Oral microbial flora

Oral health is inextricably linked to general health, and vice versa.

The mouth is the gateway of the body to the external world and represents one of the most biologically complex sites in the body.

1. ORAL MICROBIAL FLORA PRESENTED BY- DR. AISHWARYA ARYA DR. APEKSHA RAINA FIRST YEAR PG

2. CONTENTS INTRODUCTION HUMAN MICROBIOTA MICROBIAL COLONISATION BENEFITS OF MICROBIOTA HOMEOSTASIS ORAL ECOSYSTEM INTRODUCTION TO ORAL MICROBIAL FLORA MOUTH AS A AMICROBIAL HABITAT FACTORS AFFECTING GROWTH OF MICRO ORGANISMS RESIDENT ORAL MICROBIOTA ACQUISITION OF MICRO ORGANISMS METABOLISM OF MICRO ORGANISMS BENEFITIS OF MICRO ORGANISMS COVID -19 INTRODUCTION TO IMPORTANT MICRO ORGANISMS CONCLUSION REFERENCES 2

3. INTRODUCTION Oral health is inextricably linked to general health, and vice versa. The mouth is the gateway of the body to the external world and represents one of the most biologically complex sites in the body. The mouth can provide healthcare workers with a ‘window’ into a person’s oral and general health . Maintaining a healthy mouth is therefore of vital importance for a person’s self esteem and general health. Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. 3

4. HUMAN MICROBIOME AN MICROBIOTA Joshua Lederberg “ T o signify the ecological community of commensal, symbiotic, and pathogenic microorganisms that literally share our body space and have been all but ignored as determinants of health and disease” The microbiota is the term used to define the full complement of microorganisms at a particular location. The microbiome, which describes the microbiota and its collective genetic material at a site on the human body, or elsewhere. Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. 4

5. MICROBIAL COLONISATION The microbial colonisation of all environmentally accessible surfaces of the body begins at birth. Differences in physical and biological properties, each surface is suitable for colonisation by only a proportion of these microbes. This results in the acquisition, selection and natural development of a diverse but characteristic microbiota at distinct sites . Those that are expected to be present, and that under normal circumstances do not cause disease, but instead participate in maintaining health, are deemed members of the normal flora. Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. 5

6. BENEFITS OF THE HUMAN MICROBIOTA Aid the digestion of otherwise indigestible dietary compounds Synthesise beneficial compounds , such as B vitamins (folic acid, biotin) and vitamin K Metabolise potentially harmful compounds such as bile acids, cholesterol, nitrosamines, etc Generate short chain fatty acids from the metabolism of dietary polysaccharides which act as key energy sources for the human colonic mucosa Prevent colonisation by exogenous microorganisms ( colonisation resistance) Promote the development of a competent immune system , and modulate proinflammatory pathways Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. 6

7. Microbial interactions include negative interactions (− feedbacks), and positive interactions (+ feedbacks) Positive interactions likely increase the productivity of the community but potentially destabilize the community while negative interactions often reduce cooperative activities but favor species diversity and community stability. These interactions form complex networks that finally balance the homeostasis of the community. HOMEOSTASIS 7

8. DYSBIOSIS Major changes to the biology of the mouth from exogenous sources (examples include: antibiotic treatment or the frequent intake of fermentable carbohydrates in the diet) From endogenous changes such as alterations in the integrity of host defences following drug therapy, which perturb the natural stability of the microbiota Failure of oral hygiene practices to maintain the oral microbiota at levels compatible with health The colonisation of sites not normally accessible to oral microorganisms; A shift in this balance can Lead to a deleterious relationship developing; this process is termed dysbiosis

9. ORAL MICROBIAL FLORA The properties of the mouth as a microbial habitat are dynamic and will change over the life of an individual. During the first few months of life , the mouth provides only mucosal surfaces for microbial colonisation . The eruption of teeth provides a unique, hard nonshedding surface which enables much larger masses of microorganisms (dental plaque) to accumulate as biofilms. In addition, gingival crevicular fluid (GCF ) is produced that can provide additional nutrients permitting the growth of the fastidious microorganisms found subgingivally . The mouth, being an extension of an external body site, has a natural microflora . 9

