scoresvideos
Microbiology
Table of Contents
Unit 24 Overview: Digestive System Infections
24.1 Anatomy and Normal Microbiota of the Digestive System
24.2 Microbial Diseases of the Mouth and Oral Cavity
24.3 Bacterial Infections of the Gastrointestinal Tract
24.4 Viral Infections of the Gastrointestinal Tract
24.5 Protozoan Infections of the Gastrointestinal Tract
24.6 Helminthic Infections of the Gastrointestinal Tract

🦠microbiology review

24.2 Microbial Diseases of the Mouth and Oral Cavity

Citation:

The mouth is a microbial hotspot, home to diverse bacteria that can cause tooth decay and gum disease. Streptococcus mutans and Lactobacillus species produce acid that erodes enamel, while Porphyromonas gingivalis and others trigger inflammation in gums and bone.

Preventing oral diseases involves good hygiene, regular dental visits, and limiting sugary foods. When problems arise, treatments range from fillings for cavities to scaling for gum disease. Understanding these microbes and their interactions helps maintain a healthy oral ecosystem.

Microbial Diseases of the Mouth and Oral Cavity

Causes and progression of dental diseases

  • Dental caries (tooth decay)
    • Caused by acid-producing bacteria, primarily Streptococcus mutans and Lactobacillus species
    • Bacteria metabolize dietary sugars (sucrose, fructose) and produce acid as a byproduct
    • Acid demineralizes tooth enamel, leading to the formation of cavities
    • Progression of dental caries:
      1. Initial demineralization of tooth enamel
      2. Enamel decay and formation of small cavities
      3. Dentin decay as bacteria penetrate deeper into the tooth
      4. Pulp infection if decay reaches the inner core of the tooth
  • Periodontal disease
    • Inflammation and infection of the gums (gingivae) and supporting structures of the teeth (periodontal ligament, alveolar bone)
    • Caused by the buildup of dental plaque, a biofilm containing bacteria
    • Key pathogens involved in periodontal disease: Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola
    • Progression of periodontal disease:
      1. Gingivitis - inflammation of the gums without bone loss
      2. Periodontitis - gum recession, destruction of periodontal ligament, and alveolar bone loss
      3. Advanced periodontitis - severe bone loss and tooth mobility, leading to tooth loss

Key oral pathogens and infections

  • Streptococcus mutans
    • Primary cause of dental caries
    • Produces extracellular polysaccharides (glucans) that help bacteria adhere to tooth surfaces and form dental plaque
    • Ferments sugars to produce lactic acid, which demineralizes tooth enamel
  • Lactobacillus species
    • Secondary colonizers in dental caries
    • Thrive in acidic environments created by S. mutans and contribute to tooth decay progression
    • Produce additional acids that further demineralize tooth structure
  • Porphyromonas gingivalis
    • Keystone pathogen in periodontal disease
    • Produces virulence factors (gingipains, lipopolysaccharide) that trigger inflammation and tissue destruction
    • Modulates host immune response, enabling persistent infection and chronic inflammation
  • Tannerella forsythia and Treponema denticola
    • Work synergistically with P. gingivalis to cause periodontal disease
    • Produce enzymes (proteases) that break down connective tissue and contribute to bone loss
    • Form a "red complex" with P. gingivalis, associated with severe periodontal disease
  • Candida albicans
    • Fungal pathogen that causes oral thrush (oropharyngeal candidiasis)
    • Overgrowth can occur due to immunosuppression (HIV/AIDS), antibiotic use, or denture wear
    • Forms white, curd-like patches on the tongue, palate, and buccal mucosa

Oral microbiome and host interactions

  • Oral microbiome
    • Diverse community of microorganisms living in the oral cavity
    • Includes bacteria, fungi, viruses, and protozoa
    • Plays a crucial role in maintaining oral health and preventing disease
  • Biofilm formation
    • Process by which microorganisms adhere to surfaces and form structured communities
    • Dental plaque is a prime example of a biofilm in the oral cavity
    • Contributes to the development of dental caries and periodontal disease
  • Dental anatomy
    • Structure of teeth and surrounding tissues influences microbial colonization
    • Enamel, dentin, and cementum provide different surfaces for bacterial attachment
  • Saliva composition
    • Contains antimicrobial compounds that help regulate the oral microbiome
    • Buffers pH to protect against acid-induced tooth demineralization
  • Host immune response
    • Innate and adaptive immune mechanisms in the oral cavity help control microbial populations
    • Dysregulation of immune responses can contribute to periodontal disease progression

