The proposed endpoints of the study would be: comparative use of piperacillin versus broader spectrum agents (e.g., piperacillin/tazobactam, etc.) [measured as defined daily doses per 1000 patient days]; physician acceptance of piperacillin as part of a streamlining program [measured as successful occurrences of the use of piperacillin as streamlining therapy]; changes in susceptibility patterns of broad spectrum antibiotics [measured as % Gram negative bacilli susceptible to each of the commonly used broad spectrum antibiotics]; and outcome of patients treated with streamlined therapy.

The following variables will be followed: time and location of positive cultures, underlying diseases and severity of illness, recent immunomodulative therapies, physical exam findings, laboratory and radiographical data, antimicrobial usage, microbiological data and resistance patterns, choice of antibiotics once organism is identified, suspected source of infection, bacteriological outcomes, laboratory results, demographic information, medications, clinical outcome, gender, height, weight, ethnicity, and past medical history.

Inclusion Criteria:

• Patients with Gram negative infections treated with piperacillin/tazobactam and/or piperacillin

patients treated with piperacillin/tazobactam and or piperacillin