This document discusses the microbiology of periodontal diseases. It describes the typical microbiota found in healthy sites, gingivitis sites, and chronic or aggressive periodontitis sites. The microbiota shifts from mostly gram-positive facultative bacteria in health to include more gram-negative anaerobic bacteria in disease. Key pathogenic bacteria associated with periodontitis include Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Aggregatibacter actinomycetemcomitans, and Prevotella intermedia. These bacteria produce virulence factors like proteases, lipopolysaccharides, and leukotoxins that promote tissue destruction.

1. By Dr. Nitika Jain
Post Graduate Student

5.  Bacterial homeostasis in plaque biofilms
would be less likely to be disrupted if the
frequency and depth of acidic conditions
following sugar intake could be reduced. This
could be achieved physiologically by
 (a) inhibitors of acid production,
 (b) consumption of food or drinks containing non-
fermentable sweeteners, and
 (c) the local generation of base (alkali) in plaque.

8.  Virulence factors of periodontal micro-
organisms can be subdivided into
 (1) factors that promote colonization (adhesins),
(2) toxins and enzymes that degrade host tissues,
(3) mechanisms that protect pathogenic bacteria
from the host.

9.  Fimbriae, or pili, are polymeric fibrils composed
of repeating subunits that can extend several
microns from the cell membrane.
 Pili were once thought to be unique to gram-
negative bacteria but have now been identified
in several gram-positive organisms, including
streptococci and actinomyces.
 Strains of P. gingivalis produce two types of
fimbriae, known as the major and minor fimbriae.

10.  The gingipains belong to the cysteine protease
family, which utilize an active site cysteine
residue for catalysis.
 Gingipains are classed as “Arg-gingipains” (RgpA
and RgpB) or “Lys-gingipain” (Kgp), based on
their ability to cleave Arg-Xaa or Lys-Xaa peptide
bonds (Xaa represents any amino acid).
 Gingipains are multifunctional proteins that play
important roles in adhesion, tissue degradation,
and evasion of host responses.

11.  Hyperleukotoxic strains include the JP2 clone
of A. actinomycetemcomitans, which is
uniquely associated with localized aggressive
periodontitis.

12.  Pathogenic bacteria have many and varied
strategies for evading or subverting the host
immune system, including
 (1) the production of an extracellular capsule,
 (2) proteolytic degradation of host innate and/or
acquired immunity components,
 (3) modulation of host responses by binding
serum components on the bacterial cell surface,
 (4) invasion of gingival epithelial cells.

14.  The bacteria associated with periodontal health are
primarily gram positive facultative species and
members of the genera Streptococcus and
Actinomyces (e.g., S. sanguis, S. mitis, A. viscosus,
and A. naelslundii).
 Small proportions of gram negative species are also
found, most frequently P. intermedia, F. nucleatum,
and Capnocytophaga, Neisseria, and Veillonella spp.
 Microscopic studies indicate that a few spirochetes
and motile rods also may be found

15.  Certain bacterial species have been proposed to be protective or
beneficial to the host, including S. sanguis, Veillonella parvula, and
C. ochracea. They are typically found in high numbers at
periodontal sites that do not demonstrate attachment loss
(inactive sites) but in low numbers at sites where active
periodontal destruction occurs.
 Socransky SS, Haffajee AD; JP 63: 322, 1992.
 These species probably function in preventing the colonization or
proliferation of pathogenic microorganisms.
 One example of a mechanism by which this may occur is the
production of H2O2 by S. sanguis; H2O2 is known to be lethal to
cells of A. actinomycetecomitans.
 (Hillman JD, Socransky SS “the relationships between streptococcal
species and periodontopathogenic bacteria in human dental plaque”
Arch Oral Biology 30: 791; 1985)

16.  Microbiologic procedures clearly
demonstrated that the number and
proportions of different subgingival bacterial
groups varied in periodontal health when
compared with the disease state . The total
number of bacteria, determined by
microscopic counts per gram of plaque, are
twice as high in Periodontally diseased sites
than in healthy sites.

18.  On culturing, bacteria from healthy
periodontal sites it consists mainly of
 Gram positive facultative rods and cocci ( 75%)
 In gingivitis, (44%) and
 periodontitis ( 10 – 13%)
 Increase in proportions of gram negative
rods,13% to 40% in gingivitis and 74% in
advanced periodontitis.

