Genomic insights of the co-existence of blaOXA-23, blaOXA-91, blaNDM-1 harboring carbapenem-resistant Acinetobacter Baumannii isolates from the intensive care units environment in Shanghai.

OBJECTIVES

This study assessed the transmission, prevalence and genomic characteristics of carbapenem-resistant Acinetobacter Baumannii (CARB) isolated from object surfaces and healthcare workers' hands in seven hospitals of Shanghai in 2019 (pre-COVID pandemic) and 2023 (post-COVID pandemic).

METHODS

CRAB isolates were tested for antimicrobial susceptibility using the broth microdilution method and whole-genome sequencing. Antimicrobial resistance genes, Multilocus Sequence Typing (MLST), polysaccharide capsule and plasmid migration were evaluated based on tools such as VFDB database, PubMLST, Kaptive, MOB-suite, etc.

RESULTS

Of 3,156 samples collected, 130 strains of CRAB were isolated. The prevalence of CRAB in the ICU setting was significantly lower in 2023 (2.44%) than in 2019 (5.60%). Objects that come into direct contact with patients served as a primary source (43.85%). CRAB isolates exhibited higher resistance to β-lactamase antibiotics but lower to minocycline (2.31%), tigecycline (3.08%) and polymyxin B (2.31%). Five ST_Pasteur and eleven ST_Oxford were identified, predominantly ST2_Pasteur (93.6%) and ST208_Oxford (40%). Two novel sequence types (STs) named ST3329 and ST3331 were found in the surface of objects such as door handles. Notably, two CARB isolates (designated 2023-AB023 and 2023-AB033) co-harboring the blaOXA-23, blaOXA-91, blaNDM-1 were found to be high genomic similarity to DETAB-R21 previously isolated from an ICU patient's oral swab with high environmental adaptability, reported in August 2022 in Zhejiang Province of China.

CONCLUSIONS

The resistance rate of CRAB was slightly lower in 2023 compared to 2019. However, the emergence of pan-drug-resistant CRAB, along with the coexistence of carbapenemase-producing strains (OXA-23, OXA-51-like, and NDM-1) in 2023, underscore the dynamic progression of antimicrobial resistance (AMR) in this pathogen. These findings suggest a potential epidemiological shift characterized by clonal diversification alongside persistent carbapenemase-driven resistance mechanisms.