x. General Lectures Flashcards
L24: What is the major micoorganism associated with periodontitis?
P. gingivalis
L24: How many links are there in the chain of infection and what are they?
7:
- Infectious agent (virulence factor);
- Resevoirs;
- Portal of Exit;
- Means of Transmission;
- Portal of Entry;
- Susceptible Host.
L24: What does it mean when micro-organisms are highly virulent?
High ability to cause disease
L24: What are exotoxins?
A toxin released by a microorganism
L24: Give an example of an exotoxin.
- Protease (from P. gingivalis);
- Enterotoxin (S. aureus);
- Leukocidin (S. aureus).
L24: What are endotoxins?
A component of a bacterial cell wall (are also pyrogens)
L24: Give an example of an endotoxin.
Lipopolysaccharide (from P. gingivalis and E. coli)
L24: What is an infectious dose (ID50)?
The number of microorganisms required to cause an infection
L24: Give an example of a reservoir.
- Microbes ubiquitous in nature;
- Humans;
- Animals;
- Environment;
- Fomites (contaminated objects/ surfaces).
L24: From what reservoir do the most pathogenic microbes, to humans, come from?
Humans
L24: What is the incubation period (similar to latent period)?
The time between contamination and development of symptoms, varies widely for different infections
L24: What is the problem with longer incubation periods?
- Longer time until onset of symptoms;
- Unaware of infection;
- More contact with humans;
- Greater spread of the disease.
L24: What is the infectious period and does this overlap with the incubation period?
The time in which an infection can be transmitted between humans, this does overlap with the incubation period
L24: What is an asymptomatic carrier?
An infected person with no clinical evidence of disease, though signs and symptoms of the disease may have been evident earlier
L24: What is the difference between a colonisation and an infection?
A colonisation is the presence of a microorganism in a host, with growth and multiplication, but without overt expression (infection)
L24: Give an example of a colonisation, commonly carried in humans.
S. aureus (nose)
L24: What are endogenous reservoirs?
Disease caused bacteria/ microbes that are a normal part of a host’s flora, they can become displaces to another body site (e.g. brain or muscle) or invade deeper tissues (commensals)
L24: What are exogenous reservoirs?
Disease caused by bacteria/ microbes entering a host that are non-commensals (e.g. influenza)
L24: What is the portal of exit and what are the two main modes of exits?
- Escape of microbes from a source to a new host;
- Natural and artificial.
L24: Provide an example of a natural portal of exit.
- Coughing;
- Sneezing.
L24: Provide an example of an artificial portal of exit.
- Blood donation;
- Dental handpick aerosols.
L24: What is the R0 number?
The number of cases one case generates on average over the course of its infectious period
L24: What does R0 < 1 mean?
The infection is likely to die out in the long run
L24: What does R0 > 1 mean?
The infection is likely to spread in the population
L24: What is the general relationship between R0 number and risk?
The higher the R0 number, the higher the risk and greater difficulty infection is to control
L24: What effects the R0 number?
- Duration of infectivity;
- Infectiousness (virulence);
- Number of susceptible people.
L24: Where does the influenza virus primarily target?
Upper and lower respiratory tract (virus shed here)
L24: What is the incubation period of influenza?
2-3 days
L24: When does influenza become infectious?
When symptoms appear, children are infectious for longer
L24: Why does influenza also cause a fever, headache and fatigue?
Release of cytokines (IF and TNF)
L24: What can ‘complicated’ influenza lead to?
- Bacterial pneumonia;
- Ear and sinus infections;
- Worsening of chronic medical conditions (asthma, CVD).
L24: Provide examples of direct contact for the portal of entry.
- Respiration (aerosols);
- Inhalation (all particles);
- Contact (droplets).
L24: Provide an example of in-direct contact for the portal of entry.
Settled particles (face touching)
L24: For patients with underlying health conditions, what is their risk of death from flu compared to a healthy person?
18x more likely to die
L24: Provide examples of susceptible hosts for flu.
- Children aged 2-5;
- Unvaccinated;
- Elderly;
- Pregnant;
- Patients with underlying conditions.
L89: How do local anaesthetics work?
- Stop nerve conductions by blocking the voltage-gated Na+ channels;
- Prevents Na+ influx;
- ## Blocks AP generation and propagation;
L89: What order of neutrons do LAs work on?
