After the Lithotripsy
Clinical Vignette
A 59-year-old man with traumatic spinal cord injury, neurogenic bladder managed with intermittent catheterization, type 2 diabetes, and recurrent nephrolithiasis is admitted with fever, rigors, and hypotension 24 hours after ureteroscopy with laser lithotripsy and left ureteral stent placement for an obstructing ureteral stone. During the preceding 3 months he had repeated urinary symptoms treated with trimethoprim-sulfamethoxazole, ciprofloxacin, and, during a prior hospitalization, piperacillin-tazobactam. A pre-procedural urine culture later returned with Pseudomonas aeruginosa, and he received peri-procedural cefepime.
On arrival, temperature is 39.1 C, heart rate 118/min, blood pressure 88/54 mmHg, respiratory rate 24/min, and oxygen saturation 96% on room air. He has left flank tenderness and appears toxic but is alert. Laboratory studies show white blood cells 16.9 x 10^3/uL, creatinine 1.8 mg/dL from a baseline of 1.0 mg/dL, lactate 3.1 mmol/L, and C-reactive protein 241 mg/L. CT of the abdomen and pelvis shows residual stone fragments, the ureteral stent in place, persistent mild hydronephrosis, and bladder wall thickening.
Blood cultures and urine cultures both grow Pseudomonas aeruginosa. Gram stain from a culture-positive specimen shows gram-negative bacilli. Final susceptibility testing demonstrates resistance to ciprofloxacin, levofloxacin, piperacillin-tazobactam, ceftazidime, cefepime, aztreonam, meropenem, and imipenem, with retained susceptibility to amikacin, ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam, and cefiderocol.
Gram stain demonstrating gram-negative bacilli from a culture-positive specimen. Morphology supports a gram-negative rod infection but does not establish species identity without culture-based identification.
Question 1
Which is the best definitive antimicrobial therapy once susceptibilities are known and source control is being pursued?
Select one option to submit your answer and view live poll results.
Question 2
Which resistance mechanism best explains this susceptibility pattern?
Select one option to submit your answer and view live poll results.
Question 3
Beyond choosing an active antibiotic, what is the most important management principle in this case?
Select one option to submit your answer and view live poll results.
References
Tamma PD, Heil EL, Justo JA, Mathers AJ, Satlin MJ, Bonomo RA. IDSA 2024 guidance on the treatment of antimicrobial resistant Gram-negative infections. Clin Infect Dis. 2024;ciae403.
Kadri SS, Adjemian J, Lai YL, et al. Difficult-to-treat resistance in Gram-negative bacteremia at 173 US hospitals: retrospective cohort analysis of prevalence, predictors, and outcome of resistance to all first-line agents. Clin Infect Dis. 2018;67(12):1803-1814.
Karlowsky JA, Lob SH, DeRyke CA, et al. In vitro activity of ceftolozane-tazobactam, imipenem-relebactam, ceftazidime-avibactam, and comparators against Pseudomonas aeruginosa isolates collected in United States hospitals according to results from the SMART surveillance program, 2018 to 2020. Antimicrob Agents Chemother. 2022;66(5):e0018922.
Almangour TA, Ghonem L, Alassiri D, et al. Ceftolozane-tazobactam versus ceftazidime-avibactam for the treatment of infections caused by multidrug-resistant Pseudomonas aeruginosa: a multicenter cohort study. Antimicrob Agents Chemother. 2023;67(8):e0040523.
Hareza DA, Cosgrove SE, Bonomo RA, et al. Clinical outcomes and emergence of resistance of Pseudomonas aeruginosa infections treated with ceftolozane-tazobactam versus ceftazidime-avibactam. Antimicrob Agents Chemother. 2024;68(10):e0090724.
Shields RK, Abbo LM, Ackley R, et al. Effectiveness of ceftazidime-avibactam versus ceftolozane-tazobactam for multidrug-resistant Pseudomonas aeruginosa infections in the USA (CACTUS): a multicentre, retrospective, observational study. Lancet Infect Dis. 2025;25(5):574-584.
Shah S, Kline EG, Haidar G, et al. Rates of resistance to ceftazidime-avibactam and ceftolozane-tazobactam among patients treated for multidrug-resistant Pseudomonas aeruginosa bacteremia or pneumonia. Clin Infect Dis. 2025;80(1):24-28.