Antibiotics and Resistance

Question 1

What does Bacteriostatic, Bacteriocidal, MIC and MBC mean?

Answer 1

• Bacteriostatic inhibit the growth of bacteria
• Bacteriocidal kill bacteria
• MIC (minimum inhibitory conc)
• MBC (min bacteriacidal conc)

Question 2

What is the ideal Antibiotic?

Answer 2

• Selective toxicity/minimal toxicity to host
• Cidal (i.e. kills bacteria)
• Long half life (e.g. low binding to plasma proteins)
• Appropriate tissue distribution
• Oral & parenteral preparations
• No adverse drug interactions/side effects

Question 3

What is Beta-lactams prescribed by dentists?

Answer 3

Amoxycillin

• Co-amoxiclav provides better pain relief 2-3 days after drainage of dentoalveolar infections but broader spectrum
• Co-amoxiclav linked to AMR & CDI risks
• Co-amoxiclav not suitable for empiric prescribing

Question 4

What are the advantages and disadvantages of Beta-lactam antibiotics?

Answer 4

Advantages

• Well characterised
• Safe
• Spectrum (narrow to wide)
• Variety/choice

Disadvantages

• Resistance
• Rapidly excreted
• Hypersensitivity (1-10%)
• CDI (C. diff infections)

Question 5

What does protein synthesis involve?

Answer 5

Protein synthesis involves Ribosomes moving along mRNA molecules that have been transcribed from DNA.

Prokaryotic Ribosomes are structurally different from eukaryotic Ribosomes

Question 6

Macrolides is and inhibitor of protein synthesis. What is an example of a Macrolides and what does it do?

Answer 6

Erythromycin

1. Bind to 23S rRNA in 50S subunit of ribosome
2. Blocks translocation step in protein synthesis

Question 7

What is another inhibitor of protein example and what is its mode of action?

Answer 7

Tetracyclines

• Actively transported into cell. Binds to 30S subunit. Prevents attachment of tRNA to acceptor sites

Question 8

What are some Antibiotics that inhibit Nucleic acid synthesis?

Answer 8

• Metronidazole
• Trimethoprim
• Fluoroquinolones
• Rifampicin & Rifampin

Question 9

What are Antibiotics we try to avoid using? (4C’s)

Answer 9

• Cephalosporins
• Co-amoxiclav
• Ciprofloxacin
• Clindamycin

Question 10

What are Persistor cells?

Answer 10

Persisters are dormant, non-dividing cells that exhibit multidrug tolerance and survive treatment by all known antimicrobials.

Question 11

What is cross resistance and multiple resistance?

Answer 11

Cross resistance - Single mechanism • closely related antibiotics

Multiple resistance - Multiple mechanisms • unrelated antibiotics

Question 12

What are the stages in Horizontal gene transfer?

Answer 12

1. Bacterial Transformation
2. Bacterial Transduction
3. Bacterial Conjugation

Question 13

What are Antibodies where the agent inhibits cell wall synthesis?

Answer 13

• Penicillins
• Cephalosporins
• Carbapenems
• Glycopeptides

Question 14

What are Antibodies where the agent binds to ribosomes and inhibits protein synthesis?

Answer 14

• Aminoglycosides
• Tetracyclines
• Marcolildes
• Clindamycin
• Chlorampenicol
• Linzeolid

Question 15

Prescribing antbiotics must be kept to a minimum. What are common examples of appropriate use of antibiotics?

Answer 15

• Acute NG
• Spreading Infections - Lymph node involvement, cellulitis
• Sinusitis - Staphylococcus, Streptococcus, Moraxella
• Pericoronitis - Major symptomes, Difficulty swallowing
• Trismus (floor of mouth swelling)

Question 16

Answer 16