Clinical and Microbiological Profile of Ceftazidime-Avibactam-Resistant Isolates in a Tertiary Hospital in Porto Alegre

Ceftazidime-avibactam (CAZ-AVI) is one of the main therapeutic options for infections caused by multidrug-resistant Gram-negative bacilli, especially KPC-producing Enterobacterales. However, the emergence of resistance to this antimicrobial is a growing and concerning phenomenon. The objective of this study is to describe the clinical profile of cases with isolation of CAZ-AVI-resistant microorganisms in a tertiary, private hospital in Porto Alegre, RS. Exploratory and retrospective study including all patients with bacterial isolates resistant to CAZ-AVI (only one isolate per patient) identified between January and June 2025. Bacterial identification was performed by MALDI-TOF (bioMérieux), and susceptibility testing followed BrCAST guidelines. Carbapenemase identification was performed with a lateral flow test (NG-Test® CARBA-5 - Biotech). Clinical data and 30-day outcomes were evaluated. During the period, 97 KPC-producing isolates were identified, 19 of which showed resistance to CAZ-AVI. These isolates came from 16 patients, three of whom had a new positive isolate during hospitalization. Most patients were male (12; 75%), with a median age of 74 years (range: 34–94). Active infections caused by KPC-producing Gram-negative bacilli were identified in 12 patients. Previous KPC-positive cultures were documented in 9 patients (56%), and 4 (25%) had used CAZ-AVI during hospitalization. Microbiologically, most isolates (16; 84%) were Klebsiella pneumoniae , followed by Proteus mirabilis (1) and Pseudomonas putida (1). The co-production of carbapenemases was the main mechanism identified, with NDM detected in 9 isolates (56%) and VIM in 1 isolate. Regarding infection sites: respiratory tract (5; 31%), abdominal (3; 19%), urinary (3; 19%), and blood (2; 13%). In terms of outcomes, 7 patients (44%) died within 30 days after the culture. The identification of multiple CAZ-AVI-resistant cases in a short time interval reflects a scenario of local emergence of resistance. The high frequency of carbapenemase co-production, especially KPC+NDM, associated with severe infections and high mortality, reinforces the need for active surveillance, infection control measures, and rational antimicrobial use strategies.