7.2 Antibiotics and their use in dentistry Flashcards
Define an antimicrobial.
An umbrella term for a chemical that inhibits the growth of, or kills, microorganisms.
Includes antibacterials, antivirals, antifungals and antiparasitic agents.
Define an antibiotic.
A chemical compound made by a microorgansim that inhibits growth or kills other microorganisms at low concentration.
Does not include synthetic agents.
Define an antiseptic.
A chemical compound that can inhibit the growth of, or kill, microorganisms at relatively low concentration that can be applied to skin and mucosal membranes, but cannot be used systemically within the human body due to toxicity.
E.g. sodium hypochlorite.
Define a disinfectant.
A chemical compound that can kill microorganisms, but can only be used on surfaces, not on skin/mucosal membranes or systemically within the human body due to high toxicity.
How are antibiotics classified?
Classified accoring to their sites of action.
These sites are sites of structural and metabolic differences between the bacteria and mammalian cells.
Enables selective toxicity to the bacterial oragnisms without damaging host cells.
Name some sites of action of anitbiotics.
- The cell membrane
- Cell wall
- Ribosomes (50S or 30S subunit)
- DNA
- mRNA
What type of bacteria does Metronidazole target?
Anaerobic bacteria
- Targets DNA
- Causes DNA fragmentation, inhibiting protein synthesis
Describe the action of antibiotics that target the bacterial cell wall.
E.g. penicillin
- Prevents cross links in the peptidoglycan cell wall from forming by occupying the active site of transpeptidase (penicllin binding protein, PBP)
- Means the bacterial cell can no longer withstand the pressure exerted on the wall and bursts
- NB: Antimicrobials inhibit the structural integrity of newly synthesised peptidoglycan, don’t brekadown existing peptidoglycan cell walls. Therefore, bacteria need to be actively dividing for these antimicorbials to have any effect.
Why is there a lack of antibiotic discovery?
- Lack of investment by the pharmaceutical industry
- Newer antibiotics will only be used when they are really needed, so drug companies do not see a great profit
- Resistance can develop before the cost of development is recovered
Lack of new abx is contributing to increased antibiotic resistance.
Define antimicrobial resistance.
Defined as resitance of a microorganism to an antimicrobial medicine to which it was originally sensitive.
How does antimicrobial resistance occur?
Antimicrobials place a selection pressure on mcirobial populations, essentially allowing those resistant microbes to survive and proliferate, therefore becoming more prevalent.
Selection pressures -> spontaneous mutations
-> resistance genes
Gene is transferred to all of the bacteria’s progeny via vertical gene trasnfer.
What does the term acquired bacterial resistance refer to?
Bacteria developing resistance not only through vertical evolution, but through the acquisition of foreign resistance genes.
How are foreign resistance genes acquired?
Through horizontal gene transfer (HGT), 3 types:
- Transformation
- Transduction
- Conjugation
Why are antibiotics becoming more prevalent in dentistry?
- Ageing population
- More immunocompromised patients
Both groups more susceptible to oral infection. - Use of implants creates higher likelihood of infection
What % of antibiotic prescribing in primary dental care in the UK is unnecessary?
75%
When are antibiotics indicated in dentistry?
- Acute apical absvess with systemic involvement (pyrexia, malaise, lymphadenopathy)
- Acute apical abscess in medically compromised patients
Abscess/swelling where drainage is not achieved.
What is antimicrobial susceptibility testing?
- Taking a culture of an infection and having it antimicrobial susceptibility tested by a lab
- Example of good antimicrobial stewardship
Barely being carried out by dental professionals.
Increasing number of patients requiring inpatient IV antibiotics because the antibiotics used in primary care are being overprescribed.
How should an oral swab be obtained?
- Always a collection of purulent material (pus), NOT a swab
- Swab more likely to be contaminated with superficial commensal oral microbiota
- Pus aspirate maintains anaerobic environment, more accuracy
Define antimicrobial stewardship.
‘An organisational or healthcare system wide approach to promoting and monitoring judicious use of antimicrobials to preserve their future effectiveness’
What guidlines should be followed regarding antimicrobials in dentistry?
FGDP Antimicrobial Prescribing in Dentistry, Good Practice Guidelines
When and how is amoxicillin prescribed in dental practice?
- First choice antibacterial
- Targets peptidoglycan cell wall
- 500mg tablets or oral suspension
- 3 times a day
- Up to 5 days
When and how is phenoxymethylpenicillin prescribed in dental practice?
- Another first choice antibacterial
- Targets peptidoglycan cell wall
- 500mg 3x a day
- Up to 5days
- Narrower spectrum of activity than amoxicillin
- Preferred first line choice
When and how is clarithromycin prescribed in dental practice?
- Penicllin allergy
- Inhibits bacterial protein synthesis
- 250mg 2x a day
- Can be 500mg for severe infection
- Take for up to 5 days
- Contraindicated in pregnant women, nursing mothers, or patients on warfarin or statins
When and how is metronidazole prescribed in dental practice?
- For patients with penicillin allergy or severe spreading infection
- Strictly for anaerobic bacteria, causes DNA fragmentation
- 200mg tablets
- 400mg 3x a day
- Up to 5 days
- Used in conjunction with amoxicillin or penicillin V in clinical cases of severe spreading infection
- Cannot drink alcohol
- Contraindicated in patients taking warfarin, can cause spontaneous, uncontrolled bleeding
When should you review patients taking antibiotics?
Review 2-3 days after definitive treatment.
When should you refer a patient to hospital?
Which 2 antibiotics should never be prescribed by a dentist in primary care, unless under the recommendation of a senior specialist?
- Clindamycin
- Co-amoxiclav
