Genomic Characterization and Transmission of Carbapenemase Genes in CREC: Insights from Guangdong Hospitals (2022–2024)

Study Background and Research Question

Carbapenem-resistant Enterobacteriaceae (CRE) represent a critical threat to global public health, with carbapenem-resistant Enterobacter cloacae (CREC) standing among the top three most frequently detected CRE strains in China. The COVID-19 pandemic intensified these challenges, exacerbating antibiotic use, disrupting healthcare operations, and complicating patient management—all factors known to accelerate the emergence and spread of multidrug-resistant bacteria. Despite rising CREC prevalence, detailed molecular studies of carbapenemase-encoding gene (CEG) dynamics in diverse clinical settings remain limited. To address this gap, Chen et al. (2025) systematically investigated the prevalence, genetic context, and transmission patterns of CEGs in CREC isolates from eight teaching hospitals in Guangdong Province between late 2022 and mid-2024.

Key Innovation from the Reference Study

The principal innovation of this work lies in its high-resolution assessment of CEG carriage and transfer in a regional, multi-hospital cohort during a period marked by profound clinical disruption. The study not only quantifies the prevalence of key resistance genes—most notably blaNDM-1—but also dissects their chromosomal and plasmid localization, horizontal transfer rates, and association with mobile genetic elements. Importantly, the authors correlate these molecular findings with clinical and epidemiological data, offering actionable insights into transmission dynamics and risk stratification.

Methods and Experimental Design Insights

• Sample Collection: Fifty-four non-duplicate CