mrcem2-2153

A 30-year-old woman on treatment for a urinary tract infection returns after 48 hours because her symptoms have not improved. She is currently 20 weeks pregnant. Unfortunately, the sensitivities from the urine sample that was sent to the lab are still unavailable. Her blood tests today show that her eGFR is >60 ml/minute. She has been taking nitrofurantoin 100 mg modified-release PO BD for the past two days.
Which of the following antibiotics is the most suitable to prescribe in this situation?