10. TERMINOLOGIES The commensal flora which survive in the mouth only for short periods are referred as transient flora. The resident flora include the complete collection of microorganisms that are regularly isolated from a site That species found characteristically in a particular habitat should be termed autochthonous microorganisms . These multiply and persist at a site. Allochthonous organisms which originate from elsewhere and are generally unable to colonise successfully unless the ecosystem is severely perturbed. 10

11. Microbial acquisition depends on the transmission of microorganisms to the site of potential colonisation . Initially, in the mouth, this is by passive inoculation mainly from the mother, but also from other individuals in close proximity to the baby and from ingested milk and water. The mode of delivery of the baby influences the microbiota of the newborn. Conventionally delivered babies harbour bacterial communities that are similar to the vaginal microbial community of the mother which include representatives of genera like Lactobacillus, Prevotella and Atopobium . In contrast, babies delivered by Caesarean section have bacterial communities that resemble the skin microbiota , and include many Staphylococcus species ACQUISITION OF NORMAL ORAL FLORA Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. 11

12. The oral microbiota of breastfed babies differs from that of formulafed infants during the first months of life. Lactobacilli (especially L. plantarum) are more common in breastfed infants , and this may influence the subsequent development of the infant oral microbiota. As these organisms have been shown to inhibit the growth of mutans streptococci and Candida albicans. ACQUISITION OF NORMAL ORAL FLORA Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. 12

13. ACQUISITION OF NORMAL ORAL FLORA Infant mouth is usually sterile at birth, few organisms are acquired from mothers birth canal. The colonisation of the oral cavity starts about the time of birth .(facultative anaerobes) Beginning the second day , anaerobic bacteria can be detected in infantile’s edentulous mouth. The pioneer species are usually Streptococci (S. salivaris, S. oralis, S. mitis) which bind to the mucosal epithelium. Metabolic activity of the pioneer community alters the oral enviorment to facilitate colonisation of other species. 13

14. Oral flora after 1 year consists of Streptococcus, Staphylococcus, Neisseria together with Gram negative anaerobes such as Veillonella species. Less frequently isolated are Lactobacillus, Actinomyces, Prevotella and Fusobacterium. The next evolutionary change in this community occurs during and after tooth eruption when two further regions are provided for bacterial colonisation. Gingival crevice Enamel surface 14

15. ENAMEL SURFACE S.mutans S.sanguinis Actinomyces Lactobacillus Rothia GINGIVAL CREVICE Prevotella Porphyromonas Neisseria Capnocytophaga

16. DURING PUBERTY , transition to an adult flora composition can be noticed due to hormonal changes . Spirochaetes Veilonella Prevotella Bacteroids The rise in Prevotella intermedia in plaque during the second trimester of pregnancy has also been ascribed to the elevated serum levels of oestradiol and progesterone which can satisfy the naphthoquinone requirement for growth of this organism. PREGNANCY Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016.

17. WINDOW OF INFECTIVITY Explained by Caufield and his colleagues in 1993. It is the time of initial colonization of the infants oral enviorment with the cariogenic bacteria mutans streptococci (MS). Acquisition of some bacteria optimally occur at certain ages. Children at the age of 26 months are more susceptible for colonisation by mutans streptococci.(initial acquisition of MS) Another window of infectivity for MS is speculated at 6 years of age, when permanent teeth erupt. 17

18. PIONEER COMMUNITY AND MICROBIAL SUCCESSION The first microorganisms to colonise are termed pioneer species , and collectively they make up the pioneer microbial community. These pioneer species continue to grow and colonise until environmental resistance (physical and chemical) is encountered. Physical factors that promote removal include the shedding of epithelial cells (desquamation), and the shear forces from chewing and saliva flow Nutrient availability and unfavourable conditions of redox potential or pH, and the antibacterial properties of saliva, are chemical barriers that can limit growth. Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. 18

19. The pioneer community influences the pattern of microbial succession. Porphyromonas gingivalis , Tannerella forsythia and A. actinomycetemcomitans were detected in the mouths of approximately 10% to 30% of 18-month-old infants. The proportions of putative periodontal pathogens, such as P. gingivalis , T. forsythia and Treponema denticola , in biofilms from mucosal surfaces (especially the tongue and teeth) were found to increase over time in children aged 3 to 12 years Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016.

