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Lesson 4.pptx

  1. Ecology of microorganisms in the oral cavity. Normal microflora of the body and oral cavity and its age features.
  2. Microbes appear in every corner of human life, and microbes affect every aspect of human life. The human oral cavity contains a number of different habitats. Synergy and interaction of variable oral microorganisms help human body against invasion of undesirable stimulation outside. However, imbalance of microbial flora contributes to oral diseases and systemic diseases. Oral microbiomes play an important role in the human microbial community and human health.
  3. The oral cavity is a border area between the environment and the human organism, a gateway for food, an outpost of the immune system and above all a multilayered habitat inhabited by countless microorganisms. The mouth is continually exposed to organisms from the external environment ,beginning with the passage through the birth canal. In time a ecological balance is reached that serves to establish a resident microbial flora that remains fairly stable throughout life. Microorganisms in mouth were first described by Anton von Leeuwenhoek in 1683.
  4. HISTORY Louis Pasteur – Father of Microbiology Antony Van Leeuwenhook in 16th century identified bacteria and its shapes – rods , cocci and spiral forms . Willoughby D. Miller proposed that carbohydrate from food were broken down by oral bacteria and the resulting acids caused dissolution of the enamel . Pierre Fauchard in 1745 described tartar and plaque . J.K. Clark in 1942 identified coccus from carious lesion and named as Streptococcus mutans
  5. The discovery of microbes dates back to the 1700 y. Historically, Antonie van Leeuwenhoek peered and examined dental plaque sampled from himself and others through his microscope. His sense of awe and his early appreciation of the diversity our microbial partners were evident. He named the microbes “Dierken”, meaning small lively objects. The human oral cavity contains a number of different habitats, including the teeth, gingival sulcus, tongue, hard and soft palates, and tonsils, and acts the tube which connect the outside and the digestive tract and respiratory tract of human body, which provides the appropriate space for the colonization of microorganisms. The microorganisms found in the human oral cavity have been referred to as the oral microflora, oral microbiota, or oral microbiome.
  6. Ecology • Ecology (from Greek) is the scientific study of interactions among organisms and their environment, such as the interactions organisms have with each other and with their abiotic environment; The ecosystem is composed of microbial communities living on specific sites surrounded by a different physical and chemical elements.
  7. Ecosystems • Ecosystems are composed of dynamically interacting parts including organisms, the communities they make up, and the non-living components of their environment; Ecosystem processes, such as primary production, nutrient cycling, and various niche construction activities, regulate the flux of energy and matter through an environment.
  8. Microflora •Living microorganisms that are so small that they can be seen only with a microscope and that maintain a more or less constant presence in a particular area; •Includes bacteria, viruses, protozoa, fungi.
  9. Oral microflora • Oral microflora refers to the community of microorganisms coexisting in the oral cavity as its primary habitat; • These strains of bacteria colonize the various different surfaces present in the oral cavity, and communicate between each other through complex cell signaling processes; • The body’s own defenses also play a role in maintaining a balance and ensuring a healthy oral environment.
  10. Normal - resident flora In a healthy body, the internal tissues - blood, brain, muscle, etc., are normally free of microorganisms; However, the surface tissues - skin and mucous membranes, are constantly in contact with environmental organisms and become readily colonized by various microbial species; The mixture of organisms regularly found at any anatomical site is referred to as the normal flora or resident flora, some researchers prefer the term "indigenous microbiota".
  11. Resident microflora Typical microflora of a econiche; Microorganisms are separated and grouped according to the different conditions of life; Resident microflora has an important function in host: Digestive and nutritional; Competition with pathogenic microflora.
  12. Transient Microbiota Transient microbes are just passing through; Although they may attempt to colonize the same areas of the body as do resident microbiota, transients are unable to remain in the body for extended periods of time due to: Competition from resident microbes; Elimination by the body’s immune system; Physical or chemical changes within the body that discourage the growth of transient microbes.
  13. Opportunistic microbes Under normal conditions, resident and transient microbes cause the host no harm; However, if the opportunity arises, some of these microbes are able to cause disease and become opportunistic pathogens. This can happen due to a number of different conditions: When the immune system isn’t working properly, normal flora can overpopulate or move into areas of the body where they do not normally occur; When the balance of normal microbes is disrupted, for example when a person takes broad spectrum antibiotics, microbes that are normally crowded out by resident microbes have an opportunity to take over; Disease can result when normal flora are traumatically introduced to an area of the body that they do not normally occur in.
  14. Endogenous microflora That is microflora already present in the body, but has previously been inapparent or dormant. Bacterial flora is endogenous bacteria, which is defined as bacteria that naturally reside in a closed system.
  15. Exogenous microflora Exogenous bacteria are microorganisms introduced to closed biological systems from the external world; They exist in aquatic and terrestrial environments, as well as the atmosphere; Microorganisms in the external environment have existed on Earth for 3.5 billion years; Exogenous bacteria can be either benign or pathogenic.
  16. The origin of Oral Microflora The microflora present in our mouths is acquired from birth, as newborn babies have no bacteria in their mouths; Over time, the oral cavity becomes colonized by the strains of bacteria that eventually form the resident microflora, which establish a permanent population in the mouth; Over time as the individual is further exposed to external sources of bacteria, the biodiversity of the oral cavity increases, to a point where stability is reached. This is termed the climax community.
