L11 - Antibiotics

Question 1

What are Antibiotics?

Answer 1

they are natural products of fungi and bacteria that dwell in soil. They are then modified chemically to increase their pharmacological properties and antimicrobial effect

Question 2

Describe selective toxicity as a principle of antibiotics?

Answer 2

Due to the differences in structure and metabolic pathways between host and pathogen

Harm microorganisms, not the host

Target in microbe, not host (if possible)

Difficult for viruses (intracellular), fungi and parasites

Variation between microbes

Effect on commensals

Question 3

Describe therapeutic margin as a principle of antibiotics?

Answer 3

active dose vs. toxic effect

Question 4

Describe what Bactericidal Antibiotics are?

Answer 4

kill bacteria

used when the host defense mechanisms are impaired

Required in endocarditis and kidney infection

Question 5

Describe what Bacteriostatic Antibiotics are?

Answer 5

inhibit bacteria

used when the host defense mechanisms are intact

used in many infectious diseases

Question 6

What are broad spectrum antibiotics and give and example?

Answer 6

Effective against many types

Example: Cefotaxime

Question 7

What are narrow spectrum antibiotics and give an example?

Answer 7

Effective against very few types

Example: Penicillin G

Question 8

What are Basic Penicillins used for?

Answer 8

Active against streptococci, pneumococci, meningococci, treopnemes.
Most strains of Staphylococcus aureus are resistant.

Question 9

What are Anti-Staphylococcal penicillins used for?

Answer 9

narrow spectrum, G+ves, beta-lactamase resistant, less potent that benxylpen.

Question 10

What are Broader spectrum penicillins used for?

Answer 10

Spectrum of activity is similar to basic penicillins but also includes some Gram-negative organsims and also enterococci

Question 11

What are Anti-pseudomonal penicillins used for?

Answer 11

extended spectrum beta-lactam antibiotic

also G+ve, G-ve, anaerobes

Question 12

What are Beta-lactam/ beta lactamase penicillins used for?

Answer 12

Spectrum like amoxicillin plus activity against some Gram-negatives and Staph aureus

Question 13

Which class of Antibiotics do penicillins and cephalosporins belong to?

Answer 13

Beta-lactams

the beta lactam ring is the active structure

Question 14

State some common targets on bacteria for antibiotics?

Answer 14

cell wall synthesis

folic acid metabolism

DNA/RNA processing

protein synthesis

cell membrane

Question 15

How do Antibiotics work on the cell wall of Gram-positive bacteria?

Answer 15

The antibiotics can easily diffuse through the cell wall structure made from peptidoglycan, and bind to inhibit the enzymes that make the cell wall

Question 16

How do Antibiotics work on the cell wall of Gram-negative bacteria?

Answer 16

Has to diffuse through an impermeable membrane, and can only get in through certain pores

Question 17

When do we use Antibiotics?

Answer 17

Treatment of bacterial infections

Prophylaxis - close contacts of transmissible infections
carriage rates ( ~80% in outbreaks)
e.g. meningitis
- prevention of infection e.g. tuberculosis

peri-operative cover for gut surgery

• people with  susceptibility to infection

Question 18

What are the different routes of administration of antibiotics?

Answer 18

Community infections often treated orally by GP

Serious infections – hospitalisation - systemic treatment
e.g. i/v rapid delivery, high [blood]
often unable to take oral – vomiting, unconscious,
poor gut absorption due to trauma

Topical - conjunctivitis, superficial skin infections, burns
antiseptic creams, heavy metal ointments