20. ALLOGENIC AND AUTOGENIC MICROBIAL SUCCESSION Two distinct types of succession have been identified In allogenic succession, factors of non-microbial origin are responsible for an altered pattern of community development. The increase in number and diversity of obligate anaerobes once teeth are present is an example of autogenic succession in which community development is influenced by microbial factors 20

21. MOUTH AS A MICROBIAL HABITAT Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. 21

22. The microbial load is relatively low on such surfaces because of the process of desquamation. The papillary structure of the dorsum of the tongue provides refuge for many microorganisms which would otherwise be removed by mastication and salivary flow. Proteins and glycoproteins present in saliva can influence the oral microbiota by • adsorbing to the tooth surface to form a conditioning film -the acquired pellicle • acting as primary sources of nutrients (carbohydrates and proteins) for the resident microbiota • inhibiting the growth of some exogenous microorganisms. MUCOSAL SURFACE Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. SALIVA 22

23. The mouth is the only normally accessible site in the body that has hard non-shedding surfaces for microbial colonisation . Teeth (and dentures) allow the accumulation of large masses of microorganisms (predominantly bacteria) and their extracellular products, termed dental plaque GCF can influence the microbial ecology by: • removing non-adherent microbial cells; • Introducing components of the host defences , especially antibodies and neutrophils • Acting as a novel source of nutrients for the resident microorganisms . GCF TEETH Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. 23

24. FACTORS INFLUENCING GROWTH OF NORMAL FLORA MISCELLANEOUS FACTORS ANATOMICAL FACTORS HOST GENETICS HOST LIFESTYLE TEMPERATURE HOST DEFENSE pH REDOX POTENTIAL 24

25. HOST DEFENSES ASSOCIATED WITH ORAL MUCOSAL SURFACES REFERENCE-ESSENTIAL MICROBI LOGY for DENTIST Y . Lakshman Samaranayake- 3 RD EDITION 25

26. HOMEOSTASIS IN ORAL CAVITY For an imbalanced dental biofilm community, reducing consumption of dietary sugar, such as use of sugar substitutes, or using target-specific antimicrobial agents, This targeted regulation of cariogenic pathogens may completely or partially reverses the species diversity, which allows the re-growth or re-establishment of acid-sensitive species in the community eventually restoring the balance or homeostasis in the community that is less pathogenic. 26

27. HOMEOSTASIS BREAKDOWN In the human oral cavity, frequent consumption of dietary sugar is a powerful ecological factor Frequent consumption of dietary sugar promotes the overgrowth of sugar-fermentable and acid-producing-and-resistant bacteria This will likely result in population shifts in the biofilm that is characterized by dominance of fewer acid-resistant species, such as S. mutans and Lactobacillus spp. This will reduce or eliminate many acid-sensitive bacteria (blank shapes) in the community, leading to the homeostasis breakdown and thereby predisposing the site to dental caries (tooth decay). 27

28. NUTRITION OF ORAL BACTERIA Oral bacteria obtain their food from a number of sources. These include host resources Host diet Salivary constituents Crevicular exudate Gaseous environment Extracellular microbial products of the neighbouring bacteria, especially in dense communities such as plaque Intracellular food storage 28

29. METABOLISM OF ORAL MICROORGANISMS Oral microorganisms derive nutrients from saliva and GCF. There is an enormous diversity in substrates available and in the metabolic activities of the organisms which colonise the mouth. Carbohydrate metabolism has received much attention because of its role in caries production. End products of such fermentation in the mouth are varied e.G. , Streptococcus mutans produces only lactic acid from sugars, some lactobacilli produce lactic acid and ethanol w hereas yeasts convert glucose to ethanol and CO2. The substrates used are also very varied and many of the anaerobes seen in the mouth are able to utilise amino acids as substrates for fermentation; therefore, periodontal organisms are predominantly proteolytic. 29

30. The wearing of dentures also increases with age and this also promotes colonisation by C. albicans. The dorsum of the tongue harbours the most diverse microbiota, with many Gram-negative anaerobic bacteria being present (e.g., Veillonella , Fusobacterium, Prevotella species and spirochaetes). The incidence of oral candidosis is more common in the elderly , is also to physiological changes in the oral mucosa, malnutrition and to trace element deficiencies. Periodontal pathogens such as Tannerella forsythia, Porphyromonas gingivalis and Treponema denticola can also be detected. Many elderly subjects take a variety of medications , the side effects of which can reduce the flow of saliva and thereby perturb the normal balance of the resident oral microbiota. AGEING 30