  17. The source of microorganisms • The source of these microorganisms mainly comes from saliva, although it also includes the food and water consumed by the individual; • This process takes place within the first few hours of life; • Majority of children obtain their resident microflora from their mothers, as they often possess identical strains of bacteria; • This is known as vertical transmission; • Horizontal transmission also takes place as children interact with their peers, and later in life between spouses and partners. • Streptococcus salivarius is dominant and may make up 98% of the total oral flora until the appearance of the teeth (6 - 9 months in humans).
  18. Periods of formation of the oral ecosystem The neonatal period: Mostly aerobes; Candida albicans - 54%; Obtained from the mother and the surrounding area; Period before eruption: Facultative anaerobes and anaerobes; Streptococcus - 90%; Actinomyces; Candida albicans. After eruption The eruption of the teeth during the first year leads to colonization by S. mutans and S. sanguis; These bacteria require a nondesquamating (nonepithelial) surface in order to colonize; They will persist as long as teeth remain; Other strains of streptococci adhere strongly to the gums and cheeks but not to the teeth.
  19. Variations in Microflora Everyone has microflora, but it varies between people depending on the condition of their oral cavity; Not all individuals would have the same microflora profile; Not all bacteria are ubiquitous in all individuals.
  20. DEFINITIONS: • Commensal: An organism living in/on an organism of another species without injuring the host; • Parasite: An organism living in/on and at the expense of another organism (the host). Equivalent to a pathogen; • Opportunistic Pathogen: A commensal organism that can cause disease in certain circumstances ; • Symbiosis: The mutually beneficial association between two organisms ; • Aerobic Organism: requiring oxygen for growth and replication; • Anaerobe: Organism that grows and replicates in the absence of oxygen; not necessarily killed by oxygen; • Strict anaerobe: Anaerobe killed by oxygen; • Facultative anaerobe: Organism capable of growth and replication in the presence or absence of oxygen;
  21. Important Oral Bacteria Gram Positive organisms: • Rods (bacilli), cocci or irregular shape (pleomorphic); • Oxygen tolerance varies from aerobes to strict anaerobes; • Most are fermentative; • Cell wall has thick peptidoglycan layer (penicillin has effect by interfering production of this layer). Streptococci: Isolated from all sights of the mouth; Large proportion of resident microflora; Majority α-haemolytic.
  22. Strep mutans: Associated with caries; Associated with bacterial endocarditis. Streptococcus mutans. Streptococcus mutans is the primary bacterium involved in plaque formation and initiation of dental caries; Viewed as an opportunistic infection, dental disease is one of the most prevalent and costly infectious diseases Strep salivarius: Colonise mucosal surfaces especially the tongue. Strep angiosus: Isolated dental plaque & mucosal surfaces; Seen in maxillofacial infections, brain, liver etc.
  23. Actinomyces, facultative anaerobe; • Lactobacillus, produce lactic acid, facultative anaerobe, role in dentine caries rather than enamel caries; • Streptococcus facultative anaerobic cocci, produce lactic acid some implicated in caries. Lactobacillus species Lactobacilli in the oral cavity probably contribute to acid formation that leads to dental caries.
  24. Biofilm formation Biofilms usually occur when one bacterial species attaches specifically or non specifically to a surface, and then secretes carbohydrate slime (exopolymer) that imbeds the bacteria and attracts other microbes to the biofilm for protection or nutritional advantages. Biofilm The classic biofilm that involves components of the normal flora of the oral cavity is the formation of dental plaque on the teeth; Plaque is a naturally-constructed biofilm, in which the consortia of bacteria may reach a thickness of cells on the surfaces of the teeth; These accumulations subject the teeth and gingival tissues to high concentrations of bacterial metabolites, which result in dental disease.
  25. Factors Affecting Growth of Microorganisms in the oral cavity • 1. Temperature; • 2. REDOX Potential / Anaerobiosis; • 3. pH; • 4. Nutrients (endogenous & exogenous (diet); • 5. Host Defences (Innate & Acquired immunity); • 6. Host genetics (changes in immune response etc); • 7. Antimicrobial agents & inhibitors.
  26. Oral flora changes with age. Time during a lifetime MAJOR COMPONENTS & CHANGES IN ORAL FLORA Newborn Oral cavity sterile. Soon colonised by facultative and aerobic organisms; esp S. salivarius 6 months Flora becomes more complex & includes anaerobic orgs eg. Veillonella sp. & Fusobacteria Tooth eruption Increase in complexity. S sanguis, S mutans and A viscosus appear. New habitats include hard surfaces and gingival crevice. Child to adult Various anaerobes frequently found inc. Members of the Bacteroidaceae. Spirochaetes isolated more frequently Loss of teeth Disappearance of S mutan, S sanguis, spirochaetes and many anaerobes Dentures etc Reappearance of bacteria able to grow on hard surfaces.
  27. Regulation of oral microbiota on systematic diseases •Oral microbiota is related to oral and systematic diseases. Oral microbiota is altered during oral and whole body diseases. Thus, oral microbiota will be a new target for treating oral diseases and improving the body’s physical state.
  28. Thank you