second part is related to the description of Foodborne disease, the classification of intoxication, infection and mixed forms. 1  Foodborne Pathogens Induction of a more or less severe clinically evident syndrome (food-borne illness) Generally very low load in Food Not induction of changes in the sensory characteristics of the food The Bad Foodborne Disease Induction of a Clinically Evident Syndrome Foodborne diseases are caused by the consumption of contaminated food and can lead to a range of clinical symptoms. The severity of these symptoms can vary significantly, depending on the pathogen involved and the individual's health. Some common symptoms include nausea, vomiting, diarrhea, and abdominal pain. In more severe cases, foodborne illnesses can lead to serious complications and hospitalization. Generally Very Low Load in Food Despite the potential for severe health effects, many foodborne pathogens can be present in very low concentrations. This low load can make it difficult to detect contamination during food safety inspections, as traditional testing methods may not identify pathogens that are present in small amounts. It underscores the importance of consistent hygiene practices and thorough cooking to mitigate risks. No Induction of Changes in Sensory Characteristics of the Food (no spoilage)  Biological hazard: Pathogens in food MOs that can cause harm to the consumer: foodborne diseases Not only bacteria….More than 250 species are involve in foodborne disease Here you can see one list of possible biological hazards that are present in foods. A large number of foodborne disease are related to the consumpition of food contamianted with bacteria, however, also viruses an parassites are important biological hazards. 3  Bacterial Foodborne Pathogens Salmonella spp. ENTEROBACTERIACEAE E. coli STEC Yersinia spp. GRAM - Vibrio Campylobacter spp. Staphylococcus aureus Listeria monocytogenes GRAM + Clostridium spp. SPORE-Forming Bacillus cereus The Bad These are the most common bacteria involve in foodborne disease 4  Foodborne disease – foodborne illness Calssification of FBD Some causes of FBD FBD pathogens are not involved in food spoilage! Disease of an infectious or toxic nature caused, or which is supposed to have been caused, by consumption of food or water Acute/chronic disease that are relative due to gastrointestinal symptoms, chronic ones are usually more serious and due to organic neurological resentments such as guillain-barré syndrome, neuropathy or reactive arthritis A correct and accurate investigation of food-borne diseases requires knowledge of the fundamentals relating to this type of pathology. The definition that can be given of them is: Disease of an infectious or toxic nature caused, or which is supposed to have been caused, by consumption of food or water. 5 Why is it important to classify FoodBorne Diseases - FBD? CONSUMERS We may provide useful information to our doctor We may provide useful information to the competent authorities Food Business Operator Withdrawal/recall the product’s Lot from the market To Formulate hypotheses of contamination –root cause analysis 6  Factors that Contribute to Outbreaks of Foodborne Disease Virulence of the MO→ strain dependents; linked to virulence factors Infectious load / dose reached in food MO Ability to adhere to mucous membranes, 3 LogCFU/g Listeria 6 LogCFU/g Salmonella invasiveness, etc. Intrinsic Environmental factors (pH, aw..) Type of food consumed: e.g. fat, small FOOD volumes, liquids Extrinsic factors: the patient - eg gastric pH YOPI (Young Old Pregnant and Consumer Immunodeficient) Factors Influencing the Virulence of Microorganisms in Foodborne Illness Virulence of the Microorganism The virulence of a microorganism (MO) is often strain-dependent and closely linked to various virulence factors. These factors can include toxins, adherence mechanisms, and the ability to evade the host's immune response. Understanding these aspects is crucial, as they determine the potential severity of the infection. Infectious Load / Dose Reached in Food The infectious dose refers to the quantity of a pathogen that must be ingested to cause infection in a susceptible host. This is typically measured in log10 Colony Forming Units (CFUs). Different pathogens have varying infectious doses; some can cause illness with a relatively low number of organisms, while others require a higher load. This measure is directly related to the virulence of the microorganism, as a higher infectious load increases the likelihood of illness. Ability to Adhere to Mucous Membranes and Invasiveness Pathogens possess specific mechanisms that enable them to adhere to mucous membranes in the gastrointestinal tract. This adherence is crucial for colonization and subsequent invasion of host tissues. The degree of invasiveness can vary among strains, influencing how easily a pathogen can establish an infection and cause disease. 