Antimicrobials in clinical practice

Question 1

Dental abscess antibiotics

Answer 1

Amoxicillin 500mg tds x 5/7
Or
Penicillin V 500mg qds x 5/7

Question 2

Considerations when giving antibiotics

Answer 2

Are antibiotics necessary?
What is the site of infection?
What is the organism sensitivity?
What is the appropriate or available route of administration?
What antibiotics are safe for the patient?

Question 3

Are antibiotics necessary?

Answer 3

Is there a non antibiotic option?
Is there evidence of infection?
Is there evidence of a bacterial infection?
Is the bacteria colonising or actually causing disease?

Question 4

Dental abscess - primary management

Answer 4

pulpectomy / incision and drainage
analgesia
The addition of antibiotics is not recommended for a localized dental abscess.

Question 5

Dental abscess- antibiotics indicated if

Answer 5

No possibility of immediate attention by a dental practitioner,
Or
Features of severity / increased risk …

Question 6

Features of severity or increased risk

Answer 6

Signs of severe infection e.g. fever, lymphadenopathy, cellulitis, diffuse swelling.
Systemic symptoms e.g. fever or malaise.
A high risk of complications e.g. people who are immunocompromised or diabetic or have valvular heart disease.

Question 7

Is it a dental abscess? **

Answer 7

Evidence of infection?

Obtain a blood culture
(aerobic and anaerobic) before initiating parenteral antibiotics.
Needle aspirate is indicated for Gram stain and aerobic and anaerobic culture

Question 8

Dental abscess - differential diagnosis

Answer 8

NON-INFECTIOUS
Localized lymphadenopathy due to other infection or a neoplasm.
Salivary gland problem due to stone, infection (parotitis), or dehydration/dry mouth.
Neoplasm: 
-intraoral.
-salivary gland.
Unerupted teeth
VIRAL: mumps

Question 9

What is the site of infection?

Answer 9

What organisms should be covered?

Which antibiotics will penetrate that site?

Question 10

Pharyngitis vs dental abscess

Answer 10

Pharyngitis: Streptococcus pyogenes
EBV
Dental abscess:
Viridans group streptococci
Anaerobes
Gram negative rods

Question 11

Bacteria associated with dental infection

Answer 11

Bacteroides
Fusobacterium
Actinomyces
Peptostrep
P. melaninogenica
S. viridans
S. aureus
Haemophiius
T. spp.
(know gram and an/aero)

Question 12

Antimicrobials and oral infections: penicillin

Answer 12

S. sanguis (viridans)
N. gonnorhoeae
T. spp.
Anaerobes +/-

Question 13

Antimicrobials and oral infections: Flucloxacillin

Answer 13

S. aureus

Question 14

Antimicrobials and oral infections: Ampicillin

Answer 14

S sanguis (viridans)
N. gonnorhoeae
H. influenzae (+/-)
T. spp
Anaerobes +/-

Question 15

Antimicrobials and oral infections: Cefuroxime

Answer 15

S sanguis (viridans)
S. aureus (+/-)
N. gonnorhoeae
H. influenzae
T. spp
Anaerobes +/-

Question 16

Antimicrobials and oral infections: clindamycin

Answer 16

S sanguis (viridans)
S. aureus
Anaerobes

Question 17

Antimicrobials and oral infections: erythromycin (macrolides)

Answer 17

S sanguis (viridans)
S. aureus (+/-)
H. influenzae (+/-)

Question 18

Antimicrobials and oral infections: Gentamicin

Answer 18

S sanguis (viridans)
S. aureus (+/-)
N. gonnorhoeae
H. influenzae
T. spp.

Question 19

Antimicrobials and oral infections: metronidazole

Answer 19

Anaerobes ++

Question 20

Primary and acquired resistance

Answer 20

Primary Resistance
-innate property e.g. Pseudomonas and penicillin
Acquired Resistance
-due to mutation or gene transfer
-chromosomal e.g. M.tuberculosis, plasmid mediated e.g. MRSA

Question 21

How do bacteria resist antibiotics?

Answer 21

Change antibiotic target
Destroy antibiotic
Prevent antibiotic access
Remove antibiotic from bacteria

Question 22

How does resistance develop?

Answer 22

Intrinsic - naturally resistant
Acquired
-spontaneous gene mutation
-horizontal gene transfer –> conjugation, transduction, transformation

Question 23

How do we detect resistance/ sensitivity?

