Microbiology 1 Flashcards
Define pathogen
A disease causing microorganism
Define opportunistic pathogen
A member of the normal microbiota that causes infection under certain circumstances
Define symbiont
A member of the resident microbiota conferring benefit to the host
Define pathobiont
The capacity of a molecule to cause damage to the host
Define dysbiosis
Lack of balance between host responses and resident microbiota
Define virulence
The degree of pathogenicity
Define pathogenicity
The relative capacity of an organism to cause damage
Define virulence determination
Component of pathogen that causes host damage
What is there a balance between in health?
There’s a balance between microbes and our responses to them
What do neutrophils do in disease?
They migrate to the tooth surface guided by chemokines
Neutrophils enter and protect the gingival tissues
What happens when there’s a build up of plaque in the mouth?
Can lead to the formation of gingivitis
Give some examples of evidence that microbes are asscocaited with perio diseases
- Healthy animals bred in germ free environment exhibit perio disease when given perio
- Cross sectional & longitudinal studies carried out on populations
- Microbiological studies carried out correlation between appearance & prevalence
- Immunological studies show the responses to the pathogen from the body
Which type of plaque forms first in the mouth?
Supragingival plaque forms first
Describe Supragingival plaque
It moves down tooth to root eventually forming subgingival plaque
Name the microbes found in the mouth in health
Gram positive aerobes like cocci & rods that are facultative anaerobes
What happens to the microbiota as gingivitis forms?
The population of obligatory anaerobes increases
Name the microbes found in the mouth in periodontitis
Predominantly Gram negative anaerobes & spirochetes
Why does the microbiology composition change with gingivitis and periodontitis formation?
Organisms thrive and outcompete each other and succession occurs
The change has a lot to do with the nutritional availabilities for microbes
What nutrients do supragingival organisms need to survive?
Sugars from food
Salivary glycoproteins
ECM
What do subgingival organisms depend on?
GCF
Blood flow
Histatins from saliva
Where does fluid flow from in the mouth?
Fluid flows from supra to sub gingiva
What changes occur when pocketing occurs?
- There is an increase in inflammation
- Increased GCF flow
- Haem provides nutrients for subgingival organisms
- As pocket gets deeper, O2 levels drop Obligatory anaerobes thrive
- Slight increase in temp leads to increase in metabolic activity of microbes
- Slight increase in pH More favourable for obligate anaerobes
Go through the ecological plaque hypothesis steps
- Plaque levels increase due to poor oral hygiene
- This leads to the formation of gingivitis
- Inflammation increases
- Environmental changes occur due to an increase in inflammation
- Environmental change instigates ecological shift (Periodontitis) like the increase in gram negative anaerobes
- Periodontal diseases occur due to responses of these anaerobes
When are pathogens present in high numbers?
In disease compared to health
Why is it difficult to distinguish the cause of periodontal disease?
Because it is hard to distinguish which particular pathogen is causing the disease
List some of the reasons why is it is difficult to identify the pathogen responsible for causing periodontal disease
- Episodic nature of the disease- it is inactive then active again
- Hard to sample and detect the bacteria as you have to push through the gram positive area which can lead to contamination
- Organisms are difficult to sort out and group together
- Microbiologists keep changing the names of organisms
- 50% of the microbes are unculturable
Name some gram positive bacteria associated with chronic periodontitis in adults (HINT PEEP)
- Peptostreptococcus stomatis
- Eubacterium brachy
- Eubacterium nodatum
- Parvimonas micras
Name some gram negative bacteria associated with chronic periodontitis in adults
- Porphyromonas Gingivalis
- Prevotella intermedia
- Dialister pneumosintes
- Fusobacterium
- Prevotella loeschii
- Campylobacter rectus
- Treponema spp.
- Tanerella forsythia
How do you carry out a DNA-DNA checkerboard?
- Place DNA from species & DNA from clinical sample & see if hybridisation occurs
- This method has been succeeded by Next generation sequencing
What can be used to determine how many organism are in a sample?
HOMIM
Name some unculturable organism associated with chronic periodontal disease
- Spirochete’s
- T7 phylum
- Methanogens
- Novel phonotypes
Why are methanogens unculturable?
Because they are highly anaerobic
What causes aggressive periodontitis?
It is caused due to abnormalities in neutrophils
Describe localised aggressive periodontitis
Little plaque seen
Many capnophilic bacteria (these like CO2) & strong association with AA
What is necrotising periodontal disease associated with?
Associated with HIV/Stress/Smoking
Name some of the bacteria associated with necrotising periodontal disease
Treponema + fusobacterium OR Prevotella intermedia
What are some classic perio pathogens found in Diabetes mellitus associated gingivitis?
P. Gingivalis & Spirochetes
High proportions of Capnocytophaga are seen
What are some bacteria seen in HIV associated perio diseases?
Candida
