Transmission of Carbapenemase Genes in Enterobacter cloacae:
2026-04-12
Transmission of Carbapenemase Genes in Enterobacter cloacae: Insights from Guangdong Hospitals (2022–2024)
Study Background and Research Question
Carbapenem-resistant Enterobacteriaceae (CRE) present a growing global health challenge, with Enterobacter cloacae (CREC) ranking as a major contributor to nosocomial infections. The COVID-19 pandemic has exacerbated antibiotic resistance trends due to increased antimicrobial use and healthcare disruptions. However, the specific dynamics and genetic architecture of carbapenemase-encoding genes (CEGs) in CREC during this period have remained underexplored. The referenced multicenter study [source_type: paper][source_link: https://doi.org/10.1186/s12866-025-04300-0] addresses this gap by systematically analyzing 54 CREC isolates collected from eight tertiary hospitals in Guangdong, China, between December 2022 and June 2024. The primary research question centers on the prevalence, genomic localization, and transmission mechanisms of CEGs, with a particular focus on the blaNDM−1, blaIMP, and blaKPC−2 genes.Key Innovation from the Reference Study
The study's foremost innovation lies in its integrative approach to characterizing both the genetic compartmentalization (chromosomal vs. plasmid) and the horizontal transfer efficiency of CEGs in a clinically relevant cohort. By employing a combination of plasmid elimination, PCR-based genotyping, and conjugation assays, the authors provide a high-resolution view of resistance gene mobility and its epidemiological correlates [source_type: paper][source_link: https://doi.org/10.1186/s12866-025-04300-0]. The investigation uniquely quantifies the success rates of resistance gene transfer events, a parameter critical for understanding the pace at which multidrug resistance may spread within and between healthcare settings.Methods and Experimental Design Insights
The study used a robust workflow integrating molecular and phenotypic assays:- Sample Collection: 54 CREC isolates were obtained from a spectrum of clinical departments (e.g., respiratory medicine) and specimen types (notably sputum) across eight teaching hospitals.
- Genetic Analysis: Variable temperature sodium dodecyl sulfate (SDS) plasmid elimination and PCR amplification were deployed to detect and localize CEGs (blaNDM−1, blaIMP, blaKPC−2) on chromosomes and/or plasmids.
- Resistance Profiling: Antimicrobial susceptibility was determined using the broth microdilution method, comparing CEG-positive and CEG-negative isolates across multiple antibiotics, including imipenem, cefepime, gentamicin, ceftazidime/avibactam, ciprofloxacin, and levofloxacin.
- Gene Transfer Studies: Plasmid conjugation experiments assessed the efficiency of horizontal gene transfer for CEGs among isolates.
- Genotyping and Epidemiology: ERIC-PCR and NTSYS software facilitated strain typing, while epidemiological data were stratified by gender, age, clinical department, and specimen category.
Protocol Parameters
- assay | broth microdilution | antibiotic resistance profiling | to quantitatively assess minimum inhibitory concentrations against key antibiotics (imipenem, cefepime, gentamicin, ceftazidime/avibactam, ciprofloxacin, levofloxacin) | paper [https://doi.org/10.1186/s12866-025-04300-0]
- assay | variable temperature SDS plasmid elimination | CEG localization | to distinguish chromosomal versus plasmid-borne resistance genes | paper [https://doi.org/10.1186/s12866-025-04300-0]
- assay | PCR amplification | gene identification | confirm presence of blaNDM−1, blaIMP, blaKPC−2 in isolates | paper [https://doi.org/10.1186/s12866-025-04300-0]
- assay | conjugation experiment | horizontal transfer efficiency measurement | quantify transmissibility of CEGs between strains | paper [https://doi.org/10.1186/s12866-025-04300-0]
Core Findings and Why They Matter
Prevalence and Localization of Resistance Genes:- 85.19% (46/54) of CREC isolates were CEG-positive, with blaNDM−1 being the predominant gene [source_type: paper][source_link: https://doi.org/10.1186/s12866-025-04300-0].
- blaNDM−1 was present on both chromosomes and plasmids in 33.33% (18/54) of isolates, and exclusively on plasmids in 46.30% (25/54) [source_type: paper][source_link: https://doi.org/10.1186/s12866-025-04300-0].
- Other detected genes included blaIMP (3.70%) and co-occurrence of blaNDM−1 and blaKPC−2 (1.85%).
- CEG-positive isolates displayed significantly higher resistance rates to all tested antibiotics, including levofloxacin, compared to CEG-negative isolates (P<0.05) [source_type: paper][source_link: https://doi.org/10.1186/s12866-025-04300-0].
- Plasmid-mediated CEGs exhibited a 95.65% (44/46) successful transfer rate in conjugation assays, highlighting robust potential for horizontal dissemination [source_type: paper][source_link: https://doi.org/10.1186/s12866-025-04300-0].
- blaNDM−1 transfer success was 95.45% (42/44); blaIMP transfer was 100% (2/2); blaKPC−2 did not transfer in this cohort.
- Six MGEs were identified, with ISEcp1 being most prevalent (87.04%, 47/54). The majority of isolates harbored multiple MGEs, facilitating gene dispersal [source_type: paper][source_link: https://doi.org/10.1186/s12866-025-04300-0].
- ERIC-PCR typing revealed 17 genotypes, with types E and G most frequent (each 20.37%). The same genotype was found in isolates from different hospitals, indicating inter-hospital dissemination.
- Higher detection rates of CEGs in male patients (64.81%), elderly individuals (72.22%), respiratory medicine wards (20.37%), and sputum samples (33.33%) [source_type: paper][source_link: https://doi.org/10.1186/s12866-025-04300-0].