Anaerobic susceptibility data – Australia and New Zealand and microLab comments

This posting summarises all the work that can be found – I would welcome advice about any additional studies.  Image: Bacteroides fragilis Gram stain from http://microbe-canvas.com/.

Australia

New Zealand

Microbiology reporting comments (Pathology North)

Mixed or Gram negative anaerobic isolate(s)

Antibiotics that are active against Gram negative and Gram positive anaerobes (mixed infections) include metronidazole (oral/IV, dose 12-hrly), lincomycin (IV), clindamycin (IV/oral), piperacillin+tazobactam (IV) or amoxicillin+clavulanate (oral). See Therapeutic Guidelines: Antibiotic Edition 14 for advice on doses.

Gram positive anaerobic isolate(s)

Benzylpenicillin (IV), amoxicillin (oral), di/flucloxacillin (IV/oral) at usual dosage are active against Gram positive anaerobes. Broader spectrum anaerobic agents such as metronidazole (IV/oral, dose 12-hrly), lincomycin (IV), clindamycin (IV/oral) or piperacillin+tazobactam (IV) are also active.

Metronidazole dosing

Metronidazole exhibits a concentration-dependent killing effect against anaerobes and has a post-antibiotic effect for more than 3 hours. Studies show that the metronidazole minimum inhibitory concentration (MIC) for most susceptible anaerobes is <6.2 micrograms/mL. Trough concentrations with 12-hourly dosing (400mg orally & 500mg IV) are in excess of the MICs for the majority of anaerobes. In Australia, 12-hrly dosing has been the routine for some years now and is recommended by Therapeutic Guidelines: Australia.

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