# P-1567. Prevalence of the acrB Gene in Class 1 Integrons Among Carbapenem-Resistant Enterobacterales in Southern Taiwan

## TL;DR

This study found that the acrB gene is common in class 1 integrons among carbapenem-resistant bacteria in Southern Taiwan, contributing to multidrug resistance.

## Contribution

The study reports the prevalence of acrB gene within class 1 integrons in carbapenem-resistant Enterobacterales and experimentally confirms its role in multidrug resistance.

## Key findings

- The acrB gene was detected in 47.5% of class 1 integron-positive CRE isolates.
- acrB knockout strains showed reduced MICs for several antibiotics compared to parental strains.
- No changes in carbapenem susceptibility were observed in acrB knockout strains.

## Abstract

Acriflavine resistance protein B (acrB) serves as the drug specificity and energy transduction component of the AcrAB-TolC multidrug efflux system. This study aimed to investigate the prevalence of the acrB gene within class 1 integrons among carbapenem-resistant Enterobacterales (CRE) clinical isolates in Southern Taiwan.Table 1.Class 1 Integron Cassettes Carrying acrB genes detected by PCR in clinical isolates of CP-producing CRE in Southern Taiwan (N=80)Table 2.Comparison of Minimum Inhibitory Concentrations (MICs, µg/mL) Between acrB Gene Knockout Strains and Parental Strains in Antimicrobial Susceptibility Testing

Class 1 Integron Cassettes Carrying acrB genes detected by PCR in clinical isolates of CP-producing CRE in Southern Taiwan (N=80)

Comparison of Minimum Inhibitory Concentrations (MICs, µg/mL) Between acrB Gene Knockout Strains and Parental Strains in Antimicrobial Susceptibility Testing

A total of 101 CRE isolates were collected from 2020 to 2023. Genomic DNA was extracted, followed by PCR detection of class 1 integron genes. These integron gene templates were subsequently used for PCR amplification and sequencing of the acrB and carbapenemase genes. acrB knockout strains were constructed, and the minimum inhibitory concentrations (MICs) of selected antibiotics were determined using the Vitek 2 system.

Class 1 integrons were detected in 79.2% (80/101) of CRE isolates. Among these 47.5% (38/80) harbored the acrB gene. The highest prevalence of integron-associated acrB was found in Citrobacter freundii (83.3%, 5/6), followed by Enterobacter spp. (68.8%, 11/16), Klebsiella pneumoniae (47.7%, 21/44), and Escherichia coli (7.1%, 1/14). MICs for ciprofloxacin, levofloxacin, tigecycline, minocycline, moxifloxacin, and tetracycline were reduced by 2- to 16-fold in acrB knockout strains compared to their corresponding parental strains.However, no changes were observed in carbapenem susceptibility.

This study reveals a high prevalence of the acrB gene within class 1 integrons among CRE isolates in Southern Taiwan. The observed reduction in MICs in acrB knockout mutants supports the role of AcrB in multidrug resistance and emphasizes the need for further research into its functional role and evolutionary significance.

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