7 Intrinsic Environmental Factors Several intrinsic environmental factors affect the survival and virulence of pathogens in food. These include pH, water activity (aw), and temperature. For instance, most pathogens thrive in neutral to slightly acidic environments, while extreme pH levels can inhibit their growth. Similarly, low water activity can limit microbial growth, making food preservation techniques essential for food safety. Type of Food Consumed The type of food consumed plays a significant role in the risk of foodborne illness. Foods high in fat or those that are liquid can favor the survival of microorganisms along the gastric barrier, also small amount of materials could be a vehicle. Extrinsic Factors: The Patient Extrinsic factors, such as the individual consuming the food, also influence the likelihood of infection. For example, the gastric pH can vary significantly between individuals, affecting how well pathogens survive the stomach's acidic environment. Certain populations, such as the Young, Old, Pregnant, and Immunodeficient (YOPI), are particularly susceptible to foodborne illnesses due to their compromised immune systems or physiological changes 7  Foodborne poisoning Foodborn disease – foodborn illness 1. Foodborne infections 2. Foodborne intoxication 3. Mixed forms (infection-intoxication) Any food-related outbreak where two or more people show signs of illness. With the exception of intoxication by Clostridium botulinum, fungi and other natural or chemical toxic agents in which the presence of only one case is considered as outbreak Acute pathology and chronic pathology 1. Foodborne infections 2. Foodborne intoxication 3. Mixed forms (infection-intoxication) 1.. With the exception of intoxication by Clostridium botulinum, fungi and other natural or chemical toxic agents in which the presence of only one case is sufficient 8  FOODBORNE INFECTIONS Foods can carry pathogens; the FBD could be also transmitted by fecal-human ways (e.g. Salmonella and Listeria) Bacteria can survive in foods and in most cases is not necessary the replication of cells to reach the infectious dose - Low infectious dose = few cells are able infecting humans - Invasion and multiplication inside/surface of the intestinal mucosae= Bloody diarrhea and/or infections/damage to other organs (e.g. kidney) - Long time for symptoms, fever = generic symptoms - Systemic infection= blood system→ bacteremia→ other organs (Salmonella Typhoidal) Food-borne infections are classical illnesses transmitted by the food consumption. However also the inter-human transmission is important. In general, the multiplication of pathogens are not necessary inside the food because the infecting dose is usually low. This is not always true , for example Salmonella usually has an high infecting dose at around 4 or 5 logarithms per grams. After the gastric barrier , bacteria are able to colonize the intestinal membrane while a bloody diarrhea occurs. Symptoms are generics and take time to develop fever. Many pathogens are also systemic, illnesses can involve other part of the body. Systemic infection= All the organism- body (Salmonella typhoidal) Foodborne infection is caused by the ingestion of food containing live bacteria which grow and establish themselves in the human intestinal tract 9  FOODBORNE INTOXICATION FBD is determined by the ingestion of food containing toxins (as result of microbial growth) the illness depends only on the toxin formed in the food No fever → Symptoms appear in few hours It is not necessary the precence of MO Botulinum intoxication Cl. botulinum Staphylococcus aureus Staphylococcal intoxication Preformed toxin No Fever → Symptoms Appear Within a Few Hours Foodborne intoxication occurs when toxins produced by bacteria are ingested, leading to symptoms that typically appear within a few hours. The minimum initial load of pathogens required to produce toxins is generally between 10³ to 10⁴ CFUs/g. Importantly, the food may or may not contain the bacterium itself; it is the toxins that induce the illness. The incubation period is relatively short, ranging from approximately 2 to 6 hours. Toxins associated with foodborne illnesses include those from Staphylococcus aureus, Bacillus cereus, Clostridium botulinum, as well as fungal toxins, nitrites, histamine, and okadaic acid. The presence of the bacterium itself in the food is not necessary; instead, the bacterium can produce toxins directly in the food. These toxins are usually thermostable, meaning they can resist heat treatments that may otherwise kill the bacteria. As a result, even if the bacterium is not present in the food at the time of consumption, it can still have an effect later on. For instance, Staphylococcus aureus can preform toxins, which can cause symptoms like nausea, vomiting, and diarrhea within 1 to 6 hours after ingestion. Furthermore. In summary, foodborne intoxication is primarily caused by ingesting food containing preformed toxins from bacterial growth, rather than the live microorganisms 10 themselves. 