Normal Flora Lecture 2 Part 1 - PDF

Normal flora of the oral cavity By Assistant Professor Raed Taha Alneama Department of basic sciences College of dentistry University of Basrah Objectives - Define bacterial oral flora - Scope on normal flora - Study the association between human and oral ca...

Normal flora of the oral cavity By Assistant Professor Raed Taha Alneama Department of basic sciences College of dentistry University of Basrah Objectives - Define bacterial oral flora - Scope on normal flora - Study the association between human and oral cavity microbiota - Define factors that influence the oral ecosystem - Significant of the normal flora to the host  What are Normal Flora? Normal flora are microorganisms (bacteria, fungi, protozoa, and viruses), mostly bacteria that continuously inhabited the human body (Resident normal flora). Under normal conditions in a healthy human, they are harmless and may even be beneficial. Also called Commensals  Normal Flora A fetus is sterile when born (No normal flora), then newborn start having the normal flora from its mother, air, food and the environment. Our internal organs are sterile such as spleen, liver, pancreas, bladder, CSF and blood unless during infection. Normal flora differ from one human to another depending on age, diet, and geographic habitat. When the number of resident normal flora is greatly reduced, opportunistic microbes can easily cause infections in these areas e.g. Candida albicans that cause candidiasis.  Why Should We Know About Normal Flora? We all should know about the types and distribution of normal flora in our bodies because: 1. It gives us better understanding of the possible infections that result from injury to a specific body site. 2. Human Health: Is crucial for maintaining good health because these microorganisms play a significant role in digestion, immune system development, and protection against harmful pathogens. Imbalances in the normal flora can lead to health issues. 3. Digestive Health: Normal flora in the gut, such as beneficial bacteria like Lactobacillus and Bifidobacterium, help with digestion and the absorption of nutrients. They also play a role in preventing the overgrowth of harmful bacteria. 4. Immune System Development: Exposure to various microorganisms in our environment helps our immune system develop and differentiate between harmful and harmless substances. This development is critical for a strong and balanced immune response. 5. Disease Prevention: A healthy normal flora can help prevent the colonization of harmful pathogens by competing for resources and producing substances that inhibit the growth of these pathogens. 6. Medical Diagnoses: Knowledge of normal flora is important in the medical field for diagnosing infections. It helps differentiate between infections caused by harmful pathogens and those caused by the normal flora. This is particularly relevant in clinical microbiology. 7. Probiotics and Prebiotics: Understanding normal flora has led to the development of probiotics (beneficial microorganisms) and prebiotics (substances that promote the growth of beneficial microorganisms). These are used to maintain or restore a healthy balance of microorganisms in the body. 8. Research and Therapeutics: Research on the normal flora has led to discoveries about the role of microorganisms in various diseases, including gastrointestinal disorders, autoimmune diseases, and even mental health conditions. This knowledge can lead to the development of new therapeutic approaches. Some of the normal flora are - Indigenous or resident flora - Refers to the - microorganisms that are a permanent part of the oral cavity's microbial community and are compatible with the host. - Exogenous flora - Bacteria not part of the normal - flora of the oral cavity and thought to cause disease. These bacteria, come from external sources and temporarily colonize the mouth. - Transient flora - Organisms which are only in the oral cavity for short period of time. Those microorganisms are not considered as a part of the permanent or resident oral microbiota. Where Can We find Normal Flora? Resident normal flora are found in sites exposed to the outside world (external environment). 1. Skin 2. Eyes and Ears 3. Respiratory Tract 4. Oral Cavity (Mouth) 5. Gastrointestinal Tract 6. Urogenital Tract  Oral Cavity (Mouth) They have both aerobic and anaerobic bacteria like: C. diphtheroides, S. aureus, and S. epidermidis. Also yeasts, molds, protozoa, and viruses can be living in the mouth. For example:- Teeth and Gengiva: S. mutans Poor dental hygiene help bacteria to grow and cause infection like dental caries and gingivitis. After dental surgeries, there might be a risk of bloodstream infection that might cause endocarditis. Four ecosystems are present in the oral cavity Buccal epithelium Dorsum of the tongue Supragingival tooth surface Subgingival tooth and crevicular epithelial surfaces The buccal epithelium has more of gram-positive streptococci in contrast to tongue which has more of gram- positive filaments. The subgingival region is essentially anaerobic as compared to the supragingival region. - These ecosystems interact and influence each other, and maintaining a balanced oral microbiome is essential for oral health. - Proper oral hygiene practices, such as regular brushing, flossing, and dental check-ups, help keep these ecosystems in balance.  Factors influencing the oral ecosystem The growth of oral microorganisms is influenced by a variety of factors such as: 1-Temperature 2-pH 3- Oxidation –reduction potential 4- The availability of nutrients and water 5-The anatomy of oral structures 6 -Host factors which include host defense mechanisms, age, hormonal changes stress and genetic factors. 7-Other factors such as diet, oral hygiene, antimicrobial agents, drug and diseases. 8- Bacterial Factors.  Significant of the normal flora to the host Beneficial functions of normal flora 1. Protect our organs and systems that have direct contact with the external environment from invading pathogens. Some normal flora produce substances that kills pathogens and others compete for with them for nutrients. 2. In newborns, normal flora stimulates the development of immune system. 3. Normal flora of the gut, provides important nutrients such as vitamin K which aid in digestion and absorption of nutrients. 4. Protection Against Pathogens: By occupying ecological niches and competing with harmful microorganisms, normal flora can prevent the overgrowth of pathogenic bacteria and fungi, reducing the risk of infections. 5. Fermentation: Fermentation of undigested food residues by gut bacteria produces short-chain fatty acids (SCFAs) like acetate and propionate. SCFAs provide an energy source for the colon cells and have anti-inflammatory properties. 6. Detoxification: Normal flora can detoxify harmful substances and drugs, aiding the liver in its detoxification processes. 7. Digestion and Nutrient Absorption: Gut bacteria help break down complex carbohydrates, ferment dietary fibers, and aid in the digestion of certain foods, which enhances nutrient absorption.  Significant of the normal flora to the host Harmful effect of normal flora 1. When the normal flora are displaced from their normal site of the body e.g. bloodstream infections by S. epidermidis. 2. When potential pathogens gain a competitive advantage due to diminished populations of harmless competitors e.g. C. difficile growing in the gut after antibiotic therapy. Dysbiosis, an abnormal shift in microbial populations, can lead to various health problems, including gastrointestinal issues and inflammatory disorders. 3. When individuals are immunocompromised, normal flora can overgrow and become pathogenic. 4. Opportunistic Infections: Some normally harmless bacteria can cause infections when the immune system is compromised. For example, Candida albicans, a fungus that's part of the normal flora, can cause yeast infections in the mouth, throat, or genitals in individuals with weakened immune systems. 5. Oral Health: Oral microbiota can contribute to dental problems such as cavities and gum disease. For example:- Harmful bacteria in the mouth can interact with sugars and produce acids that damage tooth enamel.