Prevalence and characteristics of tigecycline- and carbapenem-resistant <i>adeN</i> -truncated <i>Acinetobacter baumannii</i> : a genomic epidemiological analysis

<i>adeN</i>-truncated <i>Acinetobacter baumannii</i> (ATAB) isolates are associated with elevated tigecycline resistance and enhanced virulence, yet its epidemic dynamics and genomic features remain poorly understood. This study aimed to investigate the epidemiology of ATAB isolates, identify infection risk factors, and assess their impact on patient prognosis. The prevalence of ATAB isolates in a tertiary care teaching hospital (Wenzhou, China) from January 2018 to December 2022 was determined via polymerase chain reaction (PCR) screening. Whole-genome sequencing and genomic analysis were conducted to explore the epidemiology and genomic characteristics of 254 ATAB isolates. Clinical data analysis was performed to identify risk factors for ATAB infection and its correlation with patient prognosis. The results of local sample analysis showed that <i>adeN</i> truncation was identified in 26.5% (486/1834) of the patient isolates, with the monthly prevalence peaking at 64.9% (24/37). The capsular types of ATAB isolates were primarily KL2, whereas <i>adeN</i>-complete isolates exhibited a greater capsular diversity. ATAB could evolve within the hospital and lead to multiple nosocomial clonal transmissions. Most ATAB isolates exhibited co-resistance to carbapenems and tigecycline. ICU admission and use of immunosuppressants were significant risk factors for ATAB isolate infection. Patients infected with ATAB isolates had significantly higher 28-day all-cause mortality (32.8%, 20/61) compared to those infected with <i>adeN</i>-complete isolates (11.5%, 7/61, <i>P</i> < 0.01). Bioinformatics analysis of the 18,946 completed and draft <i>A. baumannii</i> genome assemblies from the GenBank database showed that ATAB isolates were widely prevalent worldwide. This study highlights the importance of early identification and monitoring of ATAB isolates as a critical marker for hospital infection control.