10  MIXED FORMS (INFECTION-INTOXICATION) Caused by FB which manifest their pathogenic action only after multiplication inside food before Food = it is substrate for microbial multiplication where it is possible also the toxins release FBP can grow inside/surface of the intestine producing toxins C.perfringens Bacillus cereus (emetic toxin) B.cereus (enterotoxin) Infant botulism Toxin inside the food Toxin relesed inside the body The third type of foodborne disease is known as mixed infection-intoxication. In this case, there must be live and viable bacteria present in the food, with concentrations typically ranging from 10⁴ to 10⁶ CFUs. The release of toxins occurs after ingestion, leading to a medium to long incubation period, which can range from 48 to 72 hours, and in some cases, up to 2 months, with an average of around 72 hours. In mixed infection-intoxication, there is simultaneous production of toxins and the development of the bacterium. Both the growing bacteria and the toxins produced contribute to the symptoms observed. For example, Bacillus cereus, a spore-forming, motile Gram-positive rod, can cause either intoxication or infection. It produces an emetic toxin under specific conditions in food. Its spores can withstand boiling temperatures, such as in rice, allowing it to survive cooking. When the rice is stored improperly (thermal abuse), the bacteria can grow and produce toxins at temperatures above 12°C. Notably, the toxin is resistant to heat, surviving temperatures up to 126°C, which means that improperly cooked rice cannot be rendered safe. If someone ingests rice used in sushi after a few hours of improper storage, they may experience vomiting syndrome due to the emetic toxin. Food poisoning from such toxins typically has a faster onset than infections, with symptoms appearing within 1 to 6 hours after ingestion, often resolving quickly. In 11 contrast, Bacillus cereus can also lead to an enteric form of illness if a sufficient concentration is consumed, allowing it to replicate and produce enterotoxins, which, although sensitive to heat and proteolytic enzymes, stimulate the accumulation of fluid in the intestine. Infant botulism, on the other hand, occurs in infants or young children when the bacterium grows in their intestinal mucosa, producing the toxin locally after the ingestion of honey. The toxins can be classified into two categories: endotoxins, such as lipopolysaccharides, which are released upon the death of the bacterium, and exotoxins, such as proteins and enzymes, which are released during the organism's life. 11  Foodborne diseases Foods that contain Foods that contain Foods that contain microorganisms that poisonous chemicals or pathogenic multiply in the intestine toxins produced by microorganisms and produce toxins microorganisms Food Food Food Poisoning Infections Toxinfections 12  How to recognize FBD? infections vs intoxication Infections Intoxication Organisms Bacteria toxins Virus Parassites invasion to the mucosae meccanisms of action and infection specific action incubation time hours-days minute-hours Symptoms Diarrhea Diarrhea Vomit Vomit Fever Nausea Nausea breathing difficulties neurological problems transmission also Inter-human not trasmissible cross contamination - lack cross contamination - lack in Factors affecting in hygienic practices - lack hygienic practices - lack in contamination in treatments refrigeration Differences Between Infection and Intoxication In summary: infections and intoxications. Although both can cause similar symptoms, there are fundamental differences in their mechanisms of action, causes, and onset times. Infections Foodborne infections are caused by the presence of microorganisms such as bacteria, viruses, or parasites that invade the gastrointestinal system. These organisms penetrate the mucosal lining and cause infection. The incubation period can vary from hours to days, depending on the pathogen involved. Typical symptoms include: Diarrhea Vomiting Fever Nausea Breathing difficulties Neurological problems Infections can also be transmitted from person to person, which increases the risk of outbreak scenarios. Intoxications In contrast, foodborne intoxications occur due to the ingestion of preformed toxins 13 present in food. These toxins can result from the growth of bacteria or other microorganisms. The incubation period for intoxications is much shorter, ranging