Prevention and treatment of oral diseases

  • Prevention strategies for dental caries and periodontal disease
    • Proper oral hygiene practices
      • Brushing teeth twice daily with fluoride toothpaste
      • Flossing daily to remove plaque between teeth
      • Using antiseptic mouthwash to reduce bacterial load
    • Regular dental check-ups and professional cleaning (scaling and polishing)
    • Limiting consumption of sugary and acidic foods and drinks (soda, candy)
    • Fluoride treatments to strengthen tooth enamel and prevent demineralization
    • Dental sealants to prevent bacteria from colonizing pits and fissures on tooth surfaces
  • Treatment strategies for specific oral diseases
    • Dental caries treatment
      • Removal of decayed material and filling of cavities with restorative materials (composite resin, amalgam)
      • Root canal therapy for advanced cases involving pulp infection to prevent tooth loss
    • Periodontal disease treatment
      • Scaling and root planing to remove plaque, tartar (calculus), and bacterial toxins from tooth surfaces and periodontal pockets
      • Antibiotics (metronidazole, doxycycline) to control bacterial infection and reduce inflammation
      • Surgical interventions for advanced cases, such as flap surgery to reduce pocket depth and bone grafts to regenerate lost bone
    • Oral thrush treatment
      • Antifungal medications, such as nystatin oral suspension or fluconazole tablets
      • Improving oral hygiene, disinfecting dentures, and treating underlying conditions that promote fungal overgrowth
    • Consideration of antimicrobial resistance when selecting treatments for oral infections

Key Terms to Review (88)

