Transmission and Genetics of Carbapenemase Resistance in CRE

2026-07-10

Transmission and Genetics of Carbapenemase Resistance in CREC in China

Study Background and Research Question

Carbapenem-resistant Enterobacter cloacae (CREC) represents an escalating threat to healthcare systems worldwide, contributing to rising rates of untreatable Gram-negative infections. In China, CREC ranks as the third most frequently detected carbapenem-resistant Enterobacteriaceae (CRE), following Klebsiella pneumoniae and Escherichia coli. The COVID-19 pandemic has further complicated this landscape, with increased antibiotic usage and healthcare disruptions accelerating the emergence and spread of resistance. Despite this urgency, the molecular epidemiology and transmission dynamics of carbapenemase-encoding genes (CEGs) in clinical CREC strains, particularly during the pandemic, remain insufficiently understood. The reference paper by Chen et al. (2025) directly addresses this gap by systematically analyzing CREC isolates from eight teaching hospitals in Guangdong province between 2022 and 2024 (reference study).

Key Innovation from the Reference Study

The core innovation of this work lies in its integrated molecular and epidemiological analysis of CEGs in CREC during a period of heightened resistance pressures. By combining plasmid elimination, PCR screening, plasmid conjugation, and genotyping, the study not only quantifies CEG prevalence but also elucidates their genetic context (chromosomal versus plasmid localization), mobility, and patterns of dissemination within and across clinical settings. The research uniquely demonstrates the predominance of plasmid-borne blaNDM-1 and the extensive horizontal transferability of these resistance determinants, providing critical insights for modeling the spread of carbapenem resistance.

Methods and Experimental Design Insights

The study analyzed 54 non-duplicate CREC isolates collected from diverse clinical departments over an 18-month period. Isolates underwent variable temperature SDS plasmid elimination to distinguish chromosomal from plasmid-borne resistance determinants, followed by PCR amplification for blaNDM-1, blaIMP, and blaKPC-2 detection. Broth microdilution was used to determine minimal inhibitory concentrations (MICs) for a panel of antibiotics, assessing multidrug resistance profiles. Plasmid conjugation assays evaluated the transferability of detected CEGs into recipient strains. Additionally, the presence of mobile genetic elements (MGEs) was systematically characterized, and ERIC-PCR fingerprinting with NTSYS clustering established the genotypic relationships among isolates.

Protocol Parameters

Isolate collection: 54 CREC strains from eight tertiary hospitals, December 2022–June 2024.
Plasmid elimination: Variable temperature SDS method to distinguish plasmid versus chromosomal gene localization.
PCR screening: Detection of blaNDM-1, blaIMP, and blaKPC-2 genes; further analysis for mobile genetic elements (ISEcp1, others).
Antibiotic susceptibility: Broth microdilution for imipenem, cefepime, gentamicin, ceftazidime/avibactam, ciprofloxacin, and levofloxacin.
Plasmid conjugation: Transfer assays to quantify horizontal gene transfer frequency.
Genotyping: ERIC-PCR and NTSYS software for cluster analysis of genetic relationships.

Core Findings and Why They Matter

The study reports an 85.2% detection rate of carbapenemase-encoding genes among CREC isolates, with blaNDM-1 accounting for the majority—present on both chromosomes and plasmids in 33.3% and exclusively on plasmids in 46.3% of isolates. Minority populations carried blaIMP (3.7%) or both blaNDM-1 and blaKPC-2 (1.9%). Significantly, CEG-positive isolates exhibited elevated resistance to multiple antibiotics, including imipenem, cefepime, gentamicin, and fluoroquinolones, compared to CEG-negative isolates, highlighting a strong association between CEG carriage and multidrug resistance (reference study). Horizontal gene transfer potential was robust: 95.7% of CEG-positive isolates successfully transferred their resistance genes in conjugation assays, with the blaNDM-1 gene demonstrating a 95.5% transfer success rate. Six different mobile genetic elements were identified, dominated by ISEcp1 (87.0%), and a notable proportion of isolates (40.7%) harbored four types of MGEs concurrently, suggesting a highly dynamic and mobile resistance gene pool. Genotypic analysis via ERIC-PCR clustered the isolates into 17 genotypes, with two major clusters (type E and G) each representing over 20% of cases and distributed across multiple hospitals and departments. Epidemiologically, CEG-positive CREC was more frequently detected in male and elderly patients, within respiratory medicine, and in sputum samples. These findings underscore the centrality of plasmid-mediated blaNDM-1 and MGEs in the rapid, horizontal dissemination of carbapenem resistance. The clear correlation with multidrug resistance and genotype clustering across hospitals emphasizes the risk of inter- and intra-hospital outbreaks.

Comparison with Existing Internal Articles

These results are congruent with prior syntheses on the mechanisms and clinical impact of carbapenem resistance in Gram-negative bacteria. The internal article Transmission Dynamics of Carbapenemase Genes in CREC in China similarly documents the high prevalence and transferability of β-lactamase genes, reinforcing the role of horizontal plasmid transfer in resistance proliferation. In addition, Meropenem in Translational Antibacterial Research provides mechanistic context on how β-lactam antibiotic carbapenems interact with penicillin-binding proteins (PBPs) in both Gram-negative and Gram-positive bacteria, highlighting the importance of reliable experimental models for evaluating resistance emergence and antibacterial efficacy. Practical workflow articles such as Meropenem: β-Lactam Carbapenem Workflows for Resistance Models offer stepwise guidance for modeling Gram-negative bacterial infection and resistance, indicating that the experimental approaches used in the reference study are consistent with contemporary translational research standards.

Limitations and Transferability

While the study achieves broad sampling across multiple hospital centers and departments, the sample size (54 isolates) limits the granularity of epidemiological conclusions, particularly concerning rare CEG subtypes or less common MGEs. The focus on Guangdong province means that geographic variability and unique local transmission patterns may not be generalizable nationwide or internationally. Furthermore, the absence of patient-level clinical outcome data constrains correlation between genotype, resistance phenotype, and infection severity. Nevertheless, the rigorous application of molecular, phenotypic, and epidemiological techniques makes these findings highly transferable to other settings seeking to characterize and control the spread of carbapenem-resistant Enterobacteriaceae. The high horizontal transfer rates observed for plasmid-borne resistance genes strongly suggest that infection control efforts should prioritize both antimicrobial stewardship and containment of mobile genetic elements.

Research Support Resources

For researchers aiming to replicate or extend these workflows in laboratory or translational models, standardized reagents are essential. Meropenem (SKU A5124) from APExBIO offers an ultra-broad-spectrum β-lactam antibiotic carbapenem suitable for modeling antibacterial activity and resistance mechanisms in both Gram-negative and Gram-positive bacteria. Its defined solubility and stability parameters support reproducible in vitro and in vivo experimentation, including septicemia treatment research and Gram-negative bacterial infection models. For technical details, refer to the product information and relevant workflow articles. As always, Meropenem is supplied for research use only and is not intended for clinical or diagnostic applications.