2. Introduction
• The relationship between two organism can be very complex.
• The normal flora present in its normal site in human body provides
some benefits to the host they live in the perfect symbiosis in their
natural habitate.
HOST PATHOGEN
Host’s immune system
Microbal faktor inherent
5. Definition microbial biota
• The human micro biota is the aggregate of microorganisms that
reside on the surface and in deep layers of skin, in the saliva and oral
mucosa, in the conjunctiva, and in the gastrointestinal tracts.
• They include bacteria, fungi, virus. Some of these organisms perform
tasks that are useful for the human host. However, the majority have
no known beneficial or harmful effect.
• Those that are expected to be present, and that under normal
circumstances do not cause disease, but instead participate in
maintaining health, are deemed members of the normal flora
6. WHEN WE GET COLONIZED WITH NORMAL FLORA
• A human first becomes colonized by a normal flora at the moment of
birth and passage through the birth canal. In utero, the fetus is sterile,
but when the mother's water breaks and the birth process begins, so
does colonization of the body surfaces. Handling and feeding of the
infant after birth leads to establishment of a stable normal flora on
the skin, oral cavity and intestinal tract in about 48 hours.
• The composition of a child’s bacterial flora is dependent on the
mother’s micro flora, since she is the primary source for the child’s
bacteria at the outset.
7.
8. Symbiosis
• Symbiosis is define as “life together”. i.e. that two organisms live in an
association with one another.
• Mutualism : Symbiosis as a biological relationship between two or
more organisms where both (host and organism) benefit from one
another. Example : lactobacilli
• Comensalism : In the relationship where the organism benefits but
there is no beneficial or harmful effect on the host, the association
between organisms. Example : Proteus Mirabilis
• Parasitism : The relationship may be in which one organism damage
the other. Example : Entamoeba Hystolytica
9. Characteristics of Microbial Biota
• Indigenous microbiota : Microorganisms that are commonly found on
or in body sites of healthy persons are called normal.
• Resident microbiota : Microorganisms that colonize an area for
months or years
• Transient microbiota.
14. Microbiota function in the skin
• Educates and assists the immune system and alerts immune system to pathogenicity. AMPs
production is upregulated by the presence of Propionibacterium species and other Gram-positive
bacteria. S. epidermidis' Pheno Soluble Modulins have bacteria-killing activity but no effect on
neutrophils
• They compete against pathogenic strains and interfere with their presence. They make the
environment acidic & thereby inhibits growth of organisms. Example, P. acnes converts lipid to
FFA and Lactobacilli produce lactic acid. Both thereby create an acidic environment and inhibits
organisms such as Streptococcus pyogenes (eg. P. acnes) and G. vaginalis (eg. Lactobacilli).
15. Normal Microbiota of the Oral Cavity
• The oral cavity is a
complex environment
that encompasses
distinct, small microbial
habitats, such as
teeth, soft and hard
palate, and tongue,
which form a species-
rich heterogeneous
ecological system.
16. Normal Microflora of the Oral Cavity
• The oral cavity is a complex, heterogeneous microbial habitat
• Saliva contains antimicrobial enzymes
• But high concentrations of nutrients near surfaces in the mouth
promote localized microbial growth
• The tooth consists of a mineral matrix (enamel) surrounding
living tissue (dentin and pulp; Figure 27.4)
17. Normal Microflora of the Oral Cavity
• Extensive growth of oral microorganisms, especially
streptococci, results in a thick bacterial layer (dental plaque)
• As plaque continues to develop, anaerobic bacterial species
begin to grow
18. Normal Microflora of the Oral Cavity
• As dental plaque accumulates, the microorganisms produce
high concentrations of acid that results in decalcification of the
tooth enamel (dental caries)
• The lactic acid bacteria Streptococcus sobrinus and
Streptococcus mutans are common agents in dental caries.
19. FACTORS AFFECTING THE GROWTH OF MICROORGANISMS IN THE
ORAL CAVITY
• Temperature
• Redox potential
• pH
• Nutrients
20. Normal Microbiota of the Oral Cavity
• The mouth contains large numbers of bacteria, with Streptococcus
being the predominant genus.
21. Normal Microbiota of the Respiratory Tract
Respiratory tract
upper
lower
nose, nasopharynx,
oropharynx, and larynx
trachea, bronchi, and
pulmonary parenchyma
The trachea, bronchi, and lungs are protected by the
action of ciliary epithelial cells and by the movement of
mucus. The tissues of these structures are normally
sterile as a result of this protective action