First order (peripheral nervous system), do not interfere with CNS
L89: What are the different connective tissue layers of a neuron (outer to inner)?
- Epineurium;
- Perineurium;
- Endoneurium.
L89: What effects the rate at which nerve axons are anaesthetised from a site of injection?
- Proximity to site;
- Number of membranes it has to pass.
L89: After nerves are anaesthetised, which ones wean off first?
The ones that were first to be anaesthatised (usually)
L89: What property makes LAs able to cross membranes?
Lipophilicity
L89: What type of tissue helps to retain LA at the desired site?
Fat
L89: In what order do different types of nerve fibres anaesthetise?
- Ad;
- c;
- Ab;
- Aa.
L89: Why can patients still feel pressures under LA?
Aa fibres are last to be anaesthetised - responsible for proprioception (muscle sense)
L89: Why is it important to avoid injecting LA into blood vessels?
- LAs block Na+ channels in other excitable tissue, e.g. heart muscle;
- Can cause bradycardia and hypotension.
L89: LAs are organic molecules, what are the three components?
- Aromatic region (hydrophobic);
- Ester or amide bond;
- Basic amine side chain (hydrophilic).
L89: B.HCl is a term used to present LAs, what does B.HCl stand for?
B - base
HCl - hydrochloride
L89: In what ‘form’ can LAs cross membranes?
Un-ionised
L89: In what ‘form’ are LAs active?
Ionised
L89: Describe the mechanism of action for a LA to cross a membrane:
- Base and hydro dissociate to become diffusible (non-active);
- Cross membranes as individual ions (B and H+);
- Once inside neuron, bond to become active.
L89: Why are small diameter axons more susceptible to LA block?
- Number of Na+ channels relative to diameter of axon; - Small diameter axons, less Na+ channels to block to prevent action potential.
L89: Are myelinated axons more or less susceptible to LA than non-myelinated axons?
- Na+ channels concentrated at the NOR;
- Requires more energy as more channels.
L89: It is very rare for patients to be allergic to LAs. If they ‘truly’ are, what component are they usually allergic to?
Preservative (as this often changes) or reducing agent
L89: Give an example of an ester LA?
Benzocaine
L89: Give an example of an amide LA?
- Lignocaine (lidocaine);
- Prilocaine;
- Articaine;
- Bupivacaine (surgery).
L89: What are the two most common vasoconstrictors used in LAs?
- Adrenaline;
- Felypressin.
L89: What are the benefits of vasoconstrictors in LAs?
- Prolong effects of LA;
- Concentrates one area;
- Reduces leak of LA;
- Use of less LA;
- Bloodless field to work in.
L89: What are the disadvantages of vasoconstrictors in LAs?
- Reduced blood flow;
- Sometimes need blood flow (perio/ gingival graft).
L89: What receptors do vasoconstrictors in LAs target?
- Adrenreceptors;
- ADH receptors;
- B2 receptors (vasodilation);
- B1 receptors;
- a receptors (vasoconstriction);
- Vascular smooth muscle;
L89: What receptors does adrenaline target on smooth muscle walls?
Alpha receptors (vasoconstriction)
L89: Systemically, what receptors does adrenaline have a greater effect on?
Beta receptors (vasodilators - to lower TPR)
L89: Why do patients sometimes experience palpitations, due to adrenaline?
Increase in HR and heart force
L89: How are ester type LAs inactivated by the body?
- ‘Washout’ from tissues by blood supply;
- Broken down by tissue esterases.
L89: How are amide LAs inactivated by the body?
- ‘Washout’ from tissues by blood supply;
- Broken down by the liver.
L89: Before using an amide LA on a patient, what should you check?
Medical history of liver health/ disease
L89: What does a % solution convert to? e.g. 3% prilocaine
3% = 3g/ 100mL = 30mg/ 1mL
L89: How much prilocaine does a 2mL, 3% cartridge contain?
3g/ 100mL, 30mg/ 1mL, 60mg/ 2mL
L89: How are vasoconstrictor strengths expressed in a LA?
Ratios: e.g. 1: 80,000 (1 part of adrenaline in 80,000 parts of liquid)