from minutes to a few hours. Symptoms include: Diarrhea Vomiting Nausea Intoxications are not transmissible from person to person, as the illness develops solely from consuming contaminated food. Factors Affecting Contamination Both infections and intoxications can be influenced by contamination factors. Cross- contamination, lack of hygienic practices, and inadequate treatment are common issues in both cases. However, for intoxications, lack of refrigeration is a crucial factor, as the growth of toxin-producing microorganisms can occur rapidly under uncontrolled conditions. In summary, while infections arise from the invasion of microorganisms, intoxications are caused by the ingestion of toxins. Understanding these differences is essential for developing effective prevention and management strategies for foodborne illnesses. 13 Let's analyze real cases – Active learning moment THE CASE IDENTIFY THE CAUSE CLASSIFY SHARE WITH THE CLASS WHAT IT INVOLVES? WORST HOME PRACTICES FUTURE APPLICATION → FOOD CHAIN 14  Food contamination CROSS-CONTAMINATION It occurs when infectious agents are transmitted from one food to another through Objects Surfaces Hands of operators knives work tables meat grinder containers Various equipment Cross-Contamination Cross-contamination is a critical concept in food safety that refers to the transfer of harmful microorganisms or contaminants from one surface to another, particularly through food. This can occur when contaminated utensils, cutting boards, or surfaces come into contact with clean food items, leading to the spread of pathogens. It is essential to prevent cross- contamination by practicing proper hygiene, such as washing hands and sanitizing surfaces, and by using separate utensils for raw and cooked foods. Effective prevention measures are crucial to reduce the risk of foodborne illnesses. 15  Food contamination EXEMPLES OF CROSS CONTAMINATION Vegetables with a microbial higher load, but environment does not allow the growth Red meat Vegetables On the poultry sourfaces there are phatogens as Salmonella Poultry meat On cooked food the recontamination is particular dangerous because it will not processed again Cooked products Raw poducts Examples of Cross-Contamination 1.Vegetables with a High Microbial Load: Vegetables can sometimes have a higher microbial load due to soil contamination or improper handling. If these contaminated vegetables come into contact with raw meat, they can transfer pathogens to the meat, posing a risk of foodborne illness, especially if the environment doesn’t support microbial growth (e.g., refrigeration). 2.Poultry with Salmonella: Raw poultry is often a source of Salmonella, a harmful bacterium. If raw poultry is handled without proper hygiene and comes into contact with red meat (like beef or pork), it can transfer Salmonella to the red meat. This cross-contamination can lead to serious health risks if the meat is not cooked properly. 3.Raw to Cooked Products: One of the most problematic forms of cross- contamination occurs when raw foods come into contact with cooked products. For instance, if a cutting board used for raw chicken is not cleaned thoroughly before being used to slice cooked vegetables, any remaining pathogens can contaminate the cooked food. This is particularly concerning because cooked foods are often ready to eat and should be free of harmful microorganisms. 16  Time and temperature In any way and at any stage microbial contamination of food the risk is related to Time Temeprature of conservation from the preparation Perishable food Microbial contamination of food poses risks at any stage, and several key factors contribute to this risk: 1.Perishable Foods: Perishable foods are those that have a high level of available water (water activity) and typically a higher pH, making them more conducive to microbial growth. Foods such as fresh fruits, vegetables, dairy products, and meats fall into this category. The high water activity allows microorganisms to thrive, increasing the likelihood of contamination and spoilage if these foods are not handled properly. 2.Preparation in Advance: Preparing food in advance can pose risks if proper food safety practices are not followed. When food is prepared and then left at room temperature or not adequately refrigerated, it provides an opportunity for microorganisms to multiply. This is particularly problematic for perishable items, as their extended exposure to unsafe temperatures can lead to significant growth of harmful pathogens. 3.Temperature of Storage: The temperature at which food is stored is a crucial control point for preventing microbial growth. Foods should be kept at safe temperatures to inhibit the growth of bacteria. The "danger zone" for food safety is typically between 40°F (4°C) and 140°F (60°C), where bacteria can multiply rapidly. Effective refrigeration and freezing practices can greatly reduce the risk of 17 contamination. 