20.  Model system for experimental gingivitis –
described by Loe et al (Loe H; JP 36: 177,
1965) and Theilade et al.

21.  The bacteria found in naturally occurring dental plaque-
induced gingivitis (chronic gingivitis) consist of roughly
 equal proportions of gram-positive (56%) and gram-negative
(44%) species,
 facultative (59%) and
 anaerobic (41%) microorganisms.
 Predominant gram-positive species include S. sanguis, S.
mitis, S. intermedius, S. oralis, A. viscosus, A. naelslundii,
and Peptostreptococcus micros.
 The gram-negative microorganisms are F. nucleatum,P.
intermedia, V. parvula, as well as Hemophilus,
Capnocytophaga and Campylobacter spp

22.  Pregnancy associated gingivitis :
 This condition is accompanied by increases in
steroid hormones in crevicular fluid and increases
in the P.intermedia, which uses the steroid as
growth factors.( Kornman KS , Loesche WJ ; Infect
Inhuman 35: 256 , 1982)

23.  Microscopic examination of plaque from sites
with chronic periodontitis have consistently
revealed elevated proportions of spirochetes .
 Cultivation of plaque microorganisms from
sites of chronic periodontitis reveals high
percentages of anaerobic (90%) gram-
negative (75%) bacterial species

24.  In chronic periodontitis, the bacteria most often cultivated at high
levels include P. gingivalis, B. forsythus, P. intermedia, C. rectus,
Eikenella corrodens, F. nucleatum, A. actinomycetemcomitans,
P. micros, and Treponema and Eubacterium.
 When Periodontally active sites (i.e., with recent attachment loss)
were examined in comparison with inactive sites (i.e., with no
recent attachment loss), C. rectus, P. gingivalis, P. intermedia, E.
nucleatum, and B. forsythus were found to be elevated in the
active sites.
 Detectable levels of P. gingivalis, P. intermedia, B. forsythus, C.
rectus, and A. actinomycetemcomitans are associated with disease
progression and elimination of specific bacterial pathogens with
therapy is associated with an improved clinical response.

25.  Recent studies have documented an association
between chronic periodontitis and viral
microorganisms of the herpes viruses group,
most notably Epstein-Barr Virus-1 (EBV-1) and
human cytomegalovirus (HCMV).
 ( Contreras A, Slots J: JPR; 35: 3, 2000)
 Presence of subgingival EBV-1 and HCMV are
associated with high levels of putative bacterial
pathogens, including P. gingivalis, B. forsythus,
P. intermedia, and T. denticola

26.  Localized aggressive periodontitis develops
around the time of puberty, is observed in
females more often than in males, and
typically affects the permanent molars and
incisors.
 The microbiota associated with localized
aggressive periodontitis is predominantly
composed of gram-negative, capnophilic,
and anaerobic rods.

27.  Microbiologic studies indicate that almost all LJP sites
harbor A. actinomycetemcomitans ( Moore WE ; JPR: 22;
235, 1987)
 Other organisms found in significant levels include P.
gingivalis, E. corrodens, C. rectus, E nucleatum, B. capillus,
Eubacterium brachy, and Capnocytophaga spp. and
spirochetes.
 Herpesviruses, including EBV-1 and HCMV, also have been
associated with localized aggressive periodontitis.
 (Michalowicz BS, Ronderos M; “ human herpes virus and P.
gingivalis are associated with juvenile periodontitis” JP 71: 981,
2000)

28.  After initial colonization of the first permanent
teeth to erupt ( molars and incisors), immune
defenses are stimulated to produce opsonic
antibodies.
 Bacteria antagonist to A.a may colonize the
periodontal sites and inhibit A.a from further
colonization.
 A.a may loses its toxin producing capacity for
unknown reasons.
 A defect in cementum formation may be
responsible for the localization of the lesions.

