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Prevotella strains are Gram-negative, non-motile, singular cells that thrive in anaerobic growth conditions. They are generally host associated and
most species exist as obligate anaerobes (Finegold, 1996). Prevotella
species are present in humans, often existing in the oral cavity,
gastrointestinal tract, and vagina (Avguštin et al., 2001). In humans, they can act as an
opportunistic pathogen, causing periodontal and tooth problems such as gingivitis
and periodontitis (Finegold, 1996).
species exist as commensal bacteria in the environment. In the oral cavity, P. intermedia exist in a commensal
environment with species of Actinomyces,
Streptococci, Veillonella, as
well as with many other species (Kolenbrander et al., 2002). These species have
developed cell-cell recognition, as well as having undergone genetic and
metabolite exchange (Kolenbrander et al., 2002). It is believed that the
signaling molecule, autoinducer-2, produced by P. intermedia is used to facilitate communication between
oral bacteria (Kolenbrander et al., 2002). Prevoltella intermedia has also been shown to
cooperate with Peptostreptococcus micros,
enhancing the virulence factor of micros
when creating dentoalveolar infections (Kolenbrander et al., 2002). Prevotella also play an
integral role in carbohydrate digestion of some grazing animals, being one of the
most numerous microbes found in the rumen and hind gut of cattle and sheep (Avguštin
et al., 2001).
Members of this genus are
non-motile and act as opportunistic pathogens (BioProject, 2012).
--- How do abiotic (pH, temperature, nutrients) environments affect Prevotella species?
Growth of Prevotella intermedia favors a slightly basic pH with a temperature held between 34-36˚C (Marcotte and Lavoie, 1998). Additionally, increased hormone production, such as that during adolescence and pregnancy, has been shown to contribute Prevotella proliferation (Kornman and Loesche, 2006).
Several Prevotella species act as opportunistic pathogens, often
penetrating tissues and establishing an infection at mucosal surfaces (Finegold,
1996). There are currently about twenty known species of the genus Prevotella that are known to cause
infection. Prevotella can form abscesses
and genital tract infections (Finegold, 1996). Depleted reduction-oxidation potential within tissues can
contribute to infection (Finegold, 1996).
are known to cause diseases in humans. Prevotella
intermedia is a periodontal pathogen that has been linked to inflammation
of the gums and the related disease of gingivitis (Dorn et al., 1998). The
extensive proliferation of Prevotella
intermedia along with other anaerobic bacteria in the oral cavity has also
been associated with periodontitis (Dorn et al., 1998). Periodontitis is the
detachment of connective tissue along the alveolar bone and is usually preceded
by gingivitis (Dorn et al., 1998). It results in tooth separation, movement,
and swelling of the gums. Subsequent internalization of Prevotella intermedia from periodontal pockets is hypothesized to
be strain specific, being limited to those that possess specific receptors for
fimbriae (Dorn et al., 1998).
Additionally, there is a correlation between coronary heart disease and
periodontal disease that may be linked to the invasion of artery smooth muscle
and artery endothelial cells by Prevotella
intermedia (Dorn et al., 1998).
Species of Prevotella can also cause chronic
sinusitis, chronic otitis media, cervical adenitis, retropharyngeal space
infection, aspiration pneumonia, lung abscess and necrotizing pneumonia (Bacteroides and Prevotella Infections,
2009). Risk of infection by Prevotella
is facilitated by a decrease in the redox potential of tissues, and can be best
prevented through increased oxidation (Finegold, 1996).
Prevotella were formerly classified under Bacteroides
malninogenicus. Prevotella species
have recently been reclassified into two groups: Prevotella melaninogenica and Prevotella
intermedia (Bacteroides Infection, 2011).
Prevotella belong to the phylogenetic
division of Cytophaga-Flexibacter-Bacteroides (CFB) (Avguštin et al., 2001).
