Chapter 5 - Infections

Question 1

Which antibiotics and/or classes of antibiotics work to inhibit:

A) cell wall synthesis
B) protein synthesis
C) nucleic acid synthesis

Answer 1

A) cell wall synthesis:
B-lactams = Penicillins, cephalosporins, monobactams, carbapenems
Glycopeptides = vancomycin, teicoplannin

B) protein synthesis: 
Aminoglycosides = gentamicin, amikacin 
Macrolides 
Tetracyclines 
Clindamycin 
Fusidic acid 
Linezolid 

C) nucleic acid synthesis
Quinolones
Rifampicin
(Metronidazole, sulfonamides and trimethoprim work to inhibit folate synthesis)

Question 2

What are your clinical signs and symptoms of an infection?

Answer 2

• Fever, aches and pain
• Presence of pus, swelling or redness in the potentially infected site
• new onset confusion (particularly in elderly)
• drowsiness, irritability and poor appetite in children
• changes in blood pressure, heart rate or respiratory rate

Question 3

What are the biochemical results indicating an infection?

Answer 3

• Raised or depressed white cell count
• raised neutrophils
• raised C-reactive protein
• altered platelet levels
• raised erythrocyte sedimentation rate
• worsening renal function

Question 4

Which antibiotics are the safest to use in pregnancy?

Answer 4

Penicillins and cephalosporins

Question 5

What is another name for Benzylpenicillin?

Answer 5

Penicillin G

Question 6

Are penicillins bacteriostatic or bactericidal?

Answer 6

Bactericidal

Question 7

What is the mechanism of action of gentamicin?

Answer 7

Gentamicin = aminoglycoside antibiotic.

Disrupts bacterial protein synthesis by binding to the 30S ribosomal subunits and causing misinterpretation of mRNA.

Question 8

What is the difference between time-dependent and concentration-dependent antibiotics?

Answer 8

Concentration dependent:
e.g gentamicin

Increasing baceriocidal activity with increasing concentration of drug, Continues to have bacteriocidal activity even after the concentration of antibotic has fallen below the MIC.

Time dependent:
e.g vancomycin

Increasing bacteriocidal activity does NOT occur with increasing amounts of antibiotics. Therapetutic effect only occurs within therapeutic range i.e 10-20mg/L for vancomycin. When antibiotic levels fall below MIC, therapeutic effect ceases, therefore next dose needs to be given ON TIME to maintain therapeutic levels.

Question 9

What is used for the prophylaxis of rheumatic fever or group A streptococcal infection?

Answer 9

Rhemuatic fever = untreated throat infection as a result of group A streptococcus (Gram +ve)

Phenoxymethylpenicillin

Question 10

Are aminoglycosides bactericidal or bateriostatic?

Answer 10

bactericidal

Question 11

Aminoglycosides are active against gram positive or gram negative bacteria?

Answer 11

Mostly gram negative

Question 12

Treatment with aminoglycosides should generally not exceed ………. days.

Answer 12

7

Question 13

How is gentamicin usually dosed in adults with normal renal function?

Answer 13

5mg/kg - based on IBW

Question 14

In adults with impaired renal function, how do we dose gentamicin?

Answer 14

3mg/kg - less than 20mL/min

Question 15

What serious side effects may occur with gentamicin?

Answer 15

Nephrotoxicity and ototoxicity

Question 16

Carbapenems are active againt what types of bacteria?

Answer 16

broad- spectrum: good cover against gram positive and gram negative

Question 17

Carbapenems are not active against which superbug?

Answer 17

MRSA

Question 18

Cephlasporins are active against what types of bacteria?

Answer 18

Broad spectrum: good cover against gram positive and gram negative

Question 19

Which two cephlasporins are suitable for the treatment of CNS infections i.e meningitis?

Answer 19

Cefotaxime and ceftriaxone - all other cephlasporins penetrate cerebrospinal fluid poorly

Question 20

What are the 1st generation cephlasporins?

Answer 20

Cefalexin
Cefradine
Cefadroxil

Question 21

What are the 2nd generation cephlasporins?

Answer 21

Cefaclor

Cefuroxime

Question 22

What are the 3rd generation cephlasporins?

Answer 22

Cefotaxime
Ceftazidime
Ceftriaxone

Question 23

What is the cautionary and warning labels associated with oral cefuroxime?

Answer 23

Take with or after food - poorly absorbed, therefore given with food maximises absorption

Question 24

Macrolides are active against what types of bacteria?

Answer 24

Broad spectrum: good cover against gram positive and gram negative

Also includes cover against atypicals - Chlamydia, Legionella and Mycoplasma

Question 25

Which macrolide antibiotic has a once daily dosing and why?

Answer 25

Azithromycin - long tissue half-life of 2-4 days

Question 26

What is the method of administration for benzylpenicillin?

Answer 26

IV - BenPen is inactivated by gastric acid

Question 27

Why should phenoxymethylpenicillin not be used for serious infections?

Answer 27

Absorption is unpredictable and plasma concentrations variable

Question 28

Phenoxymethylpenicillin is used in sickle cell disease as prophylaxis against what type of bacteria?

Answer 28

Pneumococcal

Question 29

Which penicillin is the only one active against penicillinase-resistant penicillin - namely staphlycocci?

Answer 29

Flucloxacillin - which is generally the sole indication for the use of flucloxacillin

Question 30

Tazocin is active against which types of bacteria?

Answer 30

Broad spec: good cover against gram positive, gram negative and anaerobes

Question 31

Is Tazocin active against MRSA?

Answer 31

No

Question 32

Quinolones are active against which types of bacteria?

Answer 32

Broad spec: gram positive and gram negative, but more effective against gram negative bacteria

Question 33

Are quinolones indicated against MRSA

Answer 33

No - many staphylococci are resistant to quinolones

Question 34

Moxifloxacin has been associated with which two potentially life-threatening adverse effects?

Answer 34

QT- prolongation

life-threatening hepatotoxicity

Question 35

Tetracyclines are active against which types of bacteria?

Answer 35

Broad specrum - gram positive and gram negative

Question 36

Why should tetracyclines not be given to children under 12, pregnant and breastfeeding women?

Answer 36

• Children under 12 years (deposition in growing bone and teeth, by binding to calcium, causes staining and occasionally dental hypoplasia)
• Should not be given to pregnant women; effects on skeletal development have been documented in the first trimester in animal studies. Administration during the second or third trimester may cause discoloration of the child’s teeth, and maternal hepatotoxicity has been reported with large parenteral doses.

Question 37

Glycopeptide antibiotics are active against which types of bacteria?

Answer 37

Aerobic and anaerobic gram positive bacteria. Also active against MRSA

Question 38

What monitoring requirements are needed for systemic treatment with ketonconazole?

Answer 38

ECG - one week before and one week after intitiation of therapy, then as clinically indicated thereafter

Serum cortisol: Monitor adrenal function within one week of initiation, then regularly thereafter. When cortisol levels are normalised or close to target and effective dose established, monitor every 3–6 months as there is a risk of autoimmune disease development or exacerbation after normalisation of cortisol levels

LFTs: Monitor liver function before initiation of treatment, then weekly for 1 month after initiation, then monthly for 6 months