Antimicrobials and chemotherapy in clinical practice

Question 1

treatment of a dental access

Answer 1

Primary management
- pulpectomy/incision and drainage
- analgesia
- addition of antibiotics not recommended for localised dental abscess
Antibiotics indicated if
- no possibility of immediate attention by dental practitioner
or
- features of severity/increased risk (eg immunocompromised, valvular heart disease)

for severe infections
- broad spectrum antibiotic

Question 2

how to find evidence of an infection or an access

Answer 2

1) obtain a blood culture
- aerobic and anaerobic
- before initiating parenteral antibiotics
- 5-10ml blood
- can show if infection is spread systemically
2) needle aspirate
- is indicated for gram stain and aerobic and anaerobic cultures

Question 3

other diagnosis if not a dental access

Answer 3

1) Non infectious
- localised lymphadenopathy due to inflammation or a neoplasm
- salivary gland problem due to stone, infection (parotitis) or dehydration/dry mouth
2) neoplasm
- intraoral
- salivary gland
3) unerupted teeth
4) viral
- mumps

Question 4

empirical antibiotics

Answer 4

• from measuring the epidemiology of the presentation we know it is usually caused by these bacteria…
• these are affected by …
• eg best guess which organism and which antibiotic

Question 5

how to know if antibiotics will penetrate the site - indications

Answer 5

pH of the site
antibiotic lipid soluble?

to enter the tissue need to uses arterial benus system

Question 6

what is the standard antibiotic for staphylococcus

Answer 6

flucloxaicillin

Question 7

how do bacteria resist antibiotics

Answer 7

1) change antibiotic target
2) destroy antibiotic
3) prevent antibiotic access
4) remove antibiotic from bacteria

Question 8

what is an organisms sensitivity

Answer 8

1) Primary resistance
- innate property of the bacteria eg Pseudomonas and penicillin
- aerobic bacteria not susceptible to metronidazole (only active once metabolised by the anaerobic metabolism of bacteria)
2) Acquired resistance
- due to mutation or gene transfer
- eg chromosomal such as M. tuberculosis , plasmid mediated eg MRSA (Develops when a plasmid comes from the bacteria across to a different organism, allows genetic material transfer)

Question 9

how does resistance develop

Answer 9

1) intrinsic
- naturally resistant
2) acquired
splits into
1) spontaneous gene mutation
2) horizontal gene transfer
- conjugation
- transduction
- transformation

Question 10

what does acquired resistance split into

Answer 10

1) spontaneous gene mutation

2) horizontal gene transfer

Question 11

how can we detect resistance/sensitivity

Answer 11

antibiotic sensitiity testing
breakpoint plates
chromogenic plates
mechanism specific test
genotypic methods

Question 12

examples of antibiotic sensitivity testing

Answer 12

dilution liquid culutre
agar plate
antibiotic discs
e- tests

Question 13

breakpoint plates

Answer 13

• plates with a specific breakpoint concentration of antibiotic in and see if a given inoculum grows or not
• if it grows on a breakpoint plate, then the antibiotic will not work
• will never reach the concentration required

Question 14

chromogenic plates

Answer 14

• contains enzymes

- if a resistant bacteria is growing, enzymes cause a colour change indicating these bacteria are growing

Question 15

mechanisms specific test

Answer 15

• can look for production of something from a sample

- eg detection of beta- lactamases

Question 16

genotypic methods

Answer 16

e.g. PCR

Question 17

how can the antibiotic work effectively

Answer 17

antibiotic should remain at the binding site for a sufficient period of time in order for the metabolic processes of the bacteria to be sufficiently inhibited

Question 18

time dependant killing

Answer 18

• number of time the concentration is above the MIC during the dosing interval

Question 19

concentration dependant killing

Answer 19

• key parameter is how high the concentration is above MIC

- peak concentration/MIC ratio

Question 20

pharmokinetics

Answer 20

• the movement of a drug from its administration site to the place of its pharmacologic activity and then its elimination from the body

Question 21

what is pharmokinetics a function of

Answer 21

1) its release from the dosage form (eg released in stomach ect)
2) its absorption from the site of administration into the blood stream (eg with or without food, different enzymes in gut)
3) its distribution to various parts of the body, including the site of action
4) its rate of elimination from the body via metabolism (liver) or excretion (kidney) of unchanged drug

Question 22

considerations when providing antibiotics

Answer 22

1) intolerance, allergy and anaphylaxis
2) side effects
3) age
4) renal function
5) liver function
6) pregnancy and breast feeding
7) drug interactions
8) risk of clostridium difficile 5 c’s