This is an ecologically diverse group consisting of many bacteria related by
only a few species (Avguštin et al., 2001). Additionally, species of Prevotella can be categorized as both
“ruminal” and “non-ruminal,” with species in the same category often exhibiting
a closer genetic resemblence (Avguštin et al., 2001). In August of 2007,
two strains of novel species were added to the genus Prevotella based on 16S rRNA gene sequences and phylogenetic
analysis (Ueki et al., 2007). These
two strains, KB7(T) and A42, were the first species of the genus known to exist
in a natural habitat, independent of a mammalian host (Ueki et al., 2007).
are often present on most mucosal surfaces, existing in the oral cavity,
gastrointestinal tract, and female genital tract (Avguštin et al., 2001). Prevotella species thrive on tissues
with decreased oxidation-reduction potentials, such as those with limited blood
supply or tissue necrosis (Finegold, 1996). Growth of Prevotella intermedia favors a slightly basic pH with a temperature
held between 34-36˚C (Marcotte and Lavoie, 1998). Additionally, increased hormone
production, such as that during adolescence and pregnancy, has been shown to
contribute Prevotella proliferation
(Kornman and Loesche, 2006).
It has also been determined that abundance of Prevotella in the GI tract is greater in
persons with diets rich in carbohydrates (Enserink, 2011). In the
gastrointestinal tract, the dominant commensal taxa of Prevotellaceae and Bacteroides
compete to occupy niches within the community. In contrast, Prevotella species in the oral cavity
frequently exist in a complementary habitat with other taxa, such as Treponema (Faust et al., 2012). Prevotella is also found in great
abundance in the gastrointestinal tract of cows and sheep, playing an integral
role in carbohydrate digestion (Bacteroides and Prevotella Infections, 2009).
melaninogenic and Prevotella oralis
are common flora present in the mouth. Prevotella
melaninogenic illustrates selective localization, often found in the
gingival crevice but not other surfaces of the oral cavity (Finegold, 1996).
In a quanitative study of the female genital tract, it was
found that half of the participants had Bacteroides
and Prevotella species present.
Common species of Prevotella isolated
from healthy women included: P. oralis,
P. bivia, P. disiens, P. oris, and P. buccae (Finegold, 1996).
Eleven Prevotella genomes are available via the Broad Institute (Prevotella Group, 2012).
Species of the Prevotella genus are generally bacillus
to almost coccoid bacteria (Finegold, 1996). They are pleomorphic, taking on
different forms during life cycle, and do not form endospores (Bacteroides and Prevotella Infections, 2009). Prevotella melaninogenica and P.
asaccharolytica form gram-negative rods that are dark brown, due to a heme derivative (Finegold,
intermedia can communicate to form biofilms within their habitat that are
often composed of mixed species.
Prevotella are generally obligate anaerobes with a fermentive form of metabolism (Finegold,
1996). Some species, such as P. melaninogenica, require both vitamin K and heme to function (Finegold,
1996). Additionally, the Prevotella
genus has been associated with β-Lactamase activity, partially accounting for
the resistance to some β-lactam antibiotics (Finegold, 1996).
Species of Prevotella are known to produce the
following enzymes: collagenase, neuraminidase, deoxyribonuclease, haparinase,
and proteases (Fingeold, 1996). In the
oral cavity, P. intermedia secretes
salivary IgA proteases that break down IgA1 and IgA2, which facilitates proliferation of P. intermedia and subsequent diseases such as gingivitis and periodontitis (Marcotte and Lavoie, 1998).
Some Prevotella are resistant to β-lactam antibiotics, including
penicillins and cephalosporins (Finegold, 1996). These species include Prevotella that possess a β-lactamase
inhibitor, such as pigmented Prevotella
(Bacteroides Infection, 2011).
Effective antiobiotic treatments for Prevotella
include: metronidazole, amoxycillin/clavulanate, ureidopenicilins, carbapenems,
cephalosporins, clindamycin and chloramphenicol (Bacteroides Infection, 2011). Treatment with some antibiotics,
including aminoglycosides, trimethoprim/sulfamethoxazole, and quinolones, can
contribute to the proliferation of Prevotella
species (Finegold, 1996).
A number of diverse applications have been suggested for Prevotella. One
such application tested the efficacy of a Prevotella
bryantii probiotic for cows suffering from subacute ruminal acidosis. It
was determined that P. bryantii applications
increased fat content in the milk, however the probiotic had no impact on the
pH of the rumen (Chiquette et al., 2012). The role of the changing microbiome associated with lactation and
breast-feeding is also currently being studied. The presence of Prevotella species has been shown to
increase 1-6 months after birth, suggesting a possible role in the infant
microbiome and presenting the opportunity for potential probiotic production
(Cabrera-Rubio et al., 2012).
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