Antimicrobial Chemotherapy

Question 1

Give three mechanisms by which bacteria can be resistant to antibiotics

Answer 1

1. bacteria produce an enzyme which breaks down the antibiotic (e.g. B-lactamase attacks penicillin)
2. genetic alteration in target site within the organism means that the antibiotic is ineffective (e.g. MRSA)
3. bacteria acquires an efflux pump, which pumps the antibiotic out of the cell (e.g. macrolide resistance)

Question 2

What class do penicillins and cephalosporins belong to?

Answer 2

Beta-lactam antibiotics

Question 3

Give four examples of penicillins

Answer 3

Benzylpenicillin (penicillin G)
Flucloxacillin
Amoxacillin
Co-amoxiclav

Question 4

Give an example of each generation of cephalosporin

Answer 4

1st generation: cephalexin
2nd generation: cefuroxime
3rd generation: ceftriaxone
4th generation: cefepime

Question 5

Give two drug classes which are effective against staph and strep. Give an example of a drug that belongs to each class.

Answer 5

Macrolide: clarithromycin, azithromycin and erythromycin
Lincosamide: clindamycin

(note: macrolides are also useful against atypical pneumonia)

Question 6

Give two drug classes which are effective against Pseudomonas (and other gram-negative organisms). Give an example of a drug that belongs in each class.

Answer 6

Fluoroquinolone: ciprofloxacin
Aminoglycoside: gentamycin

Question 7

Which organisms are sensitive to gentamycin?

Answer 7

Gram-negative bacteria, including pseudomonas
Staph aureus
(NOT streptococcus)

Question 8

Which antibiotic is effective against MRSA? Which class does this drug belong to?

Answer 8

Vancomycin (a glycopeptide antibiotic)

Question 9

How is vancomycin administered?

Answer 9

IV unless treating Clostridium dificile in which case it should be given orally

Question 10

Which antibiotic(s) are effective against Clostridium dificile?

Answer 10

Metronidazole

Vancomycin

Question 11

Give two antibiotics which are used to treat UTIs

Answer 11

Trimethoprim

Nitrofurantoin

Question 12

Give an example of a carbapenem. Which organisms are susceptible to this drug?

Answer 12

Meropenem

Has a wide spectrum, including anaerobes

Question 13

Which organisms are sensitive to metronidazole?

Answer 13

Anaerobes - including Clostridium dificile

Parasites

Question 14

Give an example of a tetracycline, and four organisms that are sensitive to this class of drugs.

Answer 14

Doxycycline

Sensitive organisms:

• chlamydia
• borrelia (Lyme)
• brucella
• rickettsia

Question 15

How to B-lactams work?

Answer 15

B-lactams are bactericidal; they inhibit cell wall synthesis, causing autolysis of the bacteria cell and therefore the death of the organism.

Question 16

Which antibiotic is teratogenic, nephrotoxic and ototoxic?

Answer 16

Gentamycin

Question 17

Are antiviral drugs viricidal or virustatic?

Answer 17

All antivirals are virustatic

Question 18

Give four examples of anti-herpes drugs

Answer 18

Aciclovir
Famciclovir
Ganciclovir
Foscarnet
Cidofovir

Question 19

Give four organisms which are sensitive to aciclovir

Answer 19

herpes simplex virus (HSV)
Epstein-Barr virus (EBV)
varicella zoster virus (VZV)
cytomegalovirus (CMV)

Question 20

Give two examples of nucleoside analogue reverse transcriptase inhibitors. Which virus are they used to treat?

Answer 20

Ziduvudine (AZT)
Lamivudine
Abacavir

Treat HIV infection

Question 21

Give four drugs which can be used to treat hepatitis B

Answer 21

adefovir
tenofovir
entecavir
telbivudine

Question 22

Give three drugs which can be used to treat hepatitis C

Answer 22

interferon alpha
ribavarin (oral)
lamivudine

Question 23

Give two drugs which can be used to treat influenza A and B. What is the condition for administering these drugs?

Answer 23

Zanamavir
Oseltamivir

Must be administered within 48 hours of symptom onset in order to be effective

Question 24

Give four classes of antifungal drugs

Answer 24

Polyenes
Azoles
Allylamines
Echinocandins

Question 25

Which antifungal drugs can be given IV to treat systemic fungal infection?

Answer 25

Amphotericin B

Caspofungin

Question 26

Give two drugs which belong to the polyene class of antifungals. How to polyenes work?

Answer 26

Amphotericin B
Nyastatin

Work by increasing the permeability of the fungal cell wall

Question 27

How do azoles work? Give three drugs which belong in this class

Answer 27

Inhibit ergosterol synthesis

• Fluconazole (acts on yeast)
• Itraconazole (acts on both yeasts and filliforms)
• Voriconazole (treats invasive aspergillosis)

Question 28

What is terbinafine?

Answer 28

An allylamine antifungal agent
Inhibits ergesterol synthesis
Usually used to treat dermatophytes

Question 29

What is caspofungin?

Answer 29

An echinocandin antifungal agent
Inhibits synthesis of glucan polysaccharide
Usually given IV to treat severe candida and aspergillus infections

Question 30

Describe the regime for treating tuberculosis

Answer 30

6 months of Rifampicin and Isoniazid

First two months supplemented with Pyrazinamide and Ethambutol

Question 31

What side effects are associated with Rifampicin?

Answer 31

Red/orange urine
Itch
Thrombocytopenia
(Liver toxicity/hepatitis)

Question 32

What side effects are associated with Isoniazid?

Answer 32

Peripheral neuropathy

Liver toxicity

Question 33

What side effects are associated with Ethambutol?

Answer 33

Visual disturbances

also contra-indicated in renal impairment

Question 34

What side effects are associated with Pyrazinamide?

Answer 34

Rash

Liver toxicity

Question 35

Give an example of a second-line tuberculosis drug

Answer 35

Streptomycin

Question 36

For which organism(s) is benzylpenicillin usually the first choice?

Answer 36

Neisseria meningitidis
Strep pneumoniae
Strep pyogenes

Question 37

For which organism(s) is flucloxacillin usually the first choice?

Answer 37

Staphylococcus aureus

Question 38

For which organism(s) is amoxicillin (and co-amoxiclav) usually the first choice?

Answer 38

Streptococci
Enterococci
Staph aureus
Gram negatives (but not pseudomonas) - co-amoxiclav has better action against gram negatives due to inhibiton of beta-lactamase enzymes

Question 39

For which infections are cephalosporins often the first choice?

Answer 39

Pneumonia and meningitis

• gram-negative organisms (except Pseudomonas)
• streptococci