Do you recommend avoiding combination vancomycin and piperacillin-tazobactam in patients with acute kidney injury?  

Personally, I don't think the risk is that high and I won't necessarily recommend against it. If a patient develops worse renal function while on the drugs though, I would have a low threshold of switching to something different. I would also try to avoid vancomycin levels over 30. 

No, I think that is taking an association a bit too far for me. But I could easily be wrong.