Microbial Pathogens and Infectious Agents

Question 1

What is the definition of normal microbiota?

Answer 1

Defined as populations of microorganisms routinely found growing on the body of healthy individuals

Question 2

What is the definition of resident flora?

Answer 2

Microbial species that typically inhabit body sites for extended periods

Question 3

What is the definition of transient microbiota?

Answer 3

Temporary microbiota - pass through the body but don’t stay and become resident

Form associations for a short time and are replaced

e.g. bacteria found in pro-biotic yogurt - become out competed by established resident species

Question 4

What is a feature of a normal microbiota?

Answer 4

• Have a dynamic nature

Question 5

When is a normal microbiota established?

Answer 5

Established during birth process, once established composition of flora is dynamic

Question 6

What causes changes to a normal microbiota?

Answer 6

• Changes in response to physiological
  variation within the host
• Each member of flora ecosystem is
  influenced by presence and condition of
  other members

Question 7

How can the normal microbiota provide protection against potentially harmful organisms?

Answer 7

Normal flora competitively exclude pathogens through:
- covering binding sites used for pathogenic
attachment
- consuming available nutrients
- producing toxic compounds e.g. antibiotics

Question 8

How does the normal microbiota help the development of immune system tolerance?

Answer 8

• Prevents overreaction to harmless microbes/
  substances

Question 9

What are the 3 forms of symbiotic relationships?

Answer 9

• Mutualism
• Commensalism
• Parasitism

Question 10

What is a mutualism relationship?

Answer 10

Association in which both partners benefit
e.g. Bacteria and synthesis of vitamins K and B

Question 11

What is a commensalism relationship?

Answer 11

Association in which one partner benefits and other is unharmed
e.g. flora living on skin

Question 12

What is a parasitism relationship?

Answer 12

Association in which the microbe benefits at expense of host
e.g. pathogenic infection

Question 13

What are the 4 different type of cellular (living) pathogens?

Answer 13

• Parasites e.g. tapeworm
• Protozoa e.g. protozoa
• Fungi e.g. athletes foot
• Prokaryote e.g. leprosy

Question 14

What are the 2 types of acellular (non-living) pathogens?

Answer 14

• Virus e.g. AIDs
• Prion e.g. CJD

Question 15

What is the definition of pathogenicity?

Answer 15

The ability of an organism to produce disease

Question 16

What is the definition of virulence?

Answer 16

the degree of pathology caused by the organism (level of danger)

Question 17

What is the definition of an infection?

Answer 17

The invasion and multiplication of microorganisms - bacteria, viruses and parasites, that are not normally present within the body

Question 18

What does subclinical mean?

Answer 18

Causes no symptoms

Question 19

What is a systemic infection?

Answer 19

Bodywide
When an infection is no longer localised and is spread through the blood or lymphatic vessels around the body.

Question 20

Can microorganisms live in the body and not cause infection?

Answer 20

Yes - e.g. bacteria living in the mouth and intestines are not infectious

Question 21

What are the 8 different classifications of infection?

Answer 21

Primary infection
Reinfection
Superinfection
Secondary infection
Focal infection
Cross infection
Nosocomial infection
Subclinical infection

Question 22

What is a primary infection?

Answer 22

Initial infection with organism in host

Question 23

What is reinfection?

Answer 23

Subsequent infection by same organism in a host (after recovery)

Question 24

What is superinfection?

Answer 24

Infection by same organism in a host before recovery

Question 25

What is secondary infection?

Answer 25

When a new organism may set up an infection in a host whose resistance is lowered by pre-existing infectious disease.

Question 26

What is focal infection?

Answer 26

a localised infection which can spread to other organs or structures in the body e.g. oral disease

Question 27

What is cross infection?

Answer 27

The transfer of infection, especially to a hospital patient with a different infection or between different species of animal.

Question 28

What is nosocomial infection?

Answer 28

Cross infection occurring in hospital

Question 29

What is subclinical infection?

Answer 29

Where clinical effects are not apparent

Question 30

What predominates in the diversity of the oral microbiota?

Answer 30

Bacteria predominate - fungi and viruses also present

Question 31

How many species of oral bacteria are there estimated to be?

Answer 31

~ 700 - 1000 species of oral bacteria

Question 32

How many species of bacteria do most individuals have?

Answer 32

50 - 200 species

Question 33

How what percentage of all oral bacteria can be cultured in the lab?

Answer 33

~50%

Question 34

What are the 5 key stages of enamel pellicle formation? (biofilm)

Answer 34

1. Transport of salivary proteins 2. Initial protein adhesion 3. Formation of dense basal layer 4. Formation of outer globular layer 5. Eventual bacterial adherence

Question 35

What is an example of a classic biofilm?

Answer 35

Dental plaque

Question 36

What are transport limitations resulting in biofilm resistance to antimicrobials?

Answer 36

antimicrobial agents are reactively neutralised in surface layers of biofilm faster than it diffuses into biofilm

Question 37

What are physiological limitations resulting in biofilm resistance to antimicrobials?

Answer 37

nutrient deprived cells are forced into a slow growing or non-growing state. Much less susceptible to a variety of antimicrobial challenges

Question 38

What are spread of resistant phenotype limitations resulting in biofilm resistance to antimicrobials?

Answer 38

Antimicrobial resistance genes may be upregulated or spread from resistant to previously susceptible cells through a variety of mechanisms

Question 39

What are 3 common oral diseases?

Answer 39

Caries, Gingivitis, Periodontitis

Question 40

What is the relationship between healthy teeth and gingivitis?

Answer 40

reversible - supragingival plaque

Question 41

What is the relationship between healthy teeth and periodontitis?

Answer 41

An irreversible reaction - subgingival plaque --> microbes living in very different conditions to supragingival plaque

Question 42

What causes dental caries?

Answer 42

Diet - excess sugars --> dental plaque Gram positive facultative bacteria

Question 43

What causes dental health?

Answer 43

Good oral hygiene Mainly gram positive facultative bacteria

Question 44

What causes periodontal disease?

Answer 44

Lack of hygiene Immune dysfunction Pregnancy Smoking Diabetes - Gram negative anaerobic rods

Question 45

What other systems in the body can periodontal disease affect?

Answer 45

There is a relationship between periodontal disease, cardiovascular disease and other chronic diseases. The common link is inflammation. Prescence of periodontal diseases may be associated with heart attacks, strokes, kidney diseases, diabetes, preterm births and prosthetic joint complications.