β-lactams: β-lactams are a class of broad-spectrum antibiotics that contain a β-lactam ring in their molecular structure. They work by inhibiting the synthesis of bacterial cell walls, leading to cell death.
Abscesses: Abscesses are localized collections of pus caused by bacterial infections. In the mouth and oral cavity, they can form due to tooth decay, gum disease, or injury.
Abscess: An abscess is a confined pocket of pus that collects in tissues, organs, or spaces inside the body, usually caused by a bacterial infection. It forms as a defensive reaction of tissue to prevent the spread of infectious materials to other parts of the body.
Acute herpes labialis: Acute herpes labialis is a viral infection caused by the herpes simplex virus type 1 (HSV-1), resulting in cold sores or fever blisters primarily around the mouth. It is highly contagious and typically reactivates during periods of stress or immunosuppression.
Acute necrotizing ulcerative gingivitis: Acute necrotizing ulcerative gingivitis (ANUG) is a severe infection of the gums characterized by rapid onset, pain, and the presence of ulcers. It is often associated with poor oral hygiene and stress.
Amoxicillin clavulanate: Amoxicillin clavulanate is a combination antibiotic consisting of amoxicillin and clavulanic acid. It's used to treat various bacterial infections, including those in the mouth and oral cavity.
Atherosclerosis: Atherosclerosis is a condition where the arteries become narrowed and hardened due to a buildup of plaque around the artery wall. It can lead to serious health issues like heart attack, stroke, and other cardiovascular diseases.
Biofilm: A biofilm is a complex aggregation of microorganisms growing on a surface, encased in a self-produced matrix of extracellular polymeric substances (EPS). These communities are highly resistant to antimicrobial agents and can be found in various environments, including medical devices and human tissues.
Caries: Caries are the decay and destruction of tooth enamel caused by bacterial activity, often leading to cavities. They are primarily associated with an imbalance in oral microbiota and dietary sugars.
Cementum: Cementum is a specialized calcified substance covering the root of a tooth. It helps anchor the periodontal ligament fibers to the tooth, playing a critical role in maintaining dental stability.
Cavities: Cavities, also known as dental caries, are permanently damaged areas in the hard surface of your teeth that develop into tiny openings or holes. They are caused by a combination of factors including bacteria in your mouth, frequent snacking, sipping sugary drinks, and inadequate cleaning of teeth.
Cold sores: Cold sores are painful blisters that appear on the lips and around the mouth, caused by the herpes simplex virus (HSV-1). They are highly contagious and can be triggered by various factors, including stress and immune suppression.
Crown: The crown is the visible part of a tooth above the gum line, covered by enamel. It plays a crucial role in chewing and breaking down food during digestion.
Defensins: Defensins are small, antimicrobial peptides produced by various cells, including epithelial cells and neutrophils. They play a crucial role in the innate immune system by disrupting the membranes of pathogens.
Dental calculus: Dental calculus, also known as tartar, is hardened dental plaque that forms on teeth due to the accumulation of minerals from saliva. It provides a surface for further bacterial colonization and can lead to periodontal disease.
Dentin: Dentin is the calcified tissue beneath the enamel of a tooth, providing structural support and protection to the pulp. It contains microscopic tubules that can transmit sensations and nutrients.
Dental caries: Dental caries, commonly known as cavities, are the result of tooth decay caused primarily by bacterial action on fermentable carbohydrates. These bacteria metabolize sugars to produce acids that demineralize the tooth enamel and dentin.
Dextran: Dextran is a complex branched polysaccharide composed of multiple glucose molecules. It is produced by certain bacteria and plays a key role in dental plaque formation.
Endocarditis: Endocarditis is an infection of the inner lining of the heart chambers and valves. It is often caused by bacteria entering the bloodstream and attaching to damaged areas of the heart.
Enamel: Enamel is the hard, outermost layer of a tooth that protects it from physical and chemical damage. It is the hardest substance in the human body and primarily composed of hydroxyapatite, a crystalline calcium phosphate.
Encephalitis: Encephalitis is the inflammation of the brain, typically caused by viral infections. It can result in symptoms ranging from mild flu-like signs to severe neurological damage.
Eucalyptol: Eucalyptol is a natural organic compound commonly found in eucalyptus oil. It possesses antimicrobial properties, making it useful in controlling microbial growth and treating oral infections.
Famciclovir: Famciclovir is an antiviral medication used to treat herpes virus infections, including shingles and genital herpes. It works by inhibiting viral DNA replication.
Fluoride: Fluoride is a naturally occurring mineral that helps prevent dental cavities by inhibiting the demineralization of enamel and promoting its remineralization. It also possesses antimicrobial properties, making it effective in controlling oral bacteria.
