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Volume 12, Issue 4

Comparative genomic and resistance characterization of ST2 and ST164 carbapenem-resistant from hospital environments and clinical specimens Open Access

Abstract

Carbapenem-resistant (CRAB) represents a formidable nosocomial pathogen, with healthcare environments acting as critical reservoirs for its dissemination. In this study, we investigated the prevalence, antimicrobial resistance profiles and genomic characteristics of CRAB isolates collected from hospitals in Shanghai, China, between June and December 2024, identifying ST2 (84.13%) and ST164 (15.08%) as the predominant lineages among the 126 CRAB isolates recovered from clinical (=94), environmental (=29) and healthcare worker (=3) sources. Environmental CRAB accounted for the highest proportions on patient-contact surfaces (34.48%), medical devices (31.03%) and shared items (24.14%). Within the dominant ST2 lineage, clinical isolates exhibited higher resistance rates to ampicillin/sulbactam, cefoperazone/sulbactam and levofloxacin, with significantly higher carriage rates of compared to environmental isolates. Compared to ST164, ST2 CRAB isolates exhibited greater resistance to amikacin, gentamicin, trimethoprim/sulfamethoxazole and minocycline and a higher prevalence of (3′)-Ia, (3″)-Ib, )-VI, (6)-Id, A, , (E) and (B), but lower rates of , and (0.05). Notably, comparative genomic analysis suggested putative adaptive differences between the two lineages. ST2 retained the T6SS and biofilm-associated genes (), descriptive genomic features that suggest a potential capacity for active colonization. Conversely, the ST164 clone lacked the T6SS gene cluster but was enriched with the surface adhesin and immune evasion-related genes. Concordantly, ST164 CRAB isolates exhibited significantly stronger biofilm-forming capacities than ST2 . We hypothesize that these genomic alterations and phenotypic traits may represent a fitness trade-off, potentially conferring a survival advantage under antibiotic pressure. Furthermore, in ST2 was predominantly carried on conjugative plasmids restricted to species, whereas in ST164 was localized on a broad-host-range non-mobile plasmid, potentially facilitating cross-genus transmission. Although our ST164 isolates shared high homology with clinical strains from Zhejiang, China, the genomic localization of differed between the plasmid and chromosome, respectively. These descriptive genomic findings highlight the putative adaptive trajectories of the predominant ST2 and emerging ST164 clones, underscoring the critical need for comprehensive genomic surveillance, complemented by future phenotypic validation, to monitor their rapid evolution and dissemination.

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  • Accepted:
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Keyword(s): antimicrobial resistance , carbapenem-resistant Acinetobacter baumannii , ST164 , ST2 and whole-genome sequencing
Funding
This study was supported by the:
  • the Medical Discipline Construction Program of Shanghai Pudong New Area Health Commission (Award PWGw2025-05)
    • Principal Award Recipient: YuanpingWang
  • The Young Medical Talents Training Program of Shanghai Pudong New Area Health Commission (Award PWRq2025-03)
    • Principal Award Recipient: XiaoWang
  • The Project of Shanghai Pudong New Area Center for Disease Control and Prevention (Award PDCDC-KJ-2024-19)
    • Principal Award Recipient: TongshengXu
© 2026 The Authors
  • This is an open-access article distributed under the terms of the Creative Commons Attribution License.
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2026-04-08
2026-04-11

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Comparative genomic and resistance characterization of ST2 and ST164 carbapenem-resistant Acinetobacter baumannii from hospital environments and clinical specimens
M Gen 12, 001679 (2026); https://doi.org/10.1099/mgen.0.001679
/content/journal/mgen/10.1099/mgen.0.001679
/content/journal/mgen/10.1099/mgen.0.001679
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