31. The risk of cancer rises with age, and cytotoxic therapy or myelosuppression combined with the disease itself is associated with the increased carriage of Candida albicans and non-oral opportunistic pathogens such as enterobacteria (e.g., Klebsiella spp., Escherichia coli, Pseudomonas aeruginosa) and Staphylococcus aureus. Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. Smoking has been shown to affect the composition of the microbiota and is a significant risk factor for periodontal diseases. Smoking is associated with the increased prevalence of members of the genera: Parvimonas , Fusobacterium, Porphyromonas , Treponema and Campylobacter and a reduction in Veillonella , Neisseria and Streptococcus species.

32. BENEFITS OF THE ORAL MICROBIOTA COLONISATION RESISTANCE Resident microorganisms being more effective at: • Attachment to host receptors • Competition for endogenous nutrients • Creating unfavourable conditions to discourage attachment and retard multiplication of invading organisms • Producing antagonistic substances. Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. 32

33. The resident oral bacteria play an important role in general health by via the metabolism of dietary nitrate. Nitrate is present in many leafy green vegetables and beets and is absorbed into the bloodstream during digestion. Circulating nitrate is concentrated by the salivary glands, and approximately 25% of dietary nitrate reappears in saliva where it is reduced to nitrite by the oral microbiota. NITRATE METABOLISM HOST-MICROBE CROSS-TALK Host cell-pattern recognition receptors (e.g., Tolllike receptors) can recognise microbe-associated molecular patterns (e.g., lipopolysaccharide, lipoteichoic acid) and activate multiple signalling pathways, many of which converge on nuclear factor kappa- lightchain -enhancer of activated B cells ( NFĸB ). The host has developed strategies to distinguish between commensal and pathogenic bacteria. Reference-Marsh and Martin’s Oral Microbiology- 6 th edition-2016. 33

34. ORAL MANIFESTATIONS ASSOCIATED WITH COVID-19- CASE REPORT- JULY 2020 A 43-year-old woman tested positive for SARS-CoV-2 for 56 days, period in which several PCRs were performed. Patient developed fever, malaise, dysgeusia and anosmia, diarrhea, and pneumonia, and blood laboratories suggested risk of thrombosis. Reference- 2020 John Wiley & Sons A/S. Published by John Wiley & Sons . Oral Diseases. 2020;00:1–3 . 34

35. It is important to consider that an exhaustive intraoral examination should be performed in patients that were diagnosed with COVID-19 in order to find any oral manifestation that might be related. For instance, appearance of temporal oral pigmented lesions is expected as chloroquine has been used as part of the treatment in patients with COVID-19. TAKE HOME MESSAGE Reference- 2020 John Wiley & Sons A/S. Published by John Wiley & Sons . Oral Diseases. 2020;00:1–3 . 35

36. RESIDENT ORAL MICROBIOTA

37. STREPTOCOCCI Streptococci have been isolated from all sites in the mouth and comprise a large proportion of the resident cultivable oral microbiota. Classification:- α -haemolytic streptococci β -haemolytic streptococci γ -haemolytic streptococci Oral streptococci are generally alpha-haemolytic (partial haemolysis) on blood agar, and early workers called them viridans streptococci.

38. ORAL STREPTOCOCCI ARE CLUSTERED INTO FOUR GROUPS

39. STREPTOCOCCI MUTANS GROUP :- Streptococcus mutans was originally isolated from carious human teeth by Clarke in 1924. Nine serotypes have been recognized (a–h, and k), based on serological specificity of carbohydrate antigens located in the cell wall. Mutans streptococci are recovered almost exclusively from hard, nonshedding surfaces in the mouth, such as teeth or dentures, and can act as opportunistic pathogens, being isolated from cases of infective endocarditis. Epidemiological studies have implicated S. mutans as one of the main causative organisms in the aetiology of enamel and root surface caries. The next most commonly isolated species of the mutans streptococci group is S. sobrinus and is also associated with human dental caries.

