Microbiology Flashcards
What are the difference between eukaryotes and prokaryotes?
Eukaryotes have a more complex structure, they have multiple chromosomes, a more complex cell wall, larger in size.
What is the order of viruses bacteria and eukaryotes from largest to smallest?
- Eukaryotes
- Bacteria
- Viruses
Name four ways in which bacteria can be classified into species.
- Visible properties
- Physiological properties
- Characteristic surface molecule
- Phylogenetically
What colour are gram negative and gram positive bacteria?
Gram positive – blue
Gram negative – red
What shape are streptococci bacteria?
They are spherical
What shape are bacilli bacteria?
They are rod shaped
What is capsule layer and an advantage of it?
It is the outer layer of some bacteria. It protects bacteria from being injected by white blood cells
What structure allows bacteria to move around?
Flagella
What is the main function of the rigid cell wall found in bacteria?
It provide cell with structural support and protection
How do antibiotics target peptidoglycans?
They target the enzymes that support the synthesis of peptidoglycans thus inhibiting it’s synthesis, which destroys cell structure and integrity
What bacteria contain LPS?
Gram negative bacteria
What is an acid?
Acids are solutions that donate the hydrogen ions when placed in water
What happens during the introduction of acid to the oral system in regards to hydroxyapatite?
- Ions in the oral environment exist in both crystalline states like hydroxyapatite and as free ions
- Ions need to be in constant equilibrium
- When acid is introduced, it is able to bind with free ions in the oral environment and reduce their amount
- In response, crystalline structure is broken down to release more free ions and reach equilibrium
What are the three main pH buffers in saliva and blood?
- A weak acid in a form of carbonic acid
- Phosphates
- Proteins
When can remineralisation occur?
- When the pH stabilises and is above the critical pH
- When there is an adequate amount of free ions
Name 3 components of saliva that have anti-bacterial properties.
- Non-immunological defences
- Physico-chemical barriers
- Immunological barriers
What role does lactoferrin play in reducing bacterial growth?
Lactoferrin is an iron binding found on mucosal surfaces. Lactoferrin is able to deprive microbes of essential iron by binding iron in saliva, lowering the ability to aquire oxygen. Lactoferrin also enhances lysozyme action.
What role do salivary mucins play in reducing numbers of oral bacteria?
Mucins are able to agglutinate microbe and aid their removal
What is acquired pellicle?
It is layer on the tooth surfaces that consists of different protein, lipids and particles that creates the initial protective layer of the tooth
What anti-bacterial enzyme is found in high concentration on tears and saliva? What is it’s mechanism of action against bacteria?
Lysozyme. It is able to hydrolyse peptidoglycans which are present on bacterial cells walls. It than triggers autolysins which cause bacterial degradation.
What are histatins and how do they interfere with the growth of oral bacteria?
Histatins are small peptides which are secreted by submandibular and parotid glands. They are able to interfere with membrane integrity of the bacterial membrane.
What are defensins?
Defensins are small antimicrobial peptides that are present in the granules of phagocytic cells thus are able to kill bacteria there
What is the main immunoglobin found in saliva that prevents attachment of bacterial cells?
It is IgA, even though IgG and IgM are also present in the GCF
What is bacteriostatic?
Means an agent that prevent bacterial growth
What is bactericidal?
It is a substance that kills the bacteria
What is disinfection?
It is the reduction in the number of bacteria
What is sterilisation?
It is the process which totally removes all living matter
What are some of the factors that affect the death rate of bacteria?
- TIme and concentration of bacteria
- Time and concentration of agent
- Time and temperature
What is the effect of temperature on chemical agents?
It could potentially increase the activity of the agent by increasing the exitibility of atoms or it could actually degrade the agent
What are some of the methods of sterilisation available?
- Moist heat with pressure and time
- Dry heat
- Radiation using ultraviolet
- Filtration using cellulose & asbestos
What are some of the infection control methods that should be used in the dental practice?
- Instruments need to be processed by physical removal of debris, appropriate packaging and sterilisation method
- Surfaces in the clinic need to have debris physically removed and a disinfectant needs to be used
- Hand washing with chlorhexidine gluconate
What is a primary ecological niche for oral bacteria?