Fructose: Fructose is a simple sugar (monosaccharide) found in many plants and is one of the three dietary monosaccharides, along with glucose and galactose. It is commonly found in fruits, honey, and root vegetables.
Gingival space: The gingival space is the area between the teeth and the surrounding gum tissue. This space can harbor bacteria and contribute to oral infections.
Gingivitis: Gingivitis is inflammation of the gums caused by bacterial infection, leading to redness, swelling, and potential bleeding. It is often a result of poor oral hygiene that allows plaque to accumulate on teeth.
Glucose: Glucose is a simple sugar and an essential energy source for cells. It is a primary product of photosynthesis and a key player in cellular respiration.
Herpetic gingivostomatitis: Herpetic gingivostomatitis is an oral infection caused by the herpes simplex virus, typically HSV-1. It leads to inflammation of the gums and mucous membranes in the mouth.
Lactic acid: Lactic acid is an organic acid produced by certain bacteria through fermentation. It plays a role in maintaining the pH balance in various parts of the body, including the urogenital and digestive systems.
Lipopolysaccharide: Lipopolysaccharide (LPS) is a major component of the outer membrane of Gram-negative bacteria. It acts as an endotoxin and can trigger strong immune responses in humans.
Lipoteichoic acids: Lipoteichoic acids are teichoic acids linked to a lipid and found in the cell walls of Gram-positive bacteria. They play a role in bacterial adhesion and immune system evasion.
Meningitis: Meningitis is an inflammation of the protective membranes covering the brain and spinal cord, known as the meninges. It can be caused by bacterial, viral, fungal, or parasitic infections.
Methanobrevibacter: Methanobrevibacter is a genus of archaea known for producing methane as a metabolic byproduct. It is commonly found in the human oral cavity and gastrointestinal tract.
Mumps: Mumps is a contagious viral infection characterized by the swelling of the parotid glands, which are salivary glands located near the ears. It can also cause complications in other parts of the body, including the nervous system and reproductive organs.
Nystatin: Nystatin is an antifungal antibiotic used to treat fungal infections, particularly those caused by Candida species. It works by binding to ergosterol in the fungal cell membrane, creating pores that lead to cell death.
Oral thrush: Oral thrush is a fungal infection in the mouth caused by the overgrowth of Candida species, most commonly Candida albicans. It manifests as white lesions on the tongue and inner cheeks, sometimes leading to discomfort and difficulty swallowing.
Oral herpes: Oral herpes is a viral infection caused by the herpes simplex virus type 1 (HSV-1) that typically manifests as cold sores or fever blisters around the mouth and lips. It is highly contagious and can spread through direct contact with infected saliva or lesions.
Paramyxovirus: Paramyxovirus is a family of viruses known to cause diseases in humans and animals. These viruses are associated with respiratory infections but can also impact other systems, including the oral cavity.
Periodontal disease: Periodontal disease is a serious gum infection that damages the soft tissue and destroys the bone that supports your teeth. It is primarily caused by bacteria in dental plaque.
Periodontitis: Periodontitis is a serious gum infection that damages the soft tissue and destroys the bone supporting your teeth. It is caused by bacterial accumulation and can lead to tooth loss if untreated.
Plaque: Plaque is a sticky, colorless film of bacteria and sugars that constantly forms on our teeth. It is the primary cause of cavities and gum disease.
Proteases: Proteases are enzymes that break down proteins by hydrolyzing peptide bonds. They play crucial roles in various biological processes, including infection and pathogenicity.
Pulp: Pulp is the soft tissue found in the center of a tooth, containing nerves, blood vessels, and connective tissue. It plays a crucial role in the formation and nourishment of the dentin.
Root canal: A root canal is a dental procedure used to treat infection at the center of a tooth (the pulp) and involves removing the infected tissue to prevent further damage. It is crucial for saving a tooth that would otherwise need to be extracted.
Saliva: Saliva is a clear, watery fluid produced by salivary glands in the mouth. It contains enzymes, antibodies, and other substances that aid in digestion and provide immune defense.
Salivary glands: Salivary glands are exocrine glands located in and around the mouth that produce saliva, which aids in digestion and maintains oral health. They include the parotid, submandibular, and sublingual glands.
Streptococcus mutans: Streptococcus mutans is a Gram-positive bacterium primarily found in the human oral cavity. It plays a significant role in the development of dental caries (tooth decay).
Streptococcus: Streptococcus is a genus of Gram-positive bacteria that often occur in chains or pairs. They are known for causing a variety of infections in humans, ranging from mild throat infections to life-threatening diseases.
Sucrose: Sucrose is a disaccharide composed of glucose and fructose. It is commonly known as table sugar and plays a key role in microbial metabolism and oral health.
Tartar: Tartar, also known as dental calculus, is a hardened form of plaque that develops on teeth and below the gumline. It provides a surface for further plaque accumulation and can lead to periodontal disease.
