Oral Flora I&II

Question 1

What is resident flora?

Answer 1

Consists of a relatively fixed number and types of microorganisms regularly found in a given area at a given age. If disturbed it promptly re-establishes itself. Rapidly acquired during and after birth. Changes continuously throughout life.

Question 2

What is transient flora?

Answer 2

Consists of non-pathogenic or potentially pathogenic microorganisms that inhabit the skin or mucous membranes for hours, or days.
Occurs when there is a perturbation in resident flora.

Question 3

What is a mutualistic relationship?

Answer 3

Microbe and host both mutually benefit e.g., microbe might get food resources and the host gets benefits from the waste products of the microbe could be nutrients

Question 4

What is a commensalistic relationship?

Answer 4

Microbe benefits but the host gets no benefit or harm. E.g, staphylococcus on the skin benefits from our skin but has no effects on humans.

Question 5

What are a pathogenic/parasitic relationship?

Answer 5

Microbe benefits but the host is harmed. Disease situation. E.g. tuberculosis bacterium in human lung benefits but humans get disease

Question 6

What are opportunist pathogens?

Answer 6

Bacteria that are normally not causing disease, but if something changes in the environment then these bacteria can change, become pathogenic and cause disease.

Question 7

When can opportunist pathogens cause disease?

Answer 7

In an immune compromised individual
When they change from their usual location

Question 8

What is a dysbiosis?

Answer 8

When the healthy micro flora environment changes to a disease associated environment

Question 9

What can cause a dysbiosis?

Answer 9

Abuse of antibiotics can destroy beneficial bacteria and promote growth of not beneficial bacteria
Radiation can kill off resident micro flora
Surgery might allow entry of bacteria
Use of immune suppressors may prevent immune system from keeping a balance
Hormones
Acquired immune deficiency

Question 10

What sites in humans should never have bacteria in them and are sterile?

Answer 10

Blood brain, muscles, CSF

Question 11

What is the mouth like in a healthy state?

Answer 11

Balance of healthy bacteria. Symbiosis between microbes and us.

Question 12

What factors might alter the balance of microbes and humans in the mouth?

Answer 12

Inappropriate diet causing decay
Inadequate plaque control due to bad oral hygiene leading to disease associated flora
Impaired saliva flow
Altered host defences e.g. immunosuppression
Lifestyle risk factors e.g. alcohol and smoking

Question 13

What are the 2 major diseases caused by dysbiosis in the oral cavity?

Answer 13

Caries and periodontal disease
Can also lead to systemic diseases

Question 14

What bacteria are part of the healthy micro flora?

Answer 14

Streptococcus, actinomyces, Fusobacterium etc

Question 15

What bacteria cause caries?

Answer 15

Particularly Strep. mutans and lactobacilli

Question 16

How do the caries causing bacteria cause caries?

Answer 16

Produce acids that erode enamel
Tolerate their own acids so survive
Form sugars too which make a gloopy mass for bacteria to live in

Question 17

What bacteria are found in periodontal disease?

Answer 17

Porphyromonas gingivalis, Tannerella forsythia

Question 18

What do periodontitis causing bacteria do to produce periodontitis?

Answer 18

Produce enzymes like proteases and cytotoxic which are immune modulators and cause an inflammatory response

Question 19

Where can pathogens be acquired from?

Answer 19

Within the body
Other people
Animals/animal products
Anywhere on planet eg soil water airborne
Hospital acquired

Question 20

Where do periodontitis causing bacteria come from?

Answer 20

Within us but usually in small numbers so don’t cause disease. If conditions change and they multiple and produce virulence factors then they overgrow and cause disease.

Question 21

Describe the oral ecosystem of the lips, cheek and palate

Answer 21

Biomass limited by desquamated - cells get flowed away along with bacteria
Some surfaces have specialised host cell types
Saliva
Low diversity microflora

Question 22

Describe the oral ecosystem of the tongue

Answer 22

Highly papillated surface with large SA
Acts as a reservoir for obligate anaerobes
Diverse microflora

Question 23

Describe the teeth as an oral ecosystem

Answer 23

Non-shedding surface enabling large masses of microbes to accumulate (dental plaque biofilm)
Teeth have distinct surfaces for microbial colonisation (e.g., smooth surfaces, pits, fissures etc) will support distinct micro flora due to their biological properties
Many obligate anaerobes
Influenced by saliva and GCF
Streptococcus, actinomyces, veillonella, Fusobacterium, prevotella, treponema

Question 24

Describe the oral environment of the gingival crevice/pocket

Answer 24

Pockets are more likely in disease situations eg periodontitis
Health (aerobic bacteria), disease (anaerobic bacteria)

Question 25

What is plaque?

