Transmission Dynamics of Carbapenemase Genes in CREC in Guan

2026-06-03

Transmission Dynamics of Carbapenemase-Encoding Genes in Carbapenem-Resistant Enterobacter cloacae: Insights from Eight Hospitals in Guangdong (2022–2024)

Study Background and Research Question

Carbapenem-resistant Enterobacteriaceae (CRE) represent a severe and growing public health threat, with carbapenem-resistant Enterobacter cloacae (CREC) ranking as one of the most prevalent CRE species, particularly in China. The global COVID-19 pandemic has intensified concerns about antimicrobial resistance by disrupting healthcare systems and increasing antibiotic use, thus potentially accelerating the emergence and spread of multidrug-resistant organisms. Despite this, comprehensive molecular epidemiology studies of carbapenemase-encoding genes (CEGs) in CREC, especially concerning their localization and transmission dynamics during the pandemic, have been limited. The study by Chen et al. (BMC Microbiology, 2025) addresses this gap by systematically analyzing CREC isolates collected from multiple teaching hospitals in Guangdong Province between 2022 and 2024.

Key Innovation from the Reference Study

The central innovation of the reference study lies in its in-depth analysis of the genetic architecture, prevalence, and transmissibility of CEGs in CREC during a period marked by pandemic-driven changes in antibiotic usage and hospital practices. By combining molecular typing, plasmid profiling, and conjugation assays, the authors map both the vertical and horizontal spread of resistance genes, with a particular focus on bla_NDM-1, bla_IMP, and bla_KPC-2. The study provides new evidence on how these genes are distributed across both plasmids and chromosomes, and quantifies their transfer rates between bacterial populations in clinical environments.

Methods and Experimental Design Insights

The study analyzed 54 CREC isolates obtained from eight tertiary teaching hospitals over an 18-month period. Core methodological elements included:

Plasmid Elimination and PCR Detection: Variable temperature sodium dodecyl sulfate (SDS) plasmid elimination allowed for the differentiation of chromosomal and plasmid localization of CEGs, followed by PCR for gene identification.
Resistance Phenotyping: Broth microdilution assays determined susceptibility profiles for multiple antibiotics, including carbapenems, cephalosporins, aminoglycosides, and fluoroquinolones, highlighting the multidrug resistance landscape.
Plasmid Conjugation Assays: Mating experiments quantified the transferability of CEGs, assessing the efficiency of horizontal gene transfer.
Genotyping and Epidemiology: ERIC-PCR and NTSYS software were used to cluster genetic types, while epidemiological data correlated gene detection rates with patient demographics, clinical departments, and specimen types.
Mobile Genetic Element Analysis: PCR identified six types of mobile elements associated with CEGs, with a focus on their prevalence and combinatorial patterns.

Protocol Parameters

Sample collection window: December 2022 to June 2024, ensuring coverage of pandemic and post-pandemic shifts in clinical practice.
Plasmid elimination: Variable temperature SDS treatment for distinguishing chromosomal versus plasmid gene localization.
Conjugation assay setup: Standard filter mating methods; successful transfer confirmed by PCR in 95.65% of CEG-positive isolates.
Resistance determination: Broth microdilution for imipenem, cefepime, gentamicin, ceftazidime/avibactam, ciprofloxacin, and levofloxacin, stratified by CEG status.
Genotype clustering: ERIC-PCR typing with NTSYS similarity analysis; 17 genotypes identified among 54 isolates.

Core Findings and Why They Matter

The study establishes several pivotal findings:

High CEG Prevalence: 85.19% of CREC isolates harbored CEGs, with bla_NDM-1 being predominant. Notably, 33.33% carried bla_NDM-1 on both chromosomes and plasmids, while 46.30% carried it exclusively on plasmids.
Diverse Genetic Carriage: bla_IMP and bla_KPC-2 were also detected, albeit less frequently, often co-localized with bla_NDM-1 in rare cases.
Multidrug Resistance: CEG-positive isolates exhibited significantly higher resistance rates to key antibiotics, especially imipenem, cefepime, and ceftazidime/avibactam, compared to CEG-negative strains.
Efficient Horizontal Transfer: Conjugation assays demonstrated a 95.65% success rate in transferring CEGs, underscoring the robust potential for rapid spread in clinical environments.
Mobile Elements and Genotype Diversity: The insertion sequence ISEcp1 was the most prevalent (87.04%), and strains often carried multiple mobile genetic elements. Seventeen distinct genotypes were identified, with some showing 100% similarity, indicating clonal expansion in certain hospital departments.
Epidemiological Trends: CEGs were most frequently detected in male and elderly patients, with respiratory medicine and sputum samples showing the highest rates of isolation.

These results have direct implications for infection control and the design of bacterial infection models and antimicrobial resistance research workflows, particularly in settings where third-generation cephalosporin antibiotics are benchmarks for comparative efficacy and resistance mechanism studies.

Comparison with Existing Internal Articles

The findings from Chen et al. align with and extend insights from several recent reviews and technical articles focusing on the strategic use of Cefotaxime in resistance research:

"Cefotaxime: Beta-Lactamase-Resistant Cephalosporin for Gram-Positive and Gram-Negative Bacteria" discusses the role of Cefotaxime as a model compound for studying beta-lactamase-mediated resistance, paralleling the reference study's focus on mobile gene elements and transmission dynamics.
"Cefotaxime in Antimicrobial Resistance: Dynamic Assay Strategies" explores advanced assay design using third-generation cephalosporin antibiotics, supporting the reference study's emphasis on multidrug resistance profiling and workflow reproducibility.
"Cefotaxime: Third-Generation Cephalosporin in Resistance Research" underscores the utility of lactamase-resistant cephalosporins in modeling horizontal gene transfer, resonating with the high conjugation success rates observed by Chen et al.

Collectively, these resources contextualize the reference study within a broader framework of beta-lactam antibiotic mechanism research and laboratory modeling of Gram-positive and Gram-negative bacterial infections.

Limitations and Transferability

While the study offers a robust molecular epidemiology snapshot, its findings are geographically constrained to Guangdong Province and may not fully capture transmission dynamics in other regions or healthcare systems. The 18-month sampling window, coinciding with the COVID-19 pandemic, may have introduced unique selection pressures, potentially limiting generalizability. The focus on teaching hospitals also suggests findings may not extend to community settings with differing antimicrobial stewardship practices. Furthermore, while plasmid and chromosomal localization of CEGs was elucidated, the functional impact on treatment outcomes was not directly assessed, nor were in vivo infection models deployed.

Research Support Resources

For researchers aiming to model multidrug resistance and study the transmission of carbapenemase genes in Enterobacteriaceae, third-generation cephalosporin antibiotics such as Cefotaxime (SKU BA1012) from APExBIO can be incorporated into susceptibility assays and resistance mechanism protocols. Cefotaxime's resistance to beta-lactamase enzymes and broad-spectrum activity against both Gram-positive and Gram-negative bacteria make it a valuable tool for replicating and extending workflows demonstrated in the reference study. It is recommended to use freshly prepared solutions and follow storage guidelines to maintain experimental reliability. For comprehensive guidance on workflow integration and assay parameters, consult the referenced internal and external literature.