40. 2. SALIVARIOUS GROUP:- This group comprises S. salivarius and S. vestibularis. Strains of S. salivarius are commonly isolated from most areas of the mouth, although they preferentially colonise mucosal surfaces, especially the tongue. Streptococcus salivarius produces large quantities of an unusual extracellular fructan* from sucrose, as well as a levanase that can degrade this type of fructan. Streptococcus salivarius is isolated only rarely from diseased sites and is not considered a significant opportunistic pathogen. Streptococcus vestibularis is isolated mainly from the vestibular mucosa of the human mouth. These bacteria do not produce extracellular polysaccharides from sucrose, but do produce a urease* and hydrogen peroxide

41. ANGINOSUS GROUP :- Representative species of this group Stre ptococcus constellatus S. intermedius and S. anginosus are readily isolated from dental plaque and from mucosal surfaces and are important causes of serious, purulent disease in humans, including maxillofacial infections. Streptococcus intermedius is isolated mainly from liver and brain abscesses, whereas S. anginosus and S. constellatus are derived from purulent infections from a wider range of sites. This group does not make extracellular polysaccharides from sucrose.

42. MITIS GROUP :- Two of the most common streptococcal species in the mouth are S. mitis and S. oralis . Streptococcus mitis is subdivided into two biotypes, and these show different distribution patterns in the mouth. Strains of these two species are able to take up extracellular DNA (i.e., they are genetically competent), and this process is facilitated in biofilms like dental plaque where bacteria are in close proximity to one another. Other members of this group include S. parasanguinis (formerly S. parasanguis ) that has been isolated from clinical specimens (throat, blood, urine) Newer species have been described including S. oligofermentans , S. sinensis , S. australis , S. infantis , S. peroris , S. tigurinus and S. dentisani . S. tigurinus and S. sinensis can act as opportunistic pathogens, having been isolated from cases of infective endocarditis. Streptococcus pneumonia can be isolated from the nasopharynx and is a significant opportunistic pathogen, which can acquire and transfer antibiotic resistance genes amongst other members of the mitis group.

43. OTHER GRAM POSITIVE COCCI Granulicatella adiacens is common in the mouth and is an early coloniser of the tooth surface. Other Gram-positive cocci include Gemella species (G. haemolysans and G. morbillorum ), although cells sometimes appear Gram-negative on staining. Originally, strains were placed in the genus, Peptostreptococcus , and representative species included P. micros, P. magnus and P. anaerobius . Enterococci have been recovered in low numbers from several oral sites when appropriate selective media have been used; the most frequently isolated species is Enterococcus faecalis.They can be isolated from the mouths of immuno-compromised and medically-compromised patients, and have been isolated from periodontal pockets that fail to respond to therapy and from infected root canals. Group A streptococci can often be cultured from the saliva of people suffering from streptococcal sore throats and may be associated with a particularly acute form of gingivitis. Staphylococci are found in denture plaque, as well as in immunocompromised patients and individuals suffering from a variety of oral infections.

44. GRAM-POSITIVE RODS AND FILAMENTS ACTINOMYCES Actinomyces species form a major portion of the microbiota of dental plaque. These bacteria have been associated with root surface caries, and their numbers increase during gingivitis. Cells of Actinomyces species appear as short rods whereas those of A. israelii can sometimes appear to be filamentous. Actinomyces radicidentis has been isolated from endodontic infections. Actinomyces israelii can act as an opportunistic pathogen causing a chronic inflammatory condition called actinomycosis . The disease is usually associated with the orofacial region, but it can disseminate to cause deep-seated infections at other sites in the body such as the abdomen. A. gerencseriae is a common but minor component of the microbiota of the healthy gingival crevice, and it has also been isolated from abscesses Actinomyces georgiae is facultatively anaerobic and is also found occasionally in the healthy gingival crevice

45. EUBACTERIUM AND RELATED GENERA Oral eubacteria are restricted to Eubacterium saburreum, E. yurii, E. infirmum, E. sulci, E. saphenum, E. minutum, E. nodatum and E. brachy New genera include Mogibacterium (e.g., M. timidum, M. vescum and M. pumilum), Pseudoramibacter (e.g., P. alactolyticus) and Slackia (e.g., S. exigua), all of which have been recovered from infected root canals. Other new genera include Cryptobacterium (e.g., C. curtum), Shuttleworthia (e.g., S. satelles), Solobacterium (e.g., S. moorei) and Bulleidia (e.g., B. extructa). Many of these bacteria have also been found in periodontal pockets and/or abscesses.

