Empiric regimens should be made based on

1. The organisms identified earlier in the patient in the previous 6 months and their anti- microbial susceptibility
2. The antimicrobial exposure  in the previous 30 days, and
3. Local antibiogram

For hospital acquired organisms like carbapenem resistant Acinetobacter and S. maltophila distinction should be made between bacterial colonization and true infection and because in general, empiric regimens do not target these organisms, any decision to treat must be made after careful evaluation of the risk versus benefit of therapy.