The mouth may also affect general health by acting
as a reservoir for opportunistic pathogens. Oral
hygiene is poor among patients in intensive care, and
dental plaque from these patients contains large numbers
of potential respiratory pathogens. Aspiration
of these pathogens (and bacteria implicated in periodontal
disease; Ch. 6) into the lower respiratory
tract can increase the likelihood of serious lung infection,
especially in immunocompromised or elderly
people. Helicobacter pylori is also detected in dental
plaque on occasions, and this organism is strongly
associated with chronic gastritis and peptic ulcers,
and is a risk factor for gastric cancer. Helicobacter
pylori is not a normal bacterial inhabitant of the
mouth, and its presence may be associated with gastro-
oesophagal reflux. Its intermittent persistence in
the mouth is linked with the presence of deep periodontal
pockets, and this carriage may aid its transmission
from person-to-person.
This pathogen may
be retained in dental plaque by selective adherence to
already attached bacteria, namely Fusobacterium spp.,
by a process called coadherence or coaggregation
(see Ch. 5)
Cystic fibrosis (CF) is often accompanied
by lung infection caused by opportunistic pathogens
such as Pseudomonas aeruginosa, Haemophilus influenzae,
Burkolderia cepacia and staphylococci. CF patients
have fewer dental health problems, probably as a
consequence of their long-term intensive antibiotic
therapy. Studies have shown that a number of oral
sites in CF patients can be colonised by P. aeruginosa,
suggesting that the mouth could act as reservoir for
this organism. Evidence of transfer of these bacteria
to dental equipment has been reported, which highlights
the need for effective
cross-infection control
strategies (Ch. 12).
Oral microorganisms can have an impact on the general
health of an individual. Periodontal pathogens, together
with the host’s inflammatory response to subgingival
bacteria, may be risk factors for cardiovascular disease,
preterm or low birth weight babies, or diabetes. Oral
bacteria can act as opportunistic pathogens at distant
sites in the body, e.g. following entry to the blood
stream (bacteraemia) or aspiration into the lungs.
The mouth may also act as a reservoir for pathogenic
bacteria such as Pseudomonas aeruginosa and
Helicobacter pylori, emphasizing the need for effective
infection control strategies in the dental surgery.
The mouth has a resident microflora with a characteristic
composition that exists, for the most part, in
harmony with the host. This microflora is of benefit
to the host and contributes to the normal development
of the physiology and host defences of animals
and humans. Components of this microflora
can act as opportunistic pathogens when the habitat
is disturbed or when microorganisms are found
at sites not normally accessible to them. Dental diseases,
caused by imbalances in the resident microflora,
are highly prevalent and extremely costly to
treat. Dental diseases may also act as risk factors for
more serious medical conditions, such as heart and
pulmonary disease; the mouth can also act as a reservoir
for exogenous pathogens such as Helicobacter
pylori and Pseudomonas aeruginosa, emphasising the
need for effective infection control strategies. 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 microflora and the host, and how
this relationship can be perturbed by exogenous
and endogenous factors, is critical to understanding
oral diseases and in developing new preventative
strategies.
Some of the species described above have flagella
and are motile. The Wolinella and Campylobacter
species have a single flagellum, while Selenomonas
spp. are curved to helical bacilli with a tuft of flagella.
Another helical or curved Gram negative oral
anaerobe is Centipeda periodontii which has numerous
flagella which spiral around the cell. There
have been reports of Helicobacter pylori in dental
plaque; this species 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.
Some newly described genera include: Johnsonii
(J. ignava) and Cantonella (C. morbi), which are associated
with gingivitis and periodontitis, respectively;
Dialister (D. pneumosintes and D. invisus) which can
be found in endodontic infections and periodontitis;
Flavobacterium; and Tannerella forsythia (formerly
Bacteroides forsythus or T. forsythensis) which is commonly
isolated from advanced periodontal disease.
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