My dad, 90yrs old has been hospitalized for influenza B. He was getting better and now all of a sudden got delusional and talking incoherently. This happened to him before and tests were run and MRI he does not have dementia or Alzheimers. Doc said it was the antibiotic causing this. This time he was given another antibiotic and did well the first week at hospital. Now he is delusional again. Could it be the antibiotic again?