29.  Acute inflammation of the gingival and periodontal
tissues characterized by necrosis of the marginal
gingival tissue and interdental papillae.
 Microbiologic studies indicate that high levels of
 P. intermedia and spirochetes are found in necrotizing
ulcerative gingivitis lesions.
 Spirochetes are found to penetrate necrotic tissue and
apparently unaffected connective tissue.
▪ (Lisgarten MA, Socransky SS; “ relative distribution of bacteria at
clinically healthy and periodontally diseased sites in humans” JCP
5:115; 1978)

30.  Periodontal abscess are acute lesions that result in very
rapid destruction of the periodontal tissues.
 Often occur in patients with untreated periodontitis but
can be seen in maintenance phase or in the absence of
periodontitis also ( for example associated with impaction
of a foreign objects or with endodontic problems)
 Clinical symptoms :
 Periodontal pathogens are commonly found in significant
numbers in periodontal abscesses include F. nucleatum, P.
intermedia, P. gingivalis, P. micros, and B. forsythus.
(Newman MG, Socransky SS ; JPR 12: 120, 1997)

31.  Periimplantitis refers to inflammatory process affecting
tissues around already osseointegrated implant & results
in loss of supporting bone.
 Healthy periimplant pockets are characterized by high
proportions of coccoid cells, low ratio of anaerobic &
aerobic species, low numbers of peiodontal pathogens.
 Implants with periimplantitis reveals species such as A.a, P.
gingivalis, T. forsythia, P. micros, C. rectus, Fusobacterium,
& Capnocytophaga are isolated from failing implants.
 Other species such as p. aeruginosa,
enterobacteriaceae
C. albicans, & staphylococci are
also detected around implants.

32.  Lee et al. used the cluster method developed by
Socransky et al.to analyze the microbiota
associated with healthy implants and study the
implant and host-related factors able to
influence the microbial film.
 Rams et al. detected “corn cob” morphology
around healthy implants and “brush forms”
around failing fixtures.
▪ (Rams TE, Link CC Jr (1983) Microbiology of failing dental
implants in humans: electron microscopic observations. J Oral
Implantol 11:93–100)

34.  Forms: multiple biotypes
5 serotypes ( a to e)
on the basis of
difference in
polysaccharides.
 Strains from patients in
Africa have an increased
leucotoxin production.

35.  It grows as white, translucent, smooth, non
hemolytic colony on blood agar.
 Preferably identified on a specific growth
medium ( with vancomycin and bacitracin as
antibiotics to suppress other species)under 5
to 10% CO2.

36. Small, non-motile, Gram-negative saccharolytic,
capnophilic, round-ended rod that forms small,
convex colonies with a "star-shaped" center

37. Leukotoxin
it forms the pore in
neutrophil
Lipo granulocytes,
polysaccharide monocytes, and Collegenase
Protease
lymphocytes which destruction of
Endotoxin able to cleave Ig G
consequently die of connective tissue
osmotic pressure
(Baehni et al. 1979),
a cytolethal
distending toxin .

38.  A. actinomycetemcomitans has been shown,
in vitro, to have the ability to invade cultured
human gingival epithelial cells (Blix et al.
1992, Sreenivasan et al. 1993), human
vascular endothelial cells (Schenkein et al.
2000) and buccal epithelial cells in vivo.

39.  It is a non motile, spindle shaped, highly pleomorphic
rod & gram negative obligate anaeobe.
 Culture condition & identification: It takes 14 days to
form minute colonies, only under anaerobic
conditions & needs several growth factors (N-
acetylmuramic acid) from other species (e.g; F.
nucleatum).
 Pathogenicity: It produces several Proteolytic
enzymes that are able to destroy immunoglobulin &
factors of complement system. It also induces
apoptotic cell death.

40.  This organism was found in higher numbers
in sites of destructive periodontal disease or
periodontal abscesses than in gingivitis or
healthy sites (Lai et al. 1987, Herrera et al.
2000, Papapanou et al. 2000).

41.  Is non motile,
pleomorphic (coccal to
short) rod & gram
negative obligate
anaerobe.
 P. gingivalis is a
member of "black- The black-pigmented colony is an
pigmented isolate of Porphyromonas gingivalis
Bacteroides" group

42.  It grows anaerobically , with dark
pigmentation ( brown, dark green, or black)
on blood agar because of a metabolic end
product from blood( hemin)

43. proteases
• Destruction of Ig,
complement
factors, heme-
sequestering hemolysin collagenases
proteins,
degradation of host
cell collagemnase
inhibition

44.  P. gingivalis can inhibit migration of PMNs
across an epithelial barrier (Madianos et al.
1997) and has been shown to affect the
production or degradation of cytokines by
mammalian cells (Darveau et al. 1998,
Fletcher et al. 1998, Sandros et al. 2000).

