You are risking your life asking us! I suggest Medscape, which is up-to-date, peer-reviewed and authoritative. 

Whyyou are afraid  dear Ronan? It is a  way of exchange knowlege. Previously it is third generation cephalosporin and amikacin but now tazobactum use.I like to know practical experience which is beter.

Agreed to the suggestion by Ronan as the options could be many. Moreover evidence may found different from the standards of practice, which requires familiarization with local guidelines. Not to forget you may refer to IDSA guidelines or any other updated data base, however Medscape (e-medicine) is often driven by the mentioned.

All the best.

Vancomycin IV per pharmacy consult (initial 25mg/kg loading dose). Piperacillin/tazobactam 4.5g IV q8h, infused over 4 hours OR

Cefepime 1 gm IV q6hr +/- Tobramycin 7 mg/kg IV EIAD

It is really difficult to give recommendations without know what is your local bugs ecology a your antibiotics resistance profile, so maybe the best is to follow standard recommendations that are publishing in many journal. (IDSA guidelines p.e)

I think Medscape is so helpful (link below)

http://emedicine.medscape.com/article/234587-treatment

Thank you.