Infectious disease 308

Question 1

What are empirical antibiotics?

Answer 1

Best guess based on predicted pathogens

Question 2

What are broad spectrum antibiotics?

Answer 2

Active against a wide range of pathogens

Question 3

What are de-escalation antibiotics?

Answer 3

Refining antibiotic treatment based on microbiological results to narrowest spectrum possible

Question 4

What factors must you consider when choosing an antimicrobial agent?

Answer 4

Infection
Patient
Drug

Question 5

What infection factors must you consider when choosing an antimicrobial agent?

Answer 5

Likely pathogen - empirical or targeted therapy

Resistance- MRSA, local resistance patterns, recent antibiotic use, MIC of causative organism

Site of infection

Severity - local or systemic

Question 6

What patient factors must you consider when choosing an antimicrobial agent?

Answer 6

Penicillin allergy 
Pregnancy and breast feeding 
IV or oral route 
Medication history 
Renal/hepatic function 
Age
Obesity 
Past medical history
Severity of disease

Question 7

What drug factors must you consider when choosing an antimicrobial agent?

Answer 7

Activity against likely pathogen
Pharmacokinetic profile 
Dose
Monotherapy vs combination 
Broad spectrum

Question 8

What is cellulitis?

Answer 8

Diffuse, spreading superficial infection of the skin involving deep dermis and subcutaneous fat. No associated necrosis and does not involve muscle or fascia

Question 9

Describe the clinical features of cellulitis

Answer 9

Heat
Erythema 
Induration
Tenderness
Orange skin appearance
Blisters/bullae 
Not raised and without well demarcated edge 
Systemic inflammatory response and regional lymphadenopathy

Question 10

What are the causes of cellulitis

Answer 10

Minor breach of skin following insect bites or trauma
Infection risk increased in immunocompromised, DM, morbidly obese, trauma and surgery

Group A streptococci - Streptococci pyogenes
Staphylococcus aureus
Beta haemolytic streptococci - B, C, G
Dog/cat bite pasteurella multocida, capnocytophaga carnimorus, human bite eikonella corridens
Salt water exposure vibrio vulnificus

Question 11

Name some beta lactamase sensitive penicillins

Answer 11

Benzylpenicillin (IV)

Phenoxymethylpenicillin (PO)

Question 12

Name some broad spectrum penicillins

Answer 12

Amoxicillin

Co-amoxiclav

Question 13

Name some beta lactamase resistant penicillins

Answer 13

Flucloxacillin

Question 14

Name some anti-pseudomonal penicillins

Answer 14

Piperacillin

Tazobactam

Question 15

What are the indications for penicillin use?

Answer 15

Streptococcal infection 
Exacerbation of COPD 
Pneumonia
Cellulitis
Endocarditis 
Ottis media
Abdominal sepsis
UTI

Question 16

Describe the mode of action of penicillins

Answer 16

Bactericidal
Beta lactam ring crucial for antimicrobial activity
Active against bacteria with peptidoglycan cell walls as they inhibit synthesis of peptidoglycan cell walls
Gram positive, gram negative, aerobes, anaerobes

Question 17

Which bacteria are penicillins not active against?

Answer 17

Mycoplasma

Chlamydia

Question 18

Describe IgE mediated pencillin allergy (type 1 reactions)

Answer 18

Sudden, life threatening, occurs up to 24hrs post exposure - usually within 1 hour
Antigen and pre-formed IgE antibodies cause histamine release

• Anaphylaxis
• Urticaria
• Pruritic rash immediately following penicillin exposure
• laryngeal oedema
• Angioedema
• Bronchospasm

Question 19

What percentage of penicillin allergic patients will also be allergic to cephalosporins?

Answer 19

0.5-6.5%

Question 20

If cephalosporin must be administered to a patient with IgE mediated penicillin allergy, which generations should be used?

Answer 20

2nd or 3rd

Question 21

Which drugs should patients with IgE mediated penicillin allergy not be given due to cross reactivity?

Answer 21

Cephalosporins

Other beta lactams - meropenem

Question 22

What questions must you ask if a patient reports penicillin allergy?

Answer 22

Seek the nature of the reaction
Timing post exposure
History of re-challenge and any consequences
Any skin testing

Question 23

Name some aminoglycosides

Answer 23

Gentamicin
Amikacin
Tobramycin
Streptomycin

Question 24

Describe the absorption of aminoglycosides

Answer 24

Not absorbed in the GI tract - given IM/IV

Polycations/highly polar
Do not cross blood brain barrier or penetrate vitreous humour of the eye
Cross the placenta - avoid in pregnancy
Concerns about accumulation of gentamicin in the lung - avoid as 1st line in pneumonia

Question 25

Describe the excretion of aminoglycosides

Answer 25

Kidney

Question 26

What monitoring is required for aminoglycosides?

Answer 26

Serum levels

Question 27

What are the risks of aminoglycosides?

Answer 27

Nephrotoxicity

Ototoxicity

Question 28

Describe the mechanism of action of aminoglycosides

Answer 28

Bind to 30s subunit on bacterial ribosomes
Causes alteration in codon:anticodon recognition - misreading of the messenger RNA and production of defective bacterial proteins

Question 29

Name some glycopeptides

Answer 29

Vancomycin

Teicoplanin

Question 30

How are glycopeptides absorbed?

Answer 30

Given IV - not absorbed in the gut

Question 31

How are glycopeptides excreted?

Answer 31

By the kidneys

Question 32

What monitoring is required in glycopeptides?

Answer 32

Monitor serum levels

Trough level - aim 15-20mg

Question 33

What is the loading dose of vancomycin based on?

Answer 33

Body weight