Microbial Pathogens and Infectious Agents Flashcards
What is the definition of normal microbiota?
Defined as populations of microorganisms routinely found growing on the body of healthy individuals
What is the definition of resident flora?
Microbial species that typically inhabit body sites for extended periods
What is the definition of transient microbiota?
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
What is a feature of a normal microbiota?
- Have a dynamic nature
When is a normal microbiota established?
Established during birth process, once established composition of flora is dynamic
What causes changes to a normal microbiota?
- Changes in response to physiological
variation within the host - Each member of flora ecosystem is
influenced by presence and condition of
other members
How can the normal microbiota provide protection against potentially harmful organisms?
Normal flora competitively exclude pathogens through:
- covering binding sites used for pathogenic
attachment
- consuming available nutrients
- producing toxic compounds e.g. antibiotics
How does the normal microbiota help the development of immune system tolerance?
- Prevents overreaction to harmless microbes/
substances
What are the 3 forms of symbiotic relationships?
- Mutualism
- Commensalism
- Parasitism
What is a mutualism relationship?
Association in which both partners benefit
e.g. Bacteria and synthesis of vitamins K and B
What is a commensalism relationship?
Association in which one partner benefits and other is unharmed
e.g. flora living on skin
What is a parasitism relationship?
Association in which the microbe benefits at expense of host
e.g. pathogenic infection
What are the 4 different type of cellular (living) pathogens?
- Parasites e.g. tapeworm
- Protozoa e.g. protozoa
- Fungi e.g. athletes foot
- Prokaryote e.g. leprosy
What are the 2 types of acellular (non-living) pathogens?
- Virus e.g. AIDs
- Prion e.g. CJD
What is the definition of pathogenicity?
The ability of an organism to produce disease
What is the definition of virulence?
the degree of pathology caused by the organism (level of danger)
What is the definition of an infection?
The invasion and multiplication of microorganisms - bacteria, viruses and parasites, that are not normally present within the body
What does subclinical mean?
Causes no symptoms
What is a systemic infection?
Bodywide
When an infection is no longer localised and is spread through the blood or lymphatic vessels around the body.
Can microorganisms live in the body and not cause infection?
Yes - e.g. bacteria living in the mouth and intestines are not infectious
What are the 8 different classifications of infection?
Primary infection
Reinfection
Superinfection
Secondary infection
Focal infection
Cross infection
Nosocomial infection
Subclinical infection
What is a primary infection?
Initial infection with organism in host
What is reinfection?
Subsequent infection by same organism in a host (after recovery)
What is superinfection?
Infection by same organism in a host before recovery
What is secondary infection?
When a new organism may set up an infection in a host whose resistance is lowered by pre-existing infectious disease.
What is focal infection?
a localised infection which can spread to other organs or structures in the body
e.g. oral disease
What is cross infection?
The transfer of infection, especially to a hospital patient with a different infection or between different species of animal.
What is nosocomial infection?
Cross infection occurring in hospital
What is subclinical infection?
Where clinical effects are not apparent
What predominates in the diversity of the oral microbiota?
Bacteria predominate - fungi and viruses also present
How many species of oral bacteria are there estimated to be?
~ 700 - 1000 species of oral bacteria
How many species of bacteria do most individuals have?
50 - 200 species
How what percentage of all oral bacteria can be cultured in the lab?
~50%
What are the 5 key stages of enamel pellicle
formation? (biofilm)
- Transport of salivary proteins
- Initial protein adhesion
- Formation of dense basal layer
- Formation of outer globular layer
- Eventual bacterial adherence
What is an example of a classic biofilm?
Dental plaque
What are transport limitations resulting in biofilm resistance to antimicrobials?
antimicrobial agents are reactively neutralised in surface layers of biofilm faster than it diffuses into biofilm
What are physiological limitations resulting in biofilm resistance to antimicrobials?
nutrient deprived cells are forced into a slow growing or non-growing state. Much less susceptible to a variety of antimicrobial challenges
What are spread of resistant phenotype limitations resulting in biofilm resistance to antimicrobials?
Antimicrobial resistance genes may be upregulated or spread from resistant to previously susceptible cells through a variety of mechanisms
What are 3 common oral diseases?
Caries, Gingivitis, Periodontitis
What is the relationship between healthy teeth and gingivitis?
reversible
- supragingival plaque
What is the relationship between healthy teeth and periodontitis?
An irreversible reaction
- subgingival plaque –> microbes living in very different conditions to supragingival plaque
What causes dental caries?
Diet - excess sugars –> dental plaque
Gram positive facultative bacteria
What causes dental health?
Good oral hygiene
Mainly gram positive facultative bacteria
What causes periodontal disease?
Lack of hygiene
Immune dysfunction
Pregnancy
Smoking
Diabetes
- Gram negative anaerobic rods
What other systems in the body can periodontal disease affect?
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.