45. Prevotella group are
short , round ended
non motile gram
negative rods
They grow
anaerobically , with
dark pigmentation ( The dark-pigmented
colonies are isolates of Prevotella intermedia
brown black colonies)
on blood agar.

46. The levels have been shown to be particularly
elevated in acute necrotizing ulcerative
gingivitis ( Loesche et al. 1982)
in certain forms of periodontitis (Tanner et al.
1979, Dzink et al. 1983, Moore et al. 1985,
Maeda et al. 1998, Herrera et al. 2000,
Papapanou et al. 2000),

47.  F. nucleatum is a Gram-
negative, anaerobic, cigar
shaped bacillus with
pointed ends that has been
recognized as part of the
subgingival microbiota.
 It grows anaerobically on
blood agar.
 Several serotypes are
 F. nucleatum ss nucleatum
 F. nucleatum ss
polymorphum
 F. nucleatum ss vincentii F. Nucleatum on specific medium
 F. periodonticum

49.  F. nucleatum is prevalent in subjects with periodontitis
(Papapanou et al. 2000, Socransky et al. 2002) and
periodontal abscesses (Her rera et al. 2000, Newman MG,
Socransky SS ; JPR 12: 120, 1997).
 Invasion of this species into human gingival epithelial cells
in vitro was accompanied by an increased secretion of IL-8
from the epithelial cells (Han et al. 2000).
 The species can induce apoptotic cell death in
mononuclear and polymorphonuclear cells (Jewett et al.
2001) and cytokine, elastase and oxygen radical release
from leukocytes (Sheikhi et al. 2000).

50.  C. rectus is a Gram-negative,
short rod, curved ( vibrio) or
helical.The motility is due to polar
flagellum.
 The organism is unusual in that it
utilizes H2 or formate as its
energy source.
 It was first described as a
member of the "vibrio corroders",
a group of short nondescript rods
that formed small convex, "dry
spreading" or "corroding"
(pitting) colonies on blood agar
plates.
 C. rectus has been shown to
produce a leukotoxin, and is less
virulent and less proteolytic than
P. gingivalis

51.  E. corrodens is a Gram-negative, capnophilic,
asaccharolytic, regular, small rod with blunt
ends.
 E. corrodens has also been found in association
with A. actinomycetemcomitans in some lesions
of LJP (Mandell 1984, Mandell et al. 1987).
 E. corrodens has been shown to stimulate the
production of matrix metalloproteinases (Dahan
et al. 2001) and IL-6 and IL-8 (Yumoto et al.
1999).

52.  P. micros is a Gram-positive, anaerobic, small,
asaccharolyticcoccus.
 Two genotypes can be distinguished with the
smooth genotype being more frequently
associated with periodontitis lesions than the
rough genotype (Kremer et al. 2000).
 P. micros in combination with either P.
intermedia or P. nigrescens could produce
transmissible abscesses (van Dalen et al.
1998).

53.  The organisms may be recognized by their curved shape,
tumbling motility and, in good preparations, by the
presence of a tuft of flagella inserted in the concave side.
 The Selenomonas spp. are Gram-negative, curved,
saccharolytic rods.
 Moore et al. (1987) described six genetically and
phenotypically distinct groups isolated from the human
oral cavity.
 Selenomonas noxia was found at a higher proportion of
shallow sites (PD < 4 mm) in chronic periodontitis subjects
compared with similar sites in periodontally healthy
subjects (Haffajee et al. 1998). Further, S. noxia was found
to be associated with sites that converted from
periodontal health to disease (Tanner et al. 1998).

54.  E. nodatum, Eubacterium brachy and
Eubacterium timidum are Gram positive,
strictly anaerobic, small, pleomorphic rods.
 They are often difficult to cultivate,
particularly on primary isolation, and appear
to grow better in roll tubes than on blood
agar plates.

55.  Spirochetes is a group of spiral,
motile organisms.
 They are helical rods 5 to 15µm
long with a diameter of o.5µm.
 They have 3 to 8 spirals.
 Spirochete has been implicated
as the likely etiologic agent of
acute necrotizing ulcerative
gingivitis by its presence in large
numbers in tissue biopsies from
affected sites (Listgarten &
Socransky 1964, Listgarten The sample is
1965). dominated by large spirochetes with
the typical cork-screw appearance.

