The purpose of this pilot study is to assess the impact of an antibiotic de-escalation strategy on the clinical outcomes (clinical cure or improvement) of medical patients related to the usage of of broad-spectrum antimicrobial agents.

This is an open-label, case-control, pilot study involving medical patients with serious infections who are prescribed meropenem or piperacillin/tazobactam, at Surrey Memorial Hospital. Patients in the experimental arm (cases) will be required to provide an informed consent. A team consisting of an infectious diseases specialist, medical microbiologist and clinical pharmacists will prospectively assess antimicrobial therapy in the enrolled subjects in the prospective arm and make recommendations for antimicrobial de-escalation.

The control group will consist of subjects drawn from historic data of patients on the same medical unit(s) who will be matched based on age, sex, use of broadspectrum antibiotics (meropenem or piperacillin/tazobactam) and infectious diseases diagnosis.

Inclusion Criteria:

• Age 19 years and over
• Suspected or confirmed infection for which a Meropenem and/or Piperacillin/Tazobactam is prescribed. This will include any patient who is other concomitant antibiotic(s) such as Vancomycin
• Subject admitted to SMH medical unit(s)
• Pregnant patient (or patients wishing to become pregnant)

Exclusion Criteria:

• Age less than 19 years
• Granulocytopenia (< 1x109/L)
• Allergy or intolerance to meropenem or piperacillin-tazobactam.
• Febrile Neutropenia
• Cystic Fibrosis