A 73-year-old nursing home resident is seen by the staffing physician due to complaints of flank pain and bleeding upon urination for the past 2 days. Medical history includes hypertension, Alzheimer dementia, and recurrent episodes of pyelonephritis. In the past 3 months, she has received antibiotics on six different occasions to treat urinary tract infections. Her vitals are temperature 39° C (102.2° F), blood pressure 90/70 mmHg, heart rate 95 beats/min, and respirations 25/min. Urinary analysis shows 2+ blood, 3+ WBCs, 3+ bacteria and pH 8.2. Abdominal x-ray reveals a large radio-opaque structure that obstructs the renal pelvis and calyces.
Which of the following organisms is the most likely etiologic agent?
- A) Enterobacter aerogenes
- B) Escherichia coli
- C) Kelbsiella ozanae
- D) Proteus mirabilis
- E) Salmonella typhi
D) Proteus mirabilis
The patient’s urine is alkaline, indicating that the cause is an organism capable of raising the urinary pH. The organisms most often associated with such rises in pH, which can precipitate the formation of staghorn calculi as seen in this patient, are those that are urease positive. Proteus mirabilis is a urease-positive organisms which raises urine pH and is associated with the formation of staghorn calculi.
Key Learning Point
Proteus mirabilis is a urease-positive organisms which raises urine pH and is associated with the formation of staghorn calculi.