Carbapenemase-producing Acinetobacter baumannii from Spanish hospitals, 2016-2020: Interregional spread of ST2PAS isolates co-harbouring blaOXA-23, blaOXA-66 and armA genes.
Aug 2026· International Journal of Antimicrobial Agents· pp.
107967
· 0 citations· 41 references
Medicine
TL;DR
In Spain, CRAB dissemination is driven by interregional spread of isolates belonging to the ST218Oxf/ST2Pas clones, characterized by the blaOXA-23/blaOXA-66 genotype, the presence of armA, the KL7/OCL18 capsular profile and the presence of pS32-1 plasmid.
Abstract
INTRODUCTION AND
Aims
Carbapenem-resistant Acinetobacter baumannii (CRAB) poses a serious global threat, prioritized by the WHO for new antibiotic development. The ECDC proposed the integration of genomic sequencing into surveillance. This study characterizes phenotypic and genotypic features of nationwide-collected CRAB isolates from Spanish hospitals (2016-2020).
Materials And Methods
A total of 822 CRAB isolates sent to the Spanish reference laboratory were analyzed, and 108 representative isolates were selected from 48 hospitals in 25 Spanish provinces. Antibiotic susceptibility was determined according to EUCAST guidelines, and WGS was performed by Illumina. Resistome, virulome, phylogeny (cgMLST; 2390 genes), insertion sequences and plasmids were analyzed.
Results
Of the 108 representative isolates, 68.5% produced OXA-23, 10.2% OXA-24, 7.4% OXA-58, 1.9% NDM-1 and 2.7% others. 3.7% co-produced two acquired carbapenemases, and six that did not have them showed the ISAba1 upstream of the blaOXA-51 like. The predominant STs were ST2pas (82.4%) and ST218Oxf (61.1%). blaOXA-66 chromosomal carbapenemase allele was present in 75% of the 108 isolates, armA 16s rRNA methyltransferase gene in 61.1% and the kL-7/OCL-18 was present in 59.3% of the isolates. The most active antibiotic was colistin. 65.4% of invasive cases were caused by isolates harboring all 38 virulence genes tested. In the 64.8% of isolates a plasmid type was detected, mainly pS32-1-like (54.6%).
Conclusions
In Spain, CRAB dissemination is driven by interregional spread of isolates belonging to the ST218Oxf/ST2Pas clones, characterized by the blaOXA-23/blaOXA-66 genotype, the presence of armA, the KL7/OCL18 capsular profile and the presence of pS32-1 plasmid.
OBJECTIVES
The numbers of infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) are increasing globally and present a significant burden on healthcare systems. This study describes the CRAB isolates received at the Swiss National Reference Centre for Emerging Antibiotic Resistance (NARA) over a 3-year period, from January 2022 to December 2025, and aimed to characterize the prevalence and mechanisms of FDC resistance.
METHODS
Two-hundred and thirty-four non-duplicate CRAB isolates were submitted to NARA over the study period from hospitals and laboratories across Switzerland. Susceptibility testing was performed by disk diffusion and broth microdilution, according to EUCAST methodology. Whole-genome sequencing was performed on 11 isolates. ADC alleles were cloned into vector pVRL1 and transformed into Escherichia coli Top10.
RESULTS
All isolates exhibited resistance to the carbapenems, and most were resistant to cephalosporins. Most isolates harboured an acquired class D carbapenemase, most frequently OXA-23 (181/234; 77.4%). One quarter of isolates were resistant to cefiderocol (FDC), exhibiting MICs ranging from 4->32 mg/L. Whole genome sequencing analyses, performed on 11 FDC-resistant isolates, identified that FDC resistance was due a combination of mechanisms including NDM and PER-production, mutations within the iron transporters, piuA and pirA, and the overexpression of ADC variants.
CONCLUSIONS
This study showed that OXA-23 was the dominant mechanism of carbapenem-resistance in CRAB in Switzerland. Almost one quarter of CRAB isolates were resistant to "last resort" antimicrobial, FDC. The mechanisms of FDC resistance identified in this study emphasise that resistance to this antimicrobial is often complex and multifactorial, requiring high-resolution methods, including WGS, to identify.
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