P-290. Clinical and microbiological characteristics of patients infected with ceftazidime/avibactam-resistant <i>Klebsiella pneumoniae</i> carbapenemase-producing <i>K. pneumoniae</i> strains

Abstract Background Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae with ceftazidime/avibactam (CZA) resistance emerged after the widely use of CZA. The most common resistance mechanism was mutations in blaKPC. We aimed to study the clinical and microbiological characteristics in patients infected with CZA-resistant KPC-producing K. pneumoniae, and focus on the comparison between the strains with or without KPC variants (wild-type KPC). Methods A retrospective study was conducted in Taipei Veterans General Hospital from February 2019 to July 2023. Hospitalized unique adult patients infected with CZA-resistant KPC-producing K. pneumoniae were included. Clinical characteristics and outcomes were collected, and genes encoding carbapenemases were detected by polymerase chain reaction followed by Sanger sequencing. Results A total of 44 cases with CZA-resistant KPC-producing K. pneumoniae infections were identified, and most of them were critically ill with the median APACHE II score 23.0 (IQR, 19.3-29.8). Pneumonia was the most common infection (n=18). Only 15 patients (34.1%) received appropriate treatment regimens, and tigecycline (n=8) and meropenem-based therapy (n=5) were the common regimens. Twenty-seven strains (61.4%) harbored KPC variants, and a total of 16 different types were identified. KPC-33 (n=10) was the most common, followed by KPC-35 (n=3). The overall 28-day mortality was similar between patients infected with and without KPC variants (22.2% vs 23.5%, p=1.000). A previous isolation of carbapenem-resistant K. pneumoniae and exposure to CZA were more common in KPC variants group compared with wild-type KPC group (92.6% vs 58.8%, p=0.017, 92.6% vs 41.2%, p&amp;lt; 0.001, respectively). KPC variants-producing strains also had a higher proportion of CZA MIC &amp;gt; 16 mg/L (85.2% vs 41.2%, p=0.002) and restored meropenem susceptibility (MIC≤ 4 mg/L) (70.4% vs 5.9%, p&amp;lt; 0.001) than that in wild-type KPC strain. Conclusion CZA-resistant KPC variants-producing K. pneumoniae has the tendency of restored meropenem susceptibility and higher level of CZA resistance compared with the wild type KPC-producing strain. The optimal therapy in these patients needs further study. Disclosures All Authors: No reported disclosures