56.  At least 15 species of subgingival spirochetes have been
described, spirochetes are combined in a single group or
groups based on cell size; i.e. small, medium or large.
 Spirochetes includes T. denticola, T. vincentii, T. socranskii,
often associated with periodontitis.
 Some spirochetes have capacity to migrate within GCF &
penetrate epithelium & connective tissue.
 Some have capacity to degrade even dentin
 T. denticola produces Proteolytic enzymes that can destroy
IgA, IgM, IgG, or complement factors.

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58.  Four major viral families are associated with the main
viral oral diseases of adults, as follows:
 1. The group of herpesviruses contains eight different
members that all are enveloped double-stranded DNA
viruses. In the oral cavity, they are related to different
ulcers, tumors, and other oral pathoses.
 2.Human papillomaviruses are grouped within five
genera and are nonenveloped double-stranded DNA
viruses. In the oral cavity, they are related to ulcers,
tumors, and oral pathoses.
12/27/2011 DENTAL PAQUE 58

59.  3. Picornaviruses are all nonenveloped,
single-stranded RNA viruses. In the oral
cavity, they are related to ulcers and different
oral pathoses
 4. Retroviruses. All retroviruses are
enveloped single-stranded RNA viruses. In
the oral cavity, they are related to different
tumors and oral pathoses.
12/27/2011 DENTAL PAQUE 59

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64.  The majority of isolates are Candida, and the
most prevalent species is C. albicans.
Together with C. albicans, some of the most
common opportunistic fungal pathogens in
humans are C. tropicalis, C. glabrata, C. krusei,
C parapsilosis, C. guilliermondii, and C.
dubliniensis.

66.  Only a few parasites affect the oral cavity, but an
increasing body of literature claims that oral protozoa
are more common than previously appreciated.
 Depending on the type of infection, the parasitic
infectious agents can be divided into two categories:
1.those that induce local infections and those that
induce systemic infections with indirect effects on the
oral cavity. The former group comprises saprophytes
(such as Entamoeba gingivalis and Trichomonas tenax)
2.that have the potential to turn into opportunistic
pathogens, or free-living amoebae that occasionally
become invasive but seldom present clinically.

67.  Archaea are single-celled organisms that are
distinct from the bacteria as they are from
eukaryotes. The role of archaea in oral diseases
is only beginning to be explored. Methanogenic
archaea produce methane from hydrogen gas
(H2)/carbon dioxide (CO2) and sometimes from
formate, acetate, methanol, or methylamine.
These organisms have been isolated from
patients with periodontal disease by enriching
cultures with H2 and CO2.

68.  Subsequently, a clear correlation between the
presence of archaeal DNA and periodontal disease
was established. (Lepp PW, Brinig MM, Ouverney CC, et
al: Methanogenic Archaea and human periodontal
disease. Proc Natl Acad Sci U S A 2004;) 101:61-
76).Despite these findings, virtually nothing is known
about the role of archaea in periodontitis.
 Archaea have also been detected in endodontic
infections, and again their contribution to disease is
unknown. (Vianna ME, Conrads G, Gomes BP, et al:
Identification and quantification of archaea involved in
primary endodontic infections. J Clin Microbiol 2006;
44:12-74.)

69.  The periodontal microbiota is a very complex
ecologic system with many structural and
physiologic interactions among the resident
bacteria and between the bacteria and the
host. It is clearly possible that levels of a
particular species may be elevated as a result
of environmental changes produces by the
disease process and may not be a causative
agent. It is also difficult to ascertain the
specific etiologic pathogens in periodontitis.

70.  Newman, Takei, Klokkevold, Carranza.
Carranza’s Clinical Periodontology, 10th Edition
and 11th Edition
 Lindhe, Lang, Karring. Clinical Periodontology &
Implant Dentistry, 5th Edition.
 Philip D Marsh, Michael V Martin, Oral
Microbiology, 5th Edition.
 Perio 2000 - 49:60, 2009
 Perio 2000 - Volume 52 Issue 1, Pages 7 - 121
(Feb 2010)
 “Advnces in dental research” ADR 1997 11: 176
 Philip D. Marsh