ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Antimicrobials, Resistance and Chemotherapy
Volume 16 - 2025 | doi: 10.3389/fmicb.2025.1646319
This article is part of the Research TopicEfflux Pump-mediated Antimicrobial Resistance: Mechanisms, Clinical Impact, and Emerging Inhibitory ApproachesView all articles
Molecular Characterization of Carbapenem-Resistant and Carbapenem-Sensitive Acinetobacter baumannii Isolates from an Intensive Care Unit in Ningbo, China
Provisionally accepted
- Ningbo Medical Centre Lihuili Hospital, Ningbo, China
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This study aims to examine the variations in resistance genes, virulence genes, and drug susceptibility between carbapenem-resistant and carbapenem-susceptible Acinetobacter baumannii (CR-AB and CS-AB). Additionally, it seeks to assess the influence of efflux pump inhibitors on drug susceptibility, in order to provide new antimicrobial treatment strategies for CR-AB infections in the intensive care unit (ICU). Methods: A retrospective study was undertaken involving 39 Acinetobacter baumannii (A. baumannii) strains isolated from the ICU of Li Huili Hospital, affiliated with Ningbo University, during the period from January to December 2023. Of these strains, 18 were classified as CR-AB and 21 as CS-AB. The minimum inhibitory concentrations (MICs) of commonly employed clinical antibiotics, polymyxin B, tigecycline, and ceftazidime/avibactam, were assessed using the microdilution method. The alterations in MICs of ceftazidime/avibactam for CR-AB isolates were evaluated before and after the incorporation of the efflux pump inhibitor phenylalanine-arginine-βnaphthylamine (PAβN). Whole genome sequencing (WGS) was conducted to elucidate the differences in resistance and virulence genes, and phenotypic validation of these virulence gene differences was performed utilizing the Galleria mellonella larvae model.The CR-AB isolates demonstrated substantial resistance to ceftazidime, cefepime, ceftriaxone, ampicillin/sulbactam, tobramycin, gentamicin, and levofloxacin, while exhibiting moderate resistance to trimethoprim-sulfamethoxazole and amikacin. Conversely, the CS-AB isolates remained susceptible to all the aforementioned commonly utilized clinical antibiotics. Antimicrobial susceptibility testing indicated that 2.56% of the 39 A. baumannii strains displayed resistance to polymyxin B, with no resistance detected against tigecycline. PAβN was observed to reduce the MIC values of ceftazidime/avibactam against CR-AB in a concentrationdependent manner. Relative to the CS-AB isolates, the CR-AB isolates not only exhibited a more complex resistance gene profile but also showed greater diversity and abundance in their virulence gene profiles. The survival rate of CR-AB isolates was significantly lower in the Galleria mellonella larvae model, indicating that CR-AB strains from the ICU in Ningbo have evolved towards increased virulence and resistance.The CR-AB isolates from the ICU in Ningbo demonstrate heightened resistance and virulence traits in comparison to the CS-AB isolates. The application of the efflux pump inhibitor PAβN markedly increases the susceptibility of CR-AB to ceftazidime/avibactam.
Keywords: Carbapenem-resistant Acinetobacter baumannii, Intensive Care Unit, efflux pump inhibitor, virulence genes, Resistance genes
Received: 13 Jun 2025; Accepted: 12 Aug 2025.
Copyright: © 2025 Chen, Tu, Wang, Li, Zhao, Jiang, Gao and Zhang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Yanye Tu, Ningbo Medical Centre Lihuili Hospital, Ningbo, China
Feng Wang, Ningbo Medical Centre Lihuili Hospital, Ningbo, China
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