A 26-year-old non-pregnant woman presents with dysuria and urinary frequency for 2 days. She is afebrile, has no flank pain and no vaginal discharge. Urinalysis is positive for nitrites and leukocytes. She has no significant comorbidities and no drug allergies. According to Australian guidelines, which antibiotic is usually recommended as a first-line agent for acute uncomplicated cystitis?