Answer 25

A complex microbial community. Forms in the hard surfaces of the mouth.

Question 26

What does plaque comprise?

Answer 26

Living, dead and dying bacteria and their products Host compounds mainly derived from saliva

Question 27

Where can plaque form in the mouth?

Answer 27

Smooth surface of tooth In fissure Proximal plaque Gingival crevice

Question 28

Where is plaque most easily formed!

Answer 28

Proximal plaque since it is more difficult to clean these areas

Question 29

What is plaque divided into?

Answer 29

Supragingival (above the gingiva) and subgingival (below the gingiva)

Question 30

Describe briefly the gram positive organisms in the oral cavity

Answer 30

Rods, cocci Oxygen tolerance varies Most are fermentative (produce acids)

Question 31

What are the 3 important genera of gram positive bacteria in the oral cavity?

Answer 31

Streptococcus - facultative anaerobic cocci. Produces lactic acid Lactobacillus - facultative anaerobes. Produces lactic acid. Actinomyces - facultative anaerobe

Question 32

What caries are lactobacillus involved in?

Answer 32

Role in dentine caries rather than enamel caries

Question 33

When and where are gram negative organisms found in the mouth?

Answer 33

In poor oral hygiene In subgingival plaque because there is less oxygen here and most gram-negative bacteria are anaerobes

Question 34

Describe briefly the gram negative bacteria in the oral cavity

Answer 34

Range of cocci, rods, filamentous rods, spindle shaped Range of oxygen tolerance mostly strict or facultative anaerobes Some are fermentative, others produce enzymes which break down tissues and lead to inflammation

Question 35

Most important gram negative bacteria

Answer 35

P. gingivalis - major periodontal pathogen Prevotella intermedia - a periodontal pathogen Fusobacterium nucleatum - periodontal pathogen important in formation of dental plaque Aggregatibacter A (AA) associated with aggressive periodontitis Treponema

Question 36

What is treponema?

Answer 36

Group of important in acute periodontal conditions. Spiral shaped bacteria. Very strictly anaerobic and motile. Can see them increase a lot in numbers in periodontitis.

Question 37

Describe the different types of streptococci?

Answer 37

Strep. mutans - infective agent of caries Strep. salivarius - more specific, colonises mucosal surfaces especially the tongue Strep. angiosus Strep. mitis - normal bacterium in oral flora

Question 38

Describe actinomyces

Answer 38

Gram positive Major proportion of dental plaque Found in the normal oral flora Increases in gingivitis and periodontitis Associated with root caries

Question 39

What is virulence?

Answer 39

The ability of an organism to infect the host and cause a disease

Question 40

What are virulence factors?

Answer 40

Molecules that assist a bacterium to colonise the host, cause disease and evade host defences

Question 41

What are the different virulence factors?

Answer 41

Adherence factors, invasion factors, capsules, endotoxins, exotoxins, siderophores

Question 42

Describe adherence factors

Answer 42

Colonisation of mucosal membrane sites using pili/fimbriae to adhere to cells

Question 43

Describe invasion factors

Answer 43

Surface components allowing the bacterium to invade host cells that can be encoded on plasmids. Might inject something into host.

Question 44

Describe capsules

Answer 44

Protect bacteria from opsonisation and phagocytosis

Question 45

Describe endotoxins

Answer 45

E.g., LPS endotoxins on gram-negative bacteria cause fever, changes in BP, inflammation and other toxic events causing the immune response

Question 46

Describe exotoxins

Answer 46

Several toxins produced from pathogenic bacteria, e.g., cytotoxins, neurotoxins and enterotoxins

Question 47

Describe siderophores

Answer 47

Iron-binding factors allowing some bacteria to compete with the host for iron

Question 48

What are most periodontal disease bacteria like?

Answer 48

Gram-negative

Question 49

What are bacterocins?

Answer 49

Antimicrobial factors or molecules that bacteria produce that only work against other bacteria.

Question 50

What do Fusobacterium nucleatum do in periodontal disease?

Answer 50

Bridging organism. Change the environment, pH and oxygen conc so that bacteria that can only grow in low or no oxygen environments start to grow.

Question 51

Describe the flora of a normal healthy dentate mouth

Answer 51

Mostly streptococci and other gram positive cocci and actinomyces Few neissaeria, lactobacilli, filamentous bacteria and staphylococci Also some other bacteria, fungi, protozoa and viruses present