Antibiotics

Question 1

Define Antibiotic, Bactericidial, Bacteriostatic

Answer 1

Antibiotic = anti-microbial medication
Bactericidial = kills bacteria
Bacteriostatic = inhibits growth of bacteria

Question 2

Outline the structure of bacteria

Answer 2

1-10uM in size
DNA is single chromosome
Independent metabolism
No chromosomes
Cell wall which differs from host organism

Question 3

What colour do peptidoglycan and lipopolysaccharide cell walls stain?

Answer 3

Peptidoglycan cell wall - Gram + blue

Lipopolysaccharide cell wall - Gram - pink (as gram stain can’t get through)

Question 4

What are 4 potential targets of antibiotics?

Answer 4

Bacterial cell wall
Bacterial RNA and protein synthesis
Bacterial DNA structure and function
Folic acid synthesis

Question 5

What are the 5 broad classes of antibiotics?

Answer 5

Beta Lactams (Penicillins and Glycopeptides)
Macrolides
Fluoroquinolones
Nitroimidazoles
Anti-folate

Question 6

What groups of antibiotics does Beta Lactams include?

Answer 6

Penicillins
Cephalosporins
Carbapenems

Question 7

What’s the difference between broad and narrow spectrum antibiotics?

Answer 7

Broad - effective against many bacteria but can kill normal flora
Narrow - limited bacteria effective against so may not kill all pathogens

Question 8

Define minimal bactericidal concentration

Answer 8

It’s the lowest concentration that kills 99.9% of bacteria in a population

Question 9

What are the 4 drugs in the penicillin group of beta lactams and how do they differ in their uses?

Answer 9

Penicillin - mild to moderate infections eg tonsillitis
Flucloxacillin - penicillinase resistant (SSTIs)
Amoxicillin - enhanced uptake with certain bacteria (LRTIs)
Co-Amoxiclav - mixed infections

Question 10

What’s Ceftriaxone good for? What group does it belong do?

Answer 10

Cephalosporin beta-lactam

Broad spectrum: bacterial meningitis, abdominal sepsis, orthopaedic infections

Question 11

What are Quinolones good for? Drug?

Answer 11

Gram negative bacteria
Ciprofloxacin
Bacteriostatic -> bactericidal in high doses
Risk of C.Diff associated diarrhoea

Question 12

What are Nitroimidazoles good for? Drug?

Answer 12

Anaerobic infections (eg abscesses)
Metronidazole

Question 13

What are direct microbiology investigations?

Answer 13

Microscopy culture & sensitivity: uses specific stains (Gram) and antibiotic sensitivity on culture discs

Antigen detection tests
PCR tests

Question 14

What factors need to be considered when choosing an antibiotic?

Answer 14

Need to consider organism and patient
Organism: known organism and sensitivities
Patient: allergy/intolerance, risk of antibiotic-associated infection, severity of infection/immunocompromised, age, pregnancy

Consult BNF antibiotic guidelines based on epidemiology, cost, antibiotic resistance