A 48-year-old man with a kidney transplant, stable on tacrolimus, mycophenolate mofetil and prednisolone, is treated by his general practitioner for a chest infection. A week later he has a coarse tremor, potassium 6.1 mmol/L and a creatinine that has risen from 110 to 205 µmol/L.
Which antibiotic is most likely to be responsible?