Teeth: Teeth are hard, calcified structures in the mouth that play a crucial role in mechanical digestion by breaking down food into smaller pieces. They also serve as surfaces for biofilm formation and can be affected by various microbial diseases.
Tetracycline: Tetracycline is a broad-spectrum antibiotic used to treat a wide variety of bacterial infections. It works by inhibiting protein synthesis in bacteria, preventing them from growing and multiplying.
Thymol: Thymol is a natural monoterpenoid phenol derived from thyme oil, exhibiting strong antimicrobial properties. It is widely used in mouthwashes and hand sanitizers for its ability to control microbial growth.
Trench mouth: Trench mouth, also known as acute necrotizing ulcerative gingivitis (ANUG), is a severe gum infection characterized by the rapid onset of pain, bleeding, and ulceration of the gums. It is commonly associated with poor oral hygiene, stress, smoking, and malnutrition.
Zinc chloride: Zinc chloride is a chemical compound often used as a disinfectant and antiseptic. It is effective in controlling microbial growth through its denaturing properties.
Xylitol: Xylitol is a naturally occurring sugar alcohol used as a sugar substitute. It is known for its dental health benefits, particularly in reducing the risk of cavities and tooth decay.
Biofilm Formation: Biofilm formation is the process by which microorganisms, such as bacteria and fungi, adhere to surfaces and develop into complex, structured communities encased in a self-produced extracellular matrix. This phenomenon is closely linked to the pathogenesis and persistence of various microbial infections, as well as the effectiveness of antimicrobial agents and disinfectants.
Antimicrobial Resistance: Antimicrobial resistance refers to the ability of microorganisms, such as bacteria, viruses, and fungi, to resist the effects of antimicrobial drugs, including antibiotics, antivirals, and antifungals. This phenomenon is a growing global public health concern as it can lead to the failure of standard treatments, increased healthcare costs, and the spread of infections.
Defensins: Defensins are a class of antimicrobial peptides that serve as part of the innate immune system's chemical defenses against pathogens. They are found in various tissues and bodily fluids, playing crucial roles in pathogen recognition, phagocytosis, and protecting the integrity of the skin, eyes, respiratory tract, and oral cavity.
Host Immune Response: The host immune response refers to the complex system of biological mechanisms and processes by which the human body recognizes and defends itself against harmful pathogens, such as bacteria, viruses, fungi, and parasites. This response is crucial in maintaining health and preventing the development of infectious diseases.
Dental Caries: Dental caries, also known as tooth decay, is a bacterial infectious disease that causes permanent damage to the hard surface of a tooth. It is one of the most common health problems affecting people of all ages worldwide and is a major concern in the context of microbial diseases of the mouth and oral cavity.
Oral Biofilm: An oral biofilm is a complex, structured, and dynamic microbial community that adheres to the surfaces within the oral cavity, including teeth, gums, and other oral tissues. These biofilms are formed by the attachment and growth of various bacterial species, along with other microorganisms, within a self-produced extracellular matrix.
Periodontitis: Periodontitis is a severe form of gum disease that can lead to the destruction of the tissues supporting the teeth, including the gums, periodontal ligament, and alveolar bone. It is a chronic inflammatory condition caused by the buildup of harmful bacteria in the mouth and is a major cause of tooth loss in adults.
Halitosis: Halitosis, also known as bad breath, is a condition characterized by an unpleasant odor emanating from the mouth. It is a common problem that can have various underlying causes related to the microbial diseases of the mouth and oral cavity.
Porphyromonas gingivalis: Porphyromonas gingivalis is an anaerobic, Gram-negative bacterium that is strongly associated with the development and progression of periodontal disease, a common and serious infection of the gums. As a key pathogen in the oral microbiome, P. gingivalis plays a central role in the microbial diseases of the mouth and oral cavity.
Gingiva: The gingiva, or gums, are the soft tissues that surround and support the teeth. They are an integral part of the oral cavity and play a crucial role in the overall health and function of the mouth.
Gingivitis: Gingivitis is a common and mild form of gum disease that causes inflammation of the gingiva, the part of the gum around the base of the teeth. It is typically caused by a buildup of plaque, a sticky film of bacteria that forms on the teeth.
Periodontal Ligament: The periodontal ligament is a specialized connective tissue that attaches the tooth to the alveolar bone within the oral cavity. It plays a crucial role in the overall health and function of the teeth and surrounding structures.
Dental Plaque: Dental plaque is a sticky, colorless film of bacteria that constantly forms on the surface of teeth. It is a key factor in the development of various microbial diseases of the mouth and oral cavity.
