Empiric Antimicrobials used in Hospital

Emiric Antimicrobials in Hospital

Written by – Dr Andrew Lam

Penicillins

MoA: Beta lactam ring binds to Penicillin Binding Protein (PBP) on cell walls. As a result, they prevent cross-linking and cell wall synthesis leading to cell death

Benzylpenicillin – Narrow Spectrum: Streptococcus, Listeria, Syphilis

Flucloxacillin – MSSA

Addition of further beta lactam inhibitors helps to broaden spectrum of activity:

Amoxicillin + Clavulanate (Augmentin) 

Piperacillin + Tazobactam (Tazocin) 

Cephalosporins

MoA: As per penicillins, but altered beta lactam ring confers resistance to some beta lactamases

Cefazolin – Mostly gram positive cover, some gram negative cover -> used for skin infections and surgical skin prophylaxis

Ceftriaxone – Broad spectrum gram positive and negative cover -> used widely in respiratory tract, urine, and abdominal infections

Macrolides

MoA: Inhibits the production of proteins by binding to the 50s ribosomal subunit

Azithromycin – Gram positive and negative activity, but used primarily for its atypical coverage (i.e. legionella, mycoplasma) 

Nitroimidazoles

MoA: Damages bacterial cell DNA by promoting the formation of free radicals

Metronidazole – Strong activity against anaerobic bacteria

Gentamicin

MoA: Inhibits the production of proteins by binding to the 30s ribosomal subunit

Wide gram negative coverage

Vancomycin

MoA: Binds to the D-alanyl D-alanine site on the peptidoglycans of the cell wall to inhibit cell wall synthesis

Wide gram positive coverage. Utilised in treatment of MRSA, or used orally in C. Difficile colitis