Infectious disease 308 Flashcards
What are empirical antibiotics?
Best guess based on predicted pathogens
What are broad spectrum antibiotics?
Active against a wide range of pathogens
What are de-escalation antibiotics?
Refining antibiotic treatment based on microbiological results to narrowest spectrum possible
What factors must you consider when choosing an antimicrobial agent?
Infection
Patient
Drug
What infection factors must you consider when choosing an antimicrobial agent?
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
What patient factors must you consider when choosing an antimicrobial agent?
Penicillin allergy Pregnancy and breast feeding IV or oral route Medication history Renal/hepatic function Age Obesity Past medical history Severity of disease
What drug factors must you consider when choosing an antimicrobial agent?
Activity against likely pathogen Pharmacokinetic profile Dose Monotherapy vs combination Broad spectrum
What is cellulitis?
Diffuse, spreading superficial infection of the skin involving deep dermis and subcutaneous fat. No associated necrosis and does not involve muscle or fascia
Describe the clinical features of cellulitis
Heat Erythema Induration Tenderness Orange skin appearance Blisters/bullae Not raised and without well demarcated edge Systemic inflammatory response and regional lymphadenopathy
What are the causes of cellulitis
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
Name some beta lactamase sensitive penicillins
Benzylpenicillin (IV)
Phenoxymethylpenicillin (PO)
Name some broad spectrum penicillins
Amoxicillin
Co-amoxiclav
Name some beta lactamase resistant penicillins
Flucloxacillin
Name some anti-pseudomonal penicillins
Piperacillin
Tazobactam
What are the indications for penicillin use?
Streptococcal infection Exacerbation of COPD Pneumonia Cellulitis Endocarditis Ottis media Abdominal sepsis UTI
Describe the mode of action of penicillins
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
Which bacteria are penicillins not active against?
Mycoplasma
Chlamydia
Describe IgE mediated pencillin allergy (type 1 reactions)
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
What percentage of penicillin allergic patients will also be allergic to cephalosporins?
0.5-6.5%
If cephalosporin must be administered to a patient with IgE mediated penicillin allergy, which generations should be used?
2nd or 3rd
Which drugs should patients with IgE mediated penicillin allergy not be given due to cross reactivity?
Cephalosporins
Other beta lactams - meropenem
What questions must you ask if a patient reports penicillin allergy?
Seek the nature of the reaction
Timing post exposure
History of re-challenge and any consequences
Any skin testing
Name some aminoglycosides
Gentamicin
Amikacin
Tobramycin
Streptomycin
Describe the absorption of aminoglycosides
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
Describe the excretion of aminoglycosides
Kidney
What monitoring is required for aminoglycosides?
Serum levels
What are the risks of aminoglycosides?
Nephrotoxicity
Ototoxicity
Describe the mechanism of action of aminoglycosides
Bind to 30s subunit on bacterial ribosomes
Causes alteration in codon:anticodon recognition - misreading of the messenger RNA and production of defective bacterial proteins
Name some glycopeptides
Vancomycin
Teicoplanin
How are glycopeptides absorbed?
Given IV - not absorbed in the gut
How are glycopeptides excreted?
By the kidneys
What monitoring is required in glycopeptides?
Monitor serum levels
Trough level - aim 15-20mg
What is the loading dose of vancomycin based on?
Body weight