4. Thermal Abuse: Thermal abuse occurs when food is not kept at safe temperatures during cooking, cooling, or storage. This can lead to outbreaks of foodborne illnesses, as it allows bacteria to grow unchecked. For example, if cooked food is left out for too long or not reheated to the proper temperature before serving, it can become a breeding ground for pathogens. In summary, managing temperature during storage and preparation, as well as understanding the properties of perishable foods, is essential for minimizing the risk of microbial contamination and ensuring food safety. 17  Root-cause analysis – home work activity At home: Define the information needed to conduct a root-cause analysis Deadline: Two weeks Modality of work: Autonomous research of content followed by group discussion and comparison Expected time: 3 hours for collecting information and managing data; 1 hour for discussion and comparison Root cause analysis is a systematic approach used to identify the underlying causes of problems or incidents. 18  Steps of activity 1. Initial material: We will start with a detailed newspaper article on one of the case studies. 2. Research: I will ask you to search for additional online information about the case, including official statements, analysis reports, and relevant articles. (individual activity – at home) 3. Use of ChatGPT or AI: You will start to formulate effective prompts to get useful responses from ChatGPT. For example, "What are the main causes of this food contamination case?" or "How can I identify the root cause of a product recall?“(individual activity – at home ) 4. Compile and analyze data: You will use the information gathered to complete the Root Cause Analysis Framework provided in moodle, answering all the questions. (in group activity – at home – you can use AI) 5. Class discussion: I will organize a discussion session where you will present their findings and compare them with those of the professor. (in group activity – in class) 1 slide 1 minute of explanation by your leader 6. Feedback and reflection: I will provide feedback, and we will compare our results. We will also share ideas about this activity and how they can apply these skills in the future. (in class) 19 ACTIVITY 1 Paradox: Increase of foodborne disease despite advances in science and in hygiene practices Why? 3-4 minutes of personal commentary on a topic Personal reflection 7.5% (420,000 death) of all deaths annually are due to foodborne illnesses (WHO 2020) Food unsafe for consumption causes 600 million cases of foodborne diseases and 420,000 deaths every year, and 56 million people die each year (Ritchie and Roser, 2018; WHO, 2015). This data indicates that 7.69% (600 million) individuals of world populations (7.8 billion) suffer from foodborne diseases every year and 7.5% (420,000 death) of all deaths (56 million) annually are due to foodborne illnesses. This is almost equivalent to 31.1% of annual deaths caused by road traffic accidents (1.35 million) worldwide (WHO, 2020). 20  Changing of the food microbiota Consumers preference: Increased consumption of RTE - Ready to eat food; o RTC – Ready to cook food: CONTAMINANTS not eliminated by cooking Food Technology Presence of packaging and changes in the atmosphere close to the food (MAP – modified atmosphere; SV – vacuum) Reduction of some bacterial species (spoilers) with increase of others (pathogens) due to sanitization treatments Increased manipulations with consequence of modification of the microbiota in the fresh product and increased risks of contamination with new microorganisms 21  Changing of the food microbiota Economic Very long shelf life Long transfer of food (import-export) Improved techniques in food analysis More effcient and sensitive detection (Virus, Campylobacter) Effect of human actions Changing of the climat Diffusion of chemical and toxic compounds in the environment (AR, mutation) This fall can probably be attributed to the indirect impact of the COVID-19pandemic on both the true occurrence of FBO in the population and the reduced capacity to detect,investigate and report FB 22  Emerging Pathogens 1. E. coli producers of verocytotoxin VTEC (from 1982) 2. Listeria monocytogenes: meningitis in immunocompromised hosts 3. Campylobacter jejuni from 1970, cause of diarrhea (today it is the second zoonotic agent – poultry water) 4. Salmonella and Staphylococcus aureus: emergence of multidrug-resistant strains 5. Spores (pathogens and spoilers bacteria) resist treatments and develop thanks to longer shelf life Mutazioni, oppure cambiamento dei disinfettanti nella filiera produttiva o delle techiche di produzione. 23