Bacterial Treatments at a glance
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Please note that microbial sensitivities vary between regions & countries, as well as over time. Individual hospital guidelines very widely, and this is just an overview of general sensitivies. Please check your local hospital guidelines for specific advice when prescribing.

Gram positive


Catalase positive – Staphylococcus
  • S. aureus – flucloxacillin
  • S. saprophyticus – Penicillin
  • S. epidermidis – Vancomycin
Catalase negative – Streptococcus
  • Group A B-haemolytic strep: S. pyogenes
  • GBS – agalactiae
  • Alpha-haemolytic – S. viridians and S. pneumoniae
  • Gamma-haemolytic – enteroccus
  • Treat all above with penicillin


  • Clostridium – metronidazole, vancomycin
  • Listeria – ampicillin, ceftriaxone, cotrimoxazole
  • Bacillus: anthracis – penicillin, doxycycline, ciprofloxacin, levofloxacin
  • Bacillus: cereus – no antibiotics
  • Corynebacterium diptheriae – penicillin, erythromycin

Gram Negatives


  • Haemophilus influenza – serious (cefotaxime/ceftriaxone) less serious (ampicillin/amoxicillin)
  • Brucella – tetracyclines, rifampicin, aminoglycosides
  • Legionella – erythromycin + rifampicin
  • Pertussis – erythromycin in early stage
  • Diplococci
  • Neisseria meningitidis – ceftriaxone/penicillin G (close contacts Rifampicin)
  • Neisseria gonorrhoeae – ceftriaxone


Lactose positive
  • E. coli – avoid abx
  • Enterobacter
  • Klebsiella –3rd generation cephalosporin
Lactose negative
  • Bacteriodes fragilis – ceftriaxone
Lactose negative oxidase positive
  • Vibrio cholera
  • Pseudomonas – Pitazobactam or ciprofloxacin + gentamycin
  • Campylobacter – fluoroquinolones/erythromycin
Lactose negative oxidase negative
  • H. pylori – PPI + amoxicillin + clarythromycin
  • Shigella – fluoroquinolones
  • Salmonella – ciprofloxacin/ceftriaxone
  • Yersinia – no antibiotics

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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