# Epidemiological and genomic characteristics of Ralstonia mannitolilytica isolated from bloodstream in Liaocheng City, Shandong Province, China

## TL;DR

This study examines 11 Ralstonia mannitolilytica bloodstream infections in a Chinese hospital, revealing two transmission clusters and the bacterium's resistance to multiple antibiotics.

## Contribution

The study provides novel comparative genomic insights into R. mannitolilytica's resistance mechanisms and evolutionary adaptability.

## Key findings

- All isolates showed multidrug resistance, including resistance to carbapenems like imipenem and meropenem.
- Genomic analysis identified two distinct clades, indicating separate nosocomial transmission events.
- Intrinsic resistance genes (blaOXA-22-like, blaOXA-60-like) and efflux pumps (qacJ, adeF) were linked to antimicrobial resistance.

## Abstract

Ralstonia mannitolilytica, primarily recognized as an environmental bacterium, has emerged as an opportunistic pathogen associated with nosocomial infections. R. mannitolilytica is well-adapted to oligotrophic and humid environments, harbors intrinsic resistance to both disinfection measures and antimicrobial therapies and possesses the ability to bypass 0.2 µm filters, thereby facilitating its persistence in clinical and environmental reservoirs. In this study, 11 R. mannitolilytica isolates were isolated from bloodstream infection cases at a tertiary hospital in Liaocheng City, China, between November 2019 and November 2021. Clinical data, antimicrobial susceptibility profiles, and whole-genome sequencing were analyzed to investigate the resistance mechanisms, genomic characteristics, and clonal dissemination patterns. All isolates exhibited multidrug resistance, exhibiting resistance to ceftazidime, amikacin, gentamicin, imipenem, meropenem, polymyxin B, ceftazidime/avibactam, and chloramphenicol, while retaining susceptibility to minocycline, cefotaxime, cefepime, trimethoprim/sulfamethoxazole, tigecycline, and tetracycline. Core genome multilocus sequence typing and average nucleotide identity analyzes revealed two distinct clades, suggesting independent nosocomial transmission events. Genomic characterization uncovered the presence of intrinsic blaOXA-22-like and blaOXA-60-like carbapenemase genes, along with efflux pump genes (qacJ, adeF), contributing to resistance. Although the infection sources remain unresolved, this study demonstrates the utility of genomic surveillance in tracking hospital-acquired R. mannitolilytica outbreaks and advocates for stringent infection control measures to mitigate the spread of this opportunistic pathogen. This report provides novel comparative genomic insights into R. mannitolilytica, enhancing understanding of its resistance mechanisms and evolutionary adaptability.

Ralstonia mannitolilytica, an environmental bacterium increasingly linked to hospital-acquired infections, poses significant treatment challenges due to its resistance to common antibiotics. This study investigates 11 bloodstream infection cases caused by R. mannitolilytica in a Chinese hospital, revealing two distinct transmission clusters through genomic analysis. The findings highlight the bacterium’s ability to persist in clinical settings and its resistance to critical antibiotics like carbapenems, likely driven by intrinsic genes and efflux pumps. By combining patient data and genomic surveillance, this work underscores the urgent need for enhanced infection control measures to curb outbreaks. It also provides novel comparative genomic insights into R. mannitolilytica, advancing our understanding of its evolution and resistance mechanisms, which is vital for guiding future clinical management and public health strategies.