Case Presentation: A 56-year-old female with history of tobacco use, chronic obstructive pulmonary disease, and chronic alcoholic pancreatitis presented to the hospital with 5 days of fever, left flank pain, and dysuria. Vitals were notable for tachycardia. On physical exam, there was moderate tenderness on palpation of her left flank. Blood tests were significant for lactic acidosis, leukocytosis, elevated creatinine 2.4, and metabolic acidosis with HCO3 11. Urinalysis was concerning for a urinary tract infection. Patient was started on broad spectrum antibiotics and underwent CT imaging which revealed a left sided renal calculus, hydronephrosis, hydroureter, and gas in the left collecting system, findings consistent with class 1 emphysematous pyelonephritis. Hospital course was complicated by severe septic shock, cardiac arrest, and acute hypoxic respiratory failure. A left percutaneous nephrostomy tube was emergently placed. Urine culture from the nephrostomy tube as well as blood cultures were positive for Raoultella ornithinolytica resistant to ampicillin but sensitive to ceftriaxone. Patient was treated with a 2-week course of ceftriaxone and gradually improved. She was discharged to home with urology follow-up for left percutaneous nephrolithotomy.
Discussion: Raoultella ornithinolytica belongs to the family Enterobacteriaceae and is a gram-negative, non-motile, encapsulated, aerobic bacillus formerly named Klebsiella ornithinolytica. It is commonly found in fish, water, and soil. It has been known to cause scombroid syndrome, which occurs after ingestion of fish with high histamine levels due to improper processing or storage. Scombroid syndrome manifests with facial flushing, dizziness, headache, palpitations, vomiting, and diarrhea. R. ornithinolytica is an emerging hospital-acquired infection that affects mostly patients with a weakened immune system and/or significant comorbidities such as diabetes mellitus and chronic kidney disease. A significant amount of infections by this organism are simple urinary tract infections and respiratory infections; only a few cases of complicated urinary tract infection have been reported.
Conclusions: Emphysematous pyelonephritis mostly occurs in patients with diabetes mellitus but can be seen in patients without diabetes mellitus who have urinary tract obstruction. Common causes include E. coli, K. pneumonia, and P. mirabilis. The organism R. ornithinolytica is known to be underreported due to the difficulty of identification by conventional phenotypic methods. The virulence of R. ornithinolytica is becoming more important with the increasing amount of hospital-acquired infection caused by this pathogen. It has the ability to adhere to human tissue, form biofilms in urinary catheters, and to convert histidine to histamine. In addition, it expresses β-lactamase, which provides resistance to ampicillin. This case is an example of Raoultella ornithinolytica emerging as a causative agent of a wide variety of life-threatening clinical presentations.