Infectious disease formulatory teaching

Question 1

Empirical definition

Answer 1

Best guess

Based on predicted pathogens

Question 2

Broad spectrum definition

Answer 2

Active against a wide range of pathogens

Question 3

De-escalation definition

Answer 3

Refining antibiotic treatment based on microbiological results to narrowest spectrum possible

Question 4

Absorption

Answer 4

The uptake of drugs by the tissues of the body from the site of administration

Generally refers to absorption from the gastro-intestinal tract

Question 5

Distribution

Answer 5

The distribution of drugs to various parts of the body including site of action

Question 6

Metabolism

Answer 6

The breakdown of drugs by the body

Question 7

Excretion

Answer 7

The removal of waste products of metabolism or unchanged drug from the body

Question 8

Concentration dependent antibiotics

Answer 8

Bacterial effect related to peak concentration at site of infection

Continue to kill the bacteria until next dose given

e.g. aminoglycosides, quinolones

Question 9

Time dependent antibiotics

Answer 9

Bacterial effect dependent upon maintaining blood concentration above the minimum inhibitory concentration

Little or no post-antibacterial effect

e.g. penicillins, macrolides, glycopeptides

Question 10

Antibiotic targets in bacteria

Answer 10

Cell wall synthesis

DNA synthesis

RNA synthesis

Protein synthesis

Folic acid synthesis

Question 11

Antibiotics targeting cell wall synthesis

Answer 11

Penicillins

Cephalosporins

Carbapenems

Daptomycin

Glycopeptides

Question 12

Antibiotics targeting DNA synthesis

Answer 12

Fluoroquinolones

Question 13

Antibiotics targeting RNA synthesis

Answer 13

Rifampin

Question 14

Antibiotics targeting protein synthesis

Answer 14

Macrolides

Chloramphenicol

Tetracycline

Aminoglycosides

Oxazolidonones

Question 15

Antibiotics targeting folic acid synthesis

Answer 15

Sulfonamides

Trimethoprim

Question 16

Infection factors

Answer 16

Likely pathogen
- emprical vs targeted therapy

Resistance

• MRSA
• local resistance patterns

Site of infection

Severity

• local/ systemic
• septic shock
• toxin production

Question 17

Patient factors

Answer 17

Penicillin allergy

Pregnancy and breast feeding

IV or oral

Medication history

Renal/ hepatic function

Age

Obesity

PMH

Severity of disease

Question 18

Drug factors

Answer 18

Activity against likely pathogen

• mechanism of action
• resistance

Good penetration to site of infection

Dose

Monotherapy vs combination

Broad spectrum

Question 19

Cellulitis

Answer 19

Diffuse, spreading, superficial infection of skin

Without underlying suppurative foci in muscle or fascia

Without associated necrosis

Involves deeper dermis and subcutaneous fat

Treatment always required

Question 20

Characteristics of cellulitis

Answer 20

Heat, erythema, induration, localised tenderness, orange skin appearance

Blisters or bullae

Not raised and without a well demarcated edge

May have systemic inflammatory response and regional lymphadenopathy

Question 21

Causes of cellulitis

Answer 21

Infection following minor breach of skin

• insect bite
• tinea pedis

Question 22

Increased risk of cellulitis infection in

Answer 22

Immunocompromised

Following trauma/ surgery

Diabetes mellitus/ lymphoedema

Morbidly obese

Question 23

Bacteria to cause cellulitis

Answer 23

Group A streptococcus (strep pyogenes)

Staphylococcal aureus (MSSA and MRSA)

Other beta haemolytic streptococci

Dog/ cat bite (paseurella multicoda, capnocytophaga carnimorsus, human bite corridens)

Salt water exposure vibrio vulnificus

Question 24

Beta lactamase sensitive penicillins

Answer 24

Benzylpenicillin (IV)

Phenoxymethylpenicillin (PO)

Question 25

Broad spectrum penicillins

Answer 25

Amoxicillin

Co-amoziclav

Question 26

Beta-lactamase resistant penicillins

Answer 26

Flucloxicillin

Question 27

Anti-pseudomonal penicllins

Answer 27

Piperacillin

Tazobactam

Question 28

Indications for penicillins

Answer 28

Streptococcal infections

Exacerbations of COPD

Pneumonia

Cellulitis

Endocarditis

Otitis media

Abdominal sepsis

UTIs

Question 29

Penicillin mode of action

Answer 29

Bactericidal

Beta-lactam ring integrity crucial for antimicrobial activity

Activity against bacteria with PGN cell walls

Inhibit cell wall peptidoglycan synthesis

Question 30

Penicillin activity

Answer 30

Gram +ve, -ve, aerobes, anaerobes

Not chlamydia, mycoplasma

Question 31

IgE mediated pencillin allergy

Answer 31

Type 1 reaction

Sudden, life threatening, occurs up to 24 hours post exposure

Antigen and pre-formed IgE antibody cause histamine release

• anaphylaxis
• urticaria
• puritic rash
• laryngeal oedema
• angioedema
• bronchospasm

Question 32

Cross- sensitivity: cephalosporins

Answer 32

0.5-6.5% penicillin allergic patients also allergic to cephalosporins

Patients with IgE mediated reactions should not be given cephalosporins

Question 33

Cross- sensitivity: other beta lactam antibiotics

Answer 33

Namely carbapenems

e.g. meropenem

Question 34

IV -> oral switch

Answer 34

After 48 hours IV teicoplanin, patient is apyrexial, haemodynamically stable, cellulitis receeding, inflammaotry markers improving

Decision to discharge on oral antibiotics

Question 35

Aminoglycosides

Answer 35

e.g. gentamicin, amikacin, tobramycin, streptomycin

Not absorbed in the GI tract
- given IV/ IM

Polycations, highly polar

• do not cross blood brain barrier
• cross the placenta (avoid in pregnancy)
• concerns about lung tissue concentrations of gentamicin

Question 36

Excretion of aminoglycosides

Answer 36

Virtually entirely via kidenys

Consider alternative in renal impairment/ renal replacement

Monitoring serum levels

Dose related nephrotoxicity and ototoxicity

High risk antibiotic

Question 37

Glycopeptides

Answer 37

e.g. vancomycin, teicoplanin

Not absorbed from gut
- given IV

Excretion almost entirely via glomerular filtration into urine