Dental Scaling: Dental scaling is a professional dental cleaning procedure that involves the removal of plaque, calculus (tartar), and stains from the surfaces of teeth, particularly in the areas below the gumline. This process helps maintain oral hygiene and prevent the development of various microbial diseases affecting the mouth and oral cavity.
Oral Microbiome: The oral microbiome refers to the diverse community of microorganisms, including bacteria, archaea, fungi, and viruses, that naturally reside in the human oral cavity. This complex ecosystem plays a crucial role in maintaining oral and overall health.
Periodontal Probing: Periodontal probing is a diagnostic technique used in dentistry to assess the health and condition of the gums and supporting structures around the teeth. It involves the gentle insertion of a calibrated probe into the space between the tooth and the gum, known as the periodontal pocket, to measure its depth and detect any signs of inflammation or disease.
Glucans: Glucans are a class of polysaccharides composed of glucose monomers linked together in a variety of configurations. They are found in the cell walls of many microorganisms, including bacteria and fungi, and play important roles in microbial diseases of the mouth and oral cavity.
Oral Thrush: Oral thrush is a fungal infection that occurs in the mouth, caused by an overgrowth of the yeast Candida albicans. It is a common condition, particularly in individuals with weakened immune systems or those taking certain medications.
Salivary Diagnostics: Salivary diagnostics refers to the use of saliva as a diagnostic tool to detect and monitor various health conditions and diseases. It involves analyzing the composition and properties of saliva to obtain valuable information about an individual's overall health status.
Treponema denticola: Treponema denticola is a spiral-shaped, motile, anaerobic bacterium that is a common inhabitant of the human oral cavity and is associated with the development of periodontal diseases, particularly chronic periodontitis.
Oral Hygiene Practices: Oral hygiene practices refer to the routine activities and habits individuals engage in to maintain the health and cleanliness of their mouth, teeth, and gums. These practices are crucial in preventing the development and progression of microbial diseases that can affect the oral cavity.
Salivary Immunoglobulin A: Salivary immunoglobulin A (sIgA) is a type of antibody found in saliva and other mucosal secretions that plays a crucial role in the immune defense of the oral cavity, providing protection against microbial pathogens and maintaining a healthy oral microbiome.
Gingipains: Gingipains are a group of cysteine proteases produced by the anaerobic bacterium Porphyromonas gingivalis, a key pathogen associated with chronic periodontal disease. These proteolytic enzymes play a crucial role in the virulence and pathogenesis of P. gingivalis, contributing to the development and progression of various microbial diseases of the mouth and oral cavity.
Root Planing: Root planing is a dental procedure that involves the careful removal of the outermost layer of the tooth root to smooth its surface. This process is typically performed as part of the treatment for periodontal (gum) diseases, such as gingivitis and periodontitis, which are microbial diseases of the mouth and oral cavity.
Oropharyngeal Candidiasis: Oropharyngeal candidiasis, also known as thrush, is a fungal infection that occurs in the mouth and throat. It is caused by the overgrowth of a type of yeast called Candida, which is normally present in the oral cavity but can proliferate and cause disease under certain conditions.
Dental Anatomy: Dental anatomy refers to the structure and composition of the teeth, gums, and supporting structures within the oral cavity. It encompasses the various components that make up the human dentition and their functions in the overall health and functioning of the mouth and oral system.
Tannerella forsythia: Tannerella forsythia is an anaerobic, Gram-negative bacterium that is a key member of the oral microbiome and a major contributor to the development of periodontal disease. It is closely associated with the microbial dysbiosis that leads to chronic inflammation and destruction of the gums and supporting structures of the teeth.
Saliva Composition: Saliva composition refers to the complex mixture of substances found in the saliva produced by the salivary glands. This saliva plays a crucial role in maintaining oral health and contributing to the microbial environment within the mouth and oral cavity.
Coaggregation: Coaggregation is the process by which different microbial species or strains adhere to one another, forming complex multi-species communities within the oral cavity. This phenomenon is a crucial aspect of microbial diseases affecting the mouth and oral region.
Leukotoxin: Leukotoxin is a bacterial exotoxin that specifically targets and damages leukocytes, also known as white blood cells, which are critical components of the human immune system. This toxin is produced by certain pathogenic bacteria and plays a significant role in the development of microbial diseases affecting the mouth and oral cavity.
Quorum Sensing: Quorum sensing is a communication mechanism used by bacteria to coordinate gene expression and behavior in response to changes in cell population density. It allows bacteria to sense and respond to the presence of other bacteria, enabling them to act in a coordinated manner as a community rather than as individual cells.