Medicine Which of the following is the most common cause of acute pyelonephritis in patients without Urological abnormalities or urinary calculi? A Pseudomonas aeruginosa B Proteus mirabilis C Escherichia coli D Serratia marcescens 💡 Explanation Which of the following is the most common cause of acute pyelonephritis in patients without Urological abnormalities or urinary calculi? ✓ Correct Answer: C. Escherichia coli