E. coli and Enterobacteriaceae

A 28-year-old woman from Delhi presents to the emergency department with acute onset dysuria, frequency, and suprapubic pain for 2 days. She denies fever, flank pain, or vaginal discharge. Urinalysis shows pyuria (>5 WBC/hpf), bacteriuria, and nitrites. Urine culture is pending. Blood pressure is 110/70 mmHg, temperature 37.2°C. She has no known drug allergies. Which of the following is the most appropriate empiric antibiotic choice for uncomplicated acute cystitis in this patient?

A 28-year-old woman presents with acute cystitis caused by uropathogenic E. coli (UPEC). Urine culture confirms the organism; susceptibility testing shows sensitivity to all first-line agents. What is the drug of choice for uncomplicated acute cystitis due to E. coli in non-pregnant women?

A 52-year-old man with type 2 diabetes mellitus presents with a 3-day history of fever (39.2°C), right flank pain, and dysuria. Urinalysis shows pyuria, bacteriuria, and positive leukocyte esterase. Blood cultures and urine culture both grow a gram-negative rod that is oxidase-negative, non-motile, and produces a mucoid colony morphology on blood agar. The organism is negative for indole and methyl red but positive for Voges-Proskauer test. What is the most likely causative organism?

A 45-year-old man with diabetes and recurrent urinary tract infections presents with fever, flank pain, and dysuria. Urine culture yields a lactose-fermenting, oxidase-negative organism. Gram stain shows Gram-negative rods. The organism is positive for indole, methyl red, and negative for Voges-Proskauer. Which is the most appropriate next investigation to confirm uropathogenic E. coli (UPEC) and guide antibiotic selection?

A 65-year-old man with diabetes mellitus type 2 and benign prostatic hyperplasia presents with fever (38.9°C), dysuria, and left flank pain. Urine culture grows E. coli resistant to fluoroquinolones but susceptible to cephalosporins and carbapenems. Blood cultures are pending. Serum creatinine is 1.8 mg/dL (baseline 1.2 mg/dL). What is the most appropriate next step in management?