46. LACTOBACILLUS Lactobacilli are commonly isolated from the oral cavity, especially from dental plaque and the tongue, although they usually comprise less than 1% of the total cultivable microbiota in the healthy mouth. These bacteria are highly acidogenic and acid tolerant, and their proportions and prevalence increase in advanced enamel and root surface caries lesions. The most common species are L. casei, L. rhamnosus , L. fermentum , L. acidophilus, L. salivarius , L. plantarum , L. paracasei , L. gasseri and L. oris , but most studies still merely group them as ‘lactobacilli’ or Lactobacillus species. Simple tests with selective media have been designed for estimating the numbers of lactobacilli in patients’ saliva to give an indication of the cariogenic potential of a mouth.

47. OTHER GENERA Propionibacterium species (e.g., P. acnes, P. propionicus) are obligately anaerobic bacteria that are found in dental plaque. Propionibacterium propionicus has been isolated from cases of actinomycosis and lacrimal canaliculitis (infection of the tear duct). Corynebacterium matruchotii and Rothia dentocariosa are also regularly isolated from dental plaque. Rothia mucilaginosa produces an extracellular slime and is isolated almost exclusively from the tongue. Many bifidobacteria are acidogenic and acid tolerating, which supports proposals that they may play a role in dental caries. Bacteria originally described as ‘anaerobic lactobacilli’ have been placed in new genera such as Olsenella, e.g., Olsenella uli, which has been isolated from periodontal pockets, and Atopobium species Filifactor alocis is an asaccharolytic and obligately anaerobic Gram-positive short rod-shaped bacterium that is considered to be a potentially important periodontal pathogen.It has also been found in endodontic infections, peri implantitis and aggressive forms of periodontal disease.

48. GRAM-NEGATIVE COCCI Neisseria are aerobic or facultatively anaerobic Gram negative cocci that are isolated in low numbers from most sites in the oral cavity. These bacteria are among the earliest colonizers of teeth and make an important contribution to plaque formation. Common species include N. subflava, N. mucosa, N. flavescens and N. pharyngis. Moraxella catarrhalis is a commensal of the upper respiratory tract, but it is also a well-established opportunistic pathogen; many strains produce a βlactamase that can lead to complications during antibiotic treatment. Veillonella species have been isolated from most surfaces of the oral cavity although they occur in highest numbers in dental plaque. Lactic acid is the strongest acid produced in quantity by oral bacteria and is implicated in the dissolution of enamel. Veillonella can convert lactic acid to weaker acids (predominantly propionic acid) and so ameliorate the potential damage of saccharolytic bacteria, such as streptococci.

49. GRAM-NEGATIVE RODS FACULTATIVELY ANAEROBIC AND CAPNOPHILIC GENERA :- The only species of Haemophilus found commonly in the mouth is H. parainfluenzae. H. parahaemolyticus is isolated from soft tissue infections of the oral cavity but is probably not a regular member of the oral microbiota. A. actinomycetemcomitans is implicated in a particularly aggressive form of periodontal disease in adolescents. Aggregatibacter actinomycetemcomitans is also an opportunistic pathogen, being isolated from cases of endocarditis, brain and subcutaneous abscesses, osteomyelitis and periodontal disease. A highly virulent clone of A. actinomycetemcomitans has been recognised, whose distribution is restricted to certain adolescents with a high risk of aggressive periodontitis, most of which generally have a North West African origin. Eikenella corrodens has been isolated from a range of oral infections including endocarditis and abscesses, and has been implicated in periodontal disease. Capnocytophaga are found in sub gingival plaque and increase in proportions in gingivitis. A number of species have been recognised including Capnocytophaga gingivalis, C. ochracea, C. sputigena, C. granulosa, C. haemolytica and C. leadbetteri

50. Kingella (e.g., K. oralis) is a coccobacillus that has been isolated from several oral sites. There have been reports of Helicobacter pylori in dental plaque; this species is microaerophilic and is usually isolated from the stomach where it is associated with gastritis, peptic ulcers and gastric cancer. It may be present in the mouth transiently following reflux from the stomach.

