Emergence of extensively drug-resistant hypervirulent Acinetobacter baumannii isolated from patients with bacteremia: bacterial phenotype and virulence analysis

Pek Kee Chen; Chia-Ying Liu; Han-Yueh Kuo; Yi-Tzu Lee; Yu-Han Liu; Yen-Zhen Zhang; Cheng-Yen Kao

doi:10.1016/j.ijantimicag.2024.107358

Emergence of extensively drug-resistant hypervirulent Acinetobacter baumannii isolated from patients with bacteremia: bacterial phenotype and virulence analysis

Int J Antimicrob Agents. 2024 Oct 14:107358. doi: 10.1016/j.ijantimicag.2024.107358. Online ahead of print.

Authors

Pek Kee Chen¹, Chia-Ying Liu², Han-Yueh Kuo³, Yi-Tzu Lee⁴, Yu-Han Liu⁵, Yen-Zhen Zhang¹, Cheng-Yen Kao⁶

Affiliations

¹ Institute of Microbiology and Immunology, College of Life Sciences, National Yang Ming Chiao Tung University, Taipei, Taiwan.
² Department of Internal Medicine, Far Eastern Memorial Hospital, New Taipei City, Taiwan.
³ National Taiwan University Hospital Hsin-Chu Branch, Hsin-Chu, Taiwan; National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan.
⁴ Department of Emergency Medicine, Taipei Veteran General Hospital, Taipei, Taiwan; School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan.
⁵ Department of Emergency Medicine, Taipei Veteran General Hospital, Taipei, Taiwan.
⁶ Institute of Microbiology and Immunology, College of Life Sciences, National Yang Ming Chiao Tung University, Taipei, Taiwan; Health Innovation Center, National Yang Ming Chiao Tung University, Taipei, Taiwan; Microbiota Research Center, National Yang Ming Chiao Tung University, Taipei, Taiwan. Electronic address: kaocy@nycu.edu.tw.

PMID: 39414173
DOI: 10.1016/j.ijantimicag.2024.107358

Abstract

Objectives: Individuals infected with extensively drug-resistant (XDR) Acinetobacter baumannii are difficult to cure and have a high mortality rate. In this study, we compared the genomic and phenotypic differences between XDR and non-multidrug-resistant (MDR) A. baumannii and further characterized hypervirulent XDR A. baumannii.

Methods: A total of 1,403 Acinetobacter isolates were collected from patients with bacteremia between 1997 and 2015. Antimicrobial susceptibility test was performed to categorize isolates into non-MDR, MDR, and XDR groups. The presence of selected virulence-associated genes was determined by PCR. Bacterial phenotypes, including iron acquisition, biofilm formation, capsule production, and virulence to larvae and mice, were determined.

Results: Multilocus sequence types revealed the high prevalence of ST2 (81.6%) and ST129 (18.4%) among 49 XDR isolates and sequence types of 18 non-MDR isolates were more diverse. Virulence-associated phenotypic assays showed that XDR isolates had higher iron acquisition ability and capsule production and higher virulence to Galleria mellonella larvae. However, their biofilm formation ability was lower compared to that of non-MDR isolates. XDR isolates contained more virulence genes, tonB, hemO, abaI, and ptk, while non-MDR isolates contained more pld and ompA. Twenty-one XDR isolates caused <20% larvae survival rate after 7 days post-infection were defined as hypervirulent XDR isolates. Among them, isolates 1677 (ST129) and 929-1 (ST2) also caused the death of all infected mice within two days.

Conclusion: Some subpopulations of highly drug-resistant ST2 also exhibit high virulence. Therefore, it is of utmost importance to continue monitoring the spread of hypervirulent XDR A. baumannii isolates.

Keywords: Acinetobacter baumannii; capsule production; extensively drug-resistant; hypervirulent; iron acquisition.