Answer 23

Antibiotic sensitivity testing
Breakpoint plates
Chromogenic plates
Mechanism-specific tests e.g. detection of beta-lactamases
Genotypic methods such as PCR for known resistance conferring genes e.g. Rifampicin resistance probe

Question 24

Antibiotic sensitivity testing

Answer 24

Dilutional liquid culture MIC and MBC
Antibiotic discs
E-tests

Question 25

Breakpoint plates

Answer 25

plates with a specific 'breakpoint' concentration of antibiotic in and see if a given inoculum grows or not

Question 26

Lowest MIC

Answer 26

Does not necessarily mean best antibiotic Also consider -pharmacokinetics, -protein binding -distribution into the site of infection, -exposure of an organism to an antibiotic needed for its eradication

Question 27

Antimicrobials are molecules that work by binding target site on bacteria

Answer 27

Defined as points of biochemical reaction crucial to the survival of the bacterium -penicillin-binding proteins in cell wall -cell membrane -DNA -Ribosomes -Topoisomerase IV or DNA gyrase Crucial binding site will vary with the antibiotic class

Question 28

Antibiotic must bind to target site(s) in bacterium

Answer 28

Penetrate outer membrane (penetration resistance), Avoid being pumped out of the membrane (efflux pump resistance), Binding site can change its molecular configuration Remain intact as a molecule (e.g., avoid hydrolysis by beta-lactamases)

Question 29

Drug must not only attach to its binding target but also

Answer 29

must occupy an adequate number of binding sites, which is related to its concentration within the microorganism

Question 30

To work effectively, the antibiotic should

Answer 30

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 31

Two major determinants of bacteria killing include

Answer 31

concentration and the time that the antibiotic remains on these binding sites

Question 32

Concentration-dependent killing

Answer 32

Key parameter is how high the concentration is above MIC Peak conc / MIC ratio -aminoglycosides -quinolones

Question 33

Time dependent killing

Answer 33

Key parameter is the time that serum concentrations remain above the MIC during the dosing interval: t>MIC -beta-lactams (penicillins, cephalosporins, carbapenems, monobactams), -clindamycin, -macrolides (erythromycin, cla rithromycin), -oxazolidinones (linezolid),

Question 34

What is the appropriate or available route of administration?

Answer 34

And dosage interval/ duration | e.g. Strep pharyngitis: Penicillin V, oral, 6 hourly, 10 days

Question 35

What antibiotics are safe for the patient?

Answer 35

- intolerance, allergy and anaphylaxis - side effects - age - renal function - liver function - pregnancy and breast feeding - drug interactions - risk of Clostridium difficile (5 ‘C’s)

Question 36

Risk of C. difficile

Answer 36

``` 5 Cs Ciprofloxacin Clindamycin Cephalosporins Co-amoxiclav (augmentin) Carbapenems, e.g. meropenem ```

Question 37

Start Smart

Answer 37

do not start antimicrobial therapy unless there is clear evidence of infection take a thorough drug allergy history initiate prompt effective antibiotic treatment within one hour of diagnosis (or as soon as possible) in patients with severe sepsis or life-threatening infections. Avoid inappropriate use of broad-spectrum antibiotics comply with local antimicrobial prescribing guidance document clinical indication (and disease severity if appropriate), drug name, dose and route on drug chart and in clinical notes* include review/stop date or duration obtain cultures prior to commencing therapy where possible (but do not delay therapy) prescribe single dose antibiotics for surgical prophylaxis where antibiotics have been shown to be effective document the exact indication on the drug chart (rather than stating long term prophylaxis) for clinical prophylaxis

Question 38

Then Focus

Answer 38

reviewing the clinical diagnosis and the continuing need for antibiotics at 48*-72 hours and documenting a clear plan of action - the ‘antimicrobial prescribing decision’ the five ‘antimicrobial prescribing decision’ options are: 1. Stop antibiotics if there is no evidence of infection 2. Switch antibiotics from intravenous to oral 3. Change antibiotics – ideally to a narrower spectrum – or broader if required 4. Continue and document next review date or stop date 5. Outpatient Parenteral Antibiotic Therapy (OPAT) it is essential that the review and subsequent decision is clearly documented in the clinical notes and on the drug chart where possible eg stop antibiotic