7. ORALBACTERIA
● At least 700 species of bacteria are supported by the habitats within
the mouth, such as the surfaces of the teeth and oral mucosa
● Bacteria cause diseases by two major mechanisms: (1) invasion and
inflammation and (2) toxin production.
17. ORALVIRUS
● Viruses are some of the smallest microorganisms
(100 to 300 nm) consisting of a core (genome)
containing either deoxyribonucleic acid (DNA) or
ribonucleic acid (RNA) surrounded by a protein shell
(capsid) and can cause a range of important human
diseases.
● Virus infects the cells that have receptors for the virus
18.
19. ViralPathogenesis
● In lytic infections, virus multiplication in the host cell results in the lysis
of the cell and the release of the newly synthesized virions.
● In persistent infections, the virus survives in the host cell by
synthesizing a small number of virions that do not kill the cell. It can be
followed by a latent infection where the viral genome is maintained in
the cell, and no virions are produced. The viral genome may be
activated at a later time point to produce new virions that may result in
cytopathology.
● Some viruses can transform the host cell into a cancer cell that can
divide without the regular control mechanisms in a normal cell
20. Avirusinfectedcellmaydieasaresultof:
● ’Shut-down’ of host cell protein and nucleic acid
synthesis
● Cell lysis, by the release of progeny virions
● Intracellular release of lysosomal enzymes
● Damage to cell membranes.
21.
22. Oncogenic viruses
● Transform or immortalize the infected cells
● Increasing the cell growth rate
● Causing the loss of contact-inhibition of growth
● Removing growth suppressor molecules in the
cell
● Altering cellular morphology
26. ORALFUNGI
● Candida are fungi that are considered members of the normal oral
microbiota.
● When conditions in the mouth alter to one that favours proliferation of
Candida, a shift to a pathogenic relationship with the host may occur
opportunistic occurrence CANDIDIASIS
● The most prevalent Candida species in mouths is Candida albicans
● Other species : C. glabrata, C. krusei, C. tropicalis, C. parapsilosis ,
etc
27. CANDIDAVIRULENCEFACTORS
Evasion of host defences
Phenotypic switching
Hyphal development
Secreted aspartyl proteinase production
01
02
03
Adherence
Invasion and destruction of host tissue
to the oral epithelium or
surfaces of prosthetic
devices (dentures and
orthodontic appliances)
Adhesin
Hyphal development
Secreted aspartyl proteinase production
Phospholipase production
Carcinogenic nitrosamines production