A primary niche is a group of species populations in an ecosystem. Ecological niches of the mouth such as the tongue, palate and tooth surfaces are able to provide adequete niches for primary colonisation by bacteria
Name 3 distinct areas in the mouth that might be regarded as the primary ecological niches.
- Tooth surfaces
- The tongue
- Buccal mucosa
Name 2 underlying changes that might shift the balance to a dysbiotic microbiome in the oral environment.
- pH
- Oxygen
Explain the significant characteristics of the tooth surface, tongue and palate that enable them to support bacteria?
- Protected surface
- Presence of nutrients
- Non-shedding (mostly)
- Ability to attach to the surface
5,Varied oxygen levels
How does the flow rate of saliva vary during 24hr cycle?
The rate of saliva production is relatively high during the day and decreases significantly during the night time
What are the 4 difference between saliva and gingival crevicular fluid?
- GCF has higher concentration of proteins
- GCF has highrt levels of immunoglobulins
- GCF has a higher concentration of ions
- GCF has lower levels of lysozymes
Explain acidophilic
Bacteria who are able to survive and reproduce in acid
Explain aciduric.
Bacteria that are able to produce acid
What is the approximate pH of an inflamed periodontal pocket?
Diseased periodontal pocket may be pH 8, due to the fact that organisms found in periodontal disease are usually not aciduric
Are obligately anaerobic bacteria such as Porphyromonas gingivalis likely to inhabit the tongue and gingival sulcus. Explain your answer?
They are more likely to inhabit those surface because those surface have low levels of oxygen due to surface tension that is created
What are Fructosyl- and glucosyl-transferases and what is their contribution to the plaque biofilm?
They are a group of enzymes that help to breakdown complex carbohydrates into glucose and fructose. This can be used by the bacteria in the oral environment to grow and proliferate.
Name two exogenous nutrients that promote good oral health. Explain your answer?
- Milk - buffering, calcium and phosphate which may promote remin
- Cheese - stimulate salivary flow
- Sugar substitutes – reduction in carbohydrates
Name 3 host defences that influence oral microbial growth.
- Physical defence – self cleansing, mechanical movement, flow and shedding
- Lysosymes
- PMNs
Name 3 Gram negative bacteria which are thought to lay a significant role in periodontal disease.
- P.Gingivalis
- P. Intermidia
- T. Forsythia
What are gingipains and what bacterium produces them?
Gingipains are a group of proteases secreted by Porphyromonas gingivalis. They are used to clear cytokines thus downregulating host response to the activity of the bacteria
Name 3 functions of gingipans.
- Adherence to and colonisation of epithelial cells
- Disruption and manipulation of the inflammatory response
- Degradation of host proteins and tissues
Name one significant oral organism which is a Spirochaete. What is the role this organism is thought to play in biofilm development?
T.Denticola. It is a helical rod shaped organism that is able to create channels in the biofilm in order to facilitate the movement of nutrients
Give 3 characteristics of the organism Fusobacterium nucleatum
- It’s found in plaque in health and disease
- It ferments CHO and amino acids for energy
- It produces volatile sulphur compounds NH3 and butyric acid
What oral fungi predominates in the oral cavity? Explain what promotes its growth in terms of surfaces and host factors.
It is C.albicans. It usually resides on the tongue and it enjoys the moisture and the surface texture of the tongue
How would you describe a healthy periodontium in regards to bacterial diversity?
Low number of predominatley Gram positive bacteria.
What bacteria predominate in a healthy periodontium?
Gram positive bacteria
What is the main nutritional source in healthy periodontium?
Gingival crevicular fluid
Is there an identified pathogen that causes gingivitis?
No. Gingivitis is a result of bacterial accumulation which could be the same type of bacteria or transition of bacteria from gram positive to gram negative.
How does the number of plaque bacteria change in number with onset of gingivitis?
With gingivitis the bacteria increases in mass by 10-20 times
Describe what bacteria increase in numbers in non-bleeding and bleeding gingivitis
- Bleeding gingivitis – black-pigmented anaerobes increase
- Non-bleading – A.naeslundii and A.israelii
Describe the type of inflammation seen with gingivitis
It is a low grade “surveillance” inflammation
What role does GCF play in gingivitis?
It is able to remove tissue breakdown products, introduce inflammatory mediators and antibodies
