Antibiotics: Mechanism of Action

Question 1

Define infection

Answer 1

Invasion and multiplication of pathogenic microbes

Question 2

Define antibiotic

Answer 2

Antibacterial medication (not including disinfectants) that kill or inhibit growth of bacteria

Question 3

Define broad spectrum antibiotics

Answer 3

Active against many bacteria (may also kill normal flora)

Question 4

Define narrow spectrum antibiotics

Answer 4

Effective against specific pathogens (may not kill all pathogens)

Question 5

Define bactericidal

Answer 5

Kills bacteria by affecting its cell wall

Question 6

Define bacteriostatic

Answer 6

Inhibits growth of bacteria by affecting its RNA or DNA

Question 7

Define minimum bactericidal concentration

Answer 7

The lowest concentration that kills 99.9% of a bacteria population

Question 8

Define minimum inhibitory concentration

Answer 8

The lowest concentration that inhibits visible growth of bacteria

Question 9

Which antibiotic groups are bacterial cell wall targetting?

Answer 9

Beta-lactams:

• Penicillins
• Cephalosporins
• Carbapenems

Glycopeptides

(usually bacteriocidal)

Question 10

Which antibiotic types target bacterial RNA and protein synthesis?

Answer 10

Macrolides

Tetracyclines

Aminoglycosides

(usually bacteriostatic)

Question 11

Which antibiotic types target bacterial DNA structure and function?

Answer 11

Quinolones

Nitroimidazoles

Nitrofurantoin

(bacteriocidal if high dose)

Question 12

Which types of antibiotics target folic acid synthesis?

Answer 12

Trimethoprim

Question 13

Which drugs should be avoided in those with penicillin allergies?

Answer 13

Penicillins

Cephalosporins

Question 14

Which antibiotics are useful in bacterial meningitis, orthopaedic infections, UTIs, LRTIs and abdo sepsis?

Answer 14

Cephalosporins: Ceftriaxone

Question 15

Which antibiotics are most commonly used for LRTIs?

Answer 15

Beta-lactam: Amoxicillin

Question 16

Which antibiotics are most commonly used for skin and soft tissue infections?

Answer 16

Beta-lactam: Flucloxicillin

Question 17

Which antibiotics are most commonly used for mixed infections such as dental abscesses?

Answer 17

Beta-lactams: Co-amoxiclav

Question 18

Which antibiotics are often used in multi-resistant UTIs and complex infections?

Answer 18

Carbapenems: Meropenem

Question 19

Which antibiotics are most effective against atypical bacteria, e.g chlamydia?

Answer 19

Tetracyclines: doxycycline and tetracycline

Question 20

Which antiobiotics are used for anaerobic infections?

Answer 20

Nitroimidazoles: Metronidazole

Question 21

Which antibiotics are effective in gram negative infections (excluding anaerobes) such as MRSA?

Answer 21

Quinolones: Ciprofloxacin

Question 22

What factors should be considered when choosing an antibiotic?

Answer 22

• Known/suspected organism ⁺/_- sensitivities and resistances
• Allergies/intolerances
• Renal and liver function
• Severity of infection/immunocompromised
• Risk of Abx associated infection
• Route of administration
• Interactions with other medications
• Age/ethnic grup
• Pregnancy/breast feeding