LAUSR

Pseudomonas aeruginosa is an opportunistic Gram-negative bacillus that causes serious infections. This pathogen has several intrinsic resistance mechanisms that can result in multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains [1]. As a result, infections due to P. aeruginosa are often challenging to treat. P. aeruginosa infective endocarditis (IE) which is rare, accounting for < 0.5% of all endocarditis cases [2]. Historically, P. aeruginosa IE had been associated with intravenous drug use; nevertheless, the rising incidence in recent years has been related to healthcare associated infections. Thus, P. aeruginosa IE has been observed in patients with pacemaker or prosthetic valve, and in those with immunosuppressive therapy or genitourinary manipulations [2]. Ceftazidime–avibactam (CAZ-AVI) has been used for treatment of serious infections due to MDR and XDR P. aeruginosa, without documented resistance emergence [3]. There are no data about CAZ-AVI use in IE in adults. A 72-year-old male presented to the emergency department with hypotension, stupor, and fever. One month earlier, he had undergone a radical cystoprostatectomy, lymphadenectomy and Bricker-type urinary diversion because of a pT3N1Mx urothelial carcinoma. He had no pacemaker or prosthetic valves. On admission, the patient had clinical and analytical data of sepsis, so intravenous meropenem (1 g q 8 h) was initiated. Twenty-four hours after admission, a non-fermentative Gram-negative bacillus was isolated in blood and urine cultures. The isolate was identified as P. aeruginosa by Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS, Bruker Daltonik GmbH) and was analysed for antimicrobial susceptibility using MicroScan Walk-Away® system (Beckman Coulter Inc.), and the results were interpreted according to EUCAST breakpoints (antibiotic susceptibility profile is shown in Fig. 1), so meropenem was de-escalated to ceftazidime, in extended infusion (2 g q 8 h). On physical examination, an unknown systolic murmur was detected, so a transthoracic echocardiogram was performed, showing an aortic valve sclerosis and grade II/IV aortic regurgitation, without suggestive data of endocarditis. Twelve days after admission, the patient presented a new episode of fever and hypotension. Once again, P. aeruginosa with a different susceptibility pattern (Fig. 1) was detected in blood cultures; therefore, meropenem (extended infusion of 1 g q 8 h) was initiated. Forty-eight hours later, in new blood cultures grew MDR P. aeruginosa (Fig. 1). Given the worldwide shortage of ceftolozane–tazobactam during 2021, ceftazidime–avibactam (2000 mg ceftazidime plus 500 mg avibactam 2-h IV infusions every 8 h) plus amikacin (20 mg/kg/24 h), were started. After 2 weeks, amikacin was suspended, maintaining ceftazidime–avibactam in monotherapy. All the following blood cultures were negative. A thorax-abdominal computed tomography (CT) scan did not show abscess. Due to the high suspicion of the endovascular source of infection, a transoesophageal echocardiography (TEE) was requested, but showed no lesions. Four weeks later, a second TEE revealed a severe aortic regurgitation and vegetation on the * Olalla Lima [email protected]