• an adult human has 10x as many microbial cells as mammalian cells
  • approximately 1.25kg of microbes
  • at least 1500 different microbial taxa
• indigenous microbia=bacteria, fungi, viruses, protozoans, othr protists, &mite
• also referred to as resident, commensal, or normal flora
• occupy all body surfaces plus orfices

• primarily streptococci (facultatives)
  • also peptostreptococci (anaerobic) &staphylococci including micrococci (facultative)
• most abundant streptococci of the viridans group
  • includes a number of species
  • oral streptococci classified into 4 species groups: mitis, mutans, salivarius, &anginosus

• S. mitis - oral cavity & pharynx
• S. sanguinis (sanguis) - oral cavity --strep throat

• S. anginosus

• S. salivarius - oral cavity, esp. tongue & saliva

• S. mutans - dental plauque, carious teeth
• S. sobrinus - tooth surface, carious teeth

• peptostreptococcus - obligate anaerobes
  • may average up to 20% of subgingival flora in advanced PDD (peridontal disease)
  • have been found in odontagenic & soft-tissue absesses
• staphylococci-micrococci - found in nearly every mouth in small numbers-facultatives
  • staphylococcus aureus - numbers low

• actinomyces - facultatives
  • A. israelii, A. viscosus, A. naeslundii, A. odontolyticus
  • A. naeslundii - role in infection not proven
  • A. viscosus - isolated from calculus & root surface caries(gram-postive rod)
  • A. israelii - actinomycosis

• lactobacillus
  • numbers may correlate w/caries activity but not really pathogenic
  • role in caries development uncertain but are associated w/deep dentinal caries
  • produce lots of lactic acid, doesn't cause caries but plays roll in progress

• Veillonelle - anaerobic
  • 5-10% cultivable organisms on tongue &in saliva - bad breath, bad taste --

Gram-Negative Rods & Filaments

• may constitute nearly 25% of flora in a healthy mouth
  • proporties may double w/gingivitis &PDD
• include both facltative &anaerobic species
• most infections involving gram negative rods are mixed infections
• many associated w/development of PDD
• porphyromonas & prevotella - abscesses, pulmonary &ear infections, wound infections chronic sinusitis, peritonitis - among major cause of PDD

Spriochetes

• common inhabitants of oral cavity
  • gingival sulcus & interproximally
  • most belong to genus Treponema
• in infections usually found in conjunction w/fusiforms
  • ANUG, RT infections
• anaerobic

Predominant cultivable oral flora in a healthy mouth

• gram positive cocci 45-50%
• gram positive rods 20%
• gram negative cocci 16 %
• gram negative rods 10-25%

Fungi

• Candida albicans
  • most common oral yeast
  • incidence in healthy individuals. 10-80%
  • overgrowth if bacterial Flora disturbed

Protozoa

• entamoeba gingival and Trichomonas tenax
•  present in about of adults w/ "clean and healthy mouths"
• increases w/PDD

Viruses as part of the normal flora

• persistent infections
• mostly asymptomatic
• not strict pathogens - often opportunists

Indigenous Flora of the skin

• gram positive
• Staphylococcus and micrococcus
• propini bacterium and dernabacter - propionibacterium acnes

• forehead - 348
• cheek - 548
• back of neck - 211
• shoulder - 43
• axilla - 106
• forearm - 41

• sparsely populated / mostly aerobic species
• staphylococcus aureus and S. epidermidis

• continuously seeded from nasopharynx and saliva / complex and variable microbial
• 80% of microbiota
  • hemolytic streptococci / viridans streptococci
  • non-hemolytic streptococci
  • haemophilius spp.
  • neisseria spp.

• esophagus - mostly transients
• stomach - small numbers of acid tolerant bacteria such as lactobacilli; helicobacter pylori (alcers)
• small intestine - mostly anaerobes
• large intestine - highest numbers
  • mostly anaerobic bacteria, primarily rods
  • 10^11 bacteria per gram of feces

• anterior urethra
  • lactobacilli, streptococci, coagulase-negative staphylococci
  • transiently colonized fecal organisms
• vagina
  • diverse population influenced by hormones
  • staphylococci, streptococci, & enterbacteriacae prior to puberty
  • lactobacilli following puberty

Oral Microflora

• 100million microorganisms per ml of saliva
• represent 400-500 species
• usually 20-40 species constitute normal flora
  • 22 genera predominate

• oral cavity sterile at birth
• intitial colonization fortuitous
• streptococcus salivaius first MO found consistently (by end of 1st day)
• strep up to 80% of flora in neonates
• veillonella
• candida albicans & C. parasilosis (44%)

Development of normal flora continued

• streptococcus sanguis (sanhuinius) by ca.9 months
  • attaches to teeth, most abundant of streptococci
• young children
• children w/mixed dentin

• frequently found in children w/primary dentintion
• high incidence in subgingival plaque of children under3

Porphyromonas Gingivalis

• most strongly associated w/pubertal periodontitis
• detected in subgingival plaque over 60% of children in study
• high incidence in children under3

• caries / PDD
• w/loss of teeth: spirochetes, some strep, lactobacilli, actinobacillus actinomycetemcomitans, porphyromonas gingivalis reduced
• edentulous pts w/out dentures: some spp of strep, spirochetes, yeasts reduced or virtually eliminated

• salivary factors
  • ion content
  • oxidation-reduction potential
  • co2 o2
  • organic components
• host diet

• production of bacteriocins
• production of toxic metabolic end products
• induction of low oxidation-reduction potential
• depletion of essential nutrients
• suppression of adherence
• inhibition of translocation
• degradation of toxins

• enhancement of antibody production
• stimulation of phagocyte production
• stimulation of clearance mechanisms
• augmentation of interferon production
• deconjugation of bile acid