# Distribution characteristics of integrons and correlation analysis of antibiotic resistance in Aeromonas hydrophila

## TL;DR

This study explores how integrons contribute to antibiotic resistance in Aeromonas hydrophila and identifies specific resistance genes linked to clinical isolates.

## Contribution

The study identifies the role of class 1 integrons and specific resistance gene cassettes in mediating multidrug resistance in Aeromonas hydrophila clinical isolates.

## Key findings

- Class 1 integrons were detected in 20% of Aeromonas hydrophila isolates, with catB8 and aadA1 as common resistance gene cassettes.
- Integron-positive strains showed higher resistance to multiple antibiotics compared to integron-negative strains.
- ERIC-PCR revealed high clonal similarity among integron-positive strains, suggesting potential hospital-based dissemination.

## Abstract

This study aims to investigate the distribution of integrons in clinically isolated Aeromonas hydrophila from our hospital, as well as the correlation between antibiotic resistance, resistance genes and integrons carried by Aeromonas hydrophila. Through molecular characterization of integrons and associated resistance gene cassettes, we seek to gain an in-depth understanding of the role of integrons in mediating multidrug resistance in Aeromonas hydrophila, thereby providing a basis for more effective infection control strategies.

We collected 80 strains of clinically isolated Aeromonas hydrophila from January 2021 to December 2024 and performed antimicrobial susceptibility testing on them. Polymerase chain reaction (PCR) was used to screen these strains for class 1, 2, and 3 integrons, resistance genes, and virulence factors. Subsequently, the variable regions of integron-positive strains were amplified and sequenced. An analysis was conducted to assess the correlation among bacterial drug resistance, resistance genes, virulence genes, and integrons. Additionally, enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) was employed to assess the clonal relatedness of integron-positive strains.

Among the 80 clinical isolates, 16 (20.0%) were positive for class 1 integrons, while no class 2 or 3 integrons were detected. Amplification of the variable regions of class 1 integrons identified four resistance gene cassettes, predominantly catB8 and aadA1. The integron-positive strains exhibited significantly higher resistance rates to ceftazidime, gentamicin, imipenem, trimethoprim-sulfamethoxazole, and amikacin compared to integron-negative strains (P < 0.05). Additionally,The detection rate of β-lactamase gene MOX in drug-resistant genes was the highest, accounting for 62.5%, and the detection rate of virulence gene ast was the highest, accounting for 65.0%. ERIC-PCR typing classified the 16 integron-positive strains into seven genotypes, with type C being the most predominant. The catB8-aadA1 gene cassette was mostly found in type C strains, which were predominantly isolated from the Hepatobiliary and Pancreatic Surgery Department.

Our study reveals that class 1 integrons are the predominant type carried by Aeromonas hydrophila clinical isolates in our hospital. The aminoglycoside resistance gene aadA1 and the chloramphenicol resistance gene catB8, identified within the variable regions of these integrons, are directly associated with corresponding antibiotic resistance phenotypes. Notably, integron-positive strains displayed high clonal similarity, with the dominant ERIC genotype C indicating potential clonal dissemination within the hospital setting. These findings suggest that integrons, along with their carried resistance gene cassettes, could serve as useful molecular markers for epidemiological surveillance of multidrug-resistant Aeromonas hydrophila. Implementing routine screening for integrons and associated resistance genes in high-risk wards, such as hepatobiliary surgery, could enhance targeted infection control measures and help prevent the spread of resistant clones, including those of emerging pathogens like A. hydrophila.