Download Prevotella spp. Habitat and transmission

Fusobacteria & Leptotrichia
Fusobacteria
Fusobacterium nucleatum
Habitat and transmission
Several subspecies of F. nucleatum have been dentified in
different habitats.
These include:
1- F. nucleatum subsp. polymorphum,
found in the healthy gingival crevice, and
2- F. Nucleatum subsp. nucleatum,
recovered mainly from periodonta pockets.
3- A third subspecies is F. nucleatum subsp. vincentii.
Infections are almost invariably endogenous.
.
A photomicrograph of fusobacteria showing characteristic
Gram-negative, cigar-shaped cells with pointed ends.
Characteristics
Gram-negative, strictly anaerobic, cigar-shaped bacilli
with pointed ends ( Cells often have a central swelling.
A Gram-stained smear of deep gingival debris
obtained from a lesion of acute ulcerative gingivitis is
a
These, together with the clinical picture, confirm a
clinical diagnosis of acute ulcerative gingivitis
The endotoxin of the organism appears to be involved in
the pathogenesis of periodontal disea
1- adherence properties
2- F. nucleatum is usually isolated from polymicrobial
infections
Thus, in combination with oral spirochaetes it causes the
classic fusospirochaetal I nfections.
These are:
•
• acute (necrotizing) ulcerative gingivitis or
trench mouth (Vincent’s angina, an ulcerative
tonsillitis causing tissue necrosis, often due to
extension of acute ulcerative gingivitis
• As fusobacteria coaggregate with most other oral
bacteria, bridging organisms between early and
late colonizers during plaque formation
A Gram-stained smear obtained from deep gingival plaque of a
patient with acute ulcerative gingivitis showing the fusospirochaetal
complex. Note: the large cells are polymorphs.
Antibiotic sensitivity and
prevention
Fusobacteria are uniformly sensitive to penicillin
and, being strict anaerobes, are sensitive to
metronidazole.
Regular oral hygiene and antiseptic
mouthwashes are the key to prevention
of oral fusobacterial infections in susceptible
individuals.
Leptotrichia spp
. are oral commensals
previously thought to belong to
the genus Fusobacterium. They
are Gram-negative, strictly
anaerobic, slender, filamentous
bacilli, usually with one pointed
end.
Leptotrichia buccalis, present in
low proportions in dental
plaque, is the sole
representative of this genus
Thank you •
Anaerobic Bacteria
Bacteroides, Porphyromonas
and Prevotella
Bacteroides spp. are mainly restricted to species found
predominantly in the gut and are the most common
agents of serious anaerobic infections;
Bacteroides fragilis is the main pathogen.
Porphyromonas spp. are a saccharolytic pigmented species
and form part of the normal oral flora. They are agents
of periodontal disease and hence considered as
periodontopathic organisms.
• Prevotella spp. include saccharolytic oral and genitourinary
species; some species are periodontopathic.
Collectively, Tannerella, Porphyromonas and Prevotella
species are referred to as black-pigmented anaerobes, as
some organisms from these genera form a characteristic
brown or black pigment on blood agar
Habitat and transmission
Bacteroides species are the most
predominant flora in the intestine (10
cells per gram of faeces
11
They cause serious anaerobic
infections such
as intra-abdominal sepsis, peritonitis,
liver and brain abscesses, and
wound infection.
Characteristics
Strictly anaerobic, Gramnegative, non-motile,
non-sporing bacilli, but
may appear
pleomorphic.
The polysaccharide
capsule is an important
virulence factor.
Pathogenicity
Mainly the result of its endotoxin and
proteases. No exotoxin has been reported.
Other organisms, such as coliforms, are
commonly associated with sepsis.
The latter facultative anaerobes utilize oxygen
in the infective focus and facilitate the growth
of the anaerobic Bacteroides strains.
Consequently, many Bacteroides infections are
polymicrobial in nature.
Bacteroides fragilis
Porphyromonas
Porphyromonas gingivalis
Habitat and transmission
Found almost solely at subgingival sites, particularly in
advanced periodontal disease: considered a consensus
periodontal pathogen.
The three members are:
Porphyromonas gingivalis
Tannerella forsythia
Treponema denticola
are considered the three agents of ‘red complex’ bacteria
almost always associated with periodontal disease
P. gingivalis is sometimes recovered from the tongue and
tonsils.
Characteristics
Non-motile asaccharolytic, short, pleomorphic, Gram
negative coccobacilli.
Pathogenicity
An aggressive periodontal pathogen in both
humans and animals (e.g. guinea pig, monkey,
beagle dogs);
its fimbriae mediate adhesion and the capsule
defends against phagocytosis.
Produces a range of virulence factors including
collagenase, endotoxin, fibrinolysin,
phospholipase many proteases that destroy
immunoglobulins, a fibroblast-inhibitory factor,
complement.
Prevotella
This genus includes a number of pigmented as well
as nonpigmented species that are moderately
saccharolytic; all produce acetic and succinic acid
from glucose.
Prevotella melaninogenica are coccobacilli that
are commonly found in the oral cavity of humans;.
Prevotella spp.
Habitat and transmission
The predominant ecological niche of all Prevotella
species appears to be the human oral cavity.
Strains of Prevotella intermedia are associated
more with periodontal disease,
Prevotella nigrescens is isolated more often from
healthy gingival sites
Pathogenicity
P. intermedia is closely associated with periodontal disease
and shares a number of virulence properties exhibited by P.
gingivalis.
These organisms are classified as belonging to the
‘orange complex’ bacteria associated with the developmental
stages of periodontal disease, and precedes the arrival of the
‘red complex’ group of bacteria
The pathogenicity of other subdivided species non-pigmented
species such as
Prevotella buccae,
Prevotella oralis
Prevotella dentalis
are isolated on occasion from healthy subgingival plaque and
increased its proportions during periodontal
Legionella pneumophila
Habitat and transmission
The organism found in soil and water, including air
conditioning units, domestic and hospital water
supplies, and sometimes in dental unit water
systems.
Spread is known to occur by contaminated aerosols.
.
Characteristics
Gram-negative slender rods,
which stain faintly with the
standard Gram stain
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