51. OBLIGATELY ANAEROBIC GENERA Obligately anaerobic Gram-negative rods comprise a large proportion of the microbiota of dental plaque and the tongue. P. intermedia is associated with periodontal disease whereas P. nigrescens is isolated more often, and in higher numbers, from healthy sites. Porphyromonas gingivalis is isolated primarily from subgingival sites, especially in advanced periodontal lesions, although it has also been recovered from the tongue and tonsils. Porphyromonas gingivalis has numerous fimbriae on its cell surface that mediate adherence to oral epithelial cells and to saliva-coated tooth surfaces, and produces large quantities of surface vesicles that can be shed into the environment. Porphyromonas endodontalis, has been mainly recovered from infected root canals, and Porphyromonas catoniae, is found mainly at healthy sites or in shallow periodontal pockets.

52. SUMMARY BACTERIA (Philip Marsh. Role of microflora in health. Microbial Ecology in Health and Disease 2000; 12: 130–137)

53. FUNGI The main perfect fungi causing oral infection are Aspergillus, Geotrichum and mucor species. The imperfect yeasts, e.g., Candida species are common in the mouth. A large number of other yeast species have been isolated, including C. glabrata, C. tropicalis, C. krusei , C. parapsilosis , and C. guilliermondii , as well as species of Rhodotorula and Saccharomyces. The most common site of isolation is the dorsum of the tongue. The isolation of Candida increases with the presence of intra-oral devices such as dentures or orthodontic appliances, particularly in the upper jaw on the fitting surface as they can attach tenaciously to acrylic.

54. ARCHAEA Archaea have characteristics that make them distinct from either Bacteria or Eukarya and constitute a distinct branch of the phylogenetic tree of life. Archaea are found in complex microbial communities in the gut and mouth. Methanobrevibacter oralis is the main species in the oral cavity, detected in subgingival dental plaque and infected root canals. These organisms obtain energy by the reduction of CO2 to methane, and associations between methanogens and sulphate reducing bacteria with Synergistes and other putative periodontal pathogens have been reported.

55. PROTOZOA Protozoa are defined as unicellular eukaryotic microorganisms that lack a cell wall. Two protozoan species frequently recovered from the mouth are Trichomonas tenax and Entamoeba gingivalis. Molecular techniques can be used to detect these organisms and PCR has detected T. tenax in 2% of healthy oral cavities, increasing to 21% in patients with periodontal disease. Their incidence increases in individuals with poor oral hygiene

56. VIRUSES The virus most frequently encountered in saliva and the orofacial area is Herpes simplex type 1 (HSV1). Cytomegalovirus is present in most individuals. These viruses have been detected in the saliva of symptomless adults. Coxsackie virus A2, 4, 5, 6, 8, 9, 10 and 16 have all been detected in saliva and in the oral epithelium. The detection of these viruses has usually been associated with hand, foot and mouth disease or herpangina HPV types 2 and 4 have been frequently encountered within localised hyperplastic wart-like epithelial lesions of the lips and mouth (verruca vulgaris, condylomata acuminata ) Bacteriophages have been observed in samples of saliva and dental plaque

57. SUMMARY OF ORAL MICROBIAL FLORA

58. 58 CONCLUSION Oral health has a strong influence on the quality of life of an individual and is more than merely preserving the integrity of the teeth and their supporting tissues. An understanding of the relationship between the oral microbiota and the host, and how this relationship can be perturbed by exogenous and endogenous factors (oral microbial ecology), is critical to understanding oral diseases and in developing new preventative strategies.

59. REFERENCES Marsh and Martin’s Oral Microbiology- 6 th edition-2016 ESSENTIAL MICROBI LOGY for DENTIST Y . Lakshman Samaranayake- 3 RD EDITION Textboo o microbiology- dr. C P Baveja BOOKS ARTICLE Article- 2020 John Wiley & Sons A/S. Published by John Wiley & Sons . Oral Diseases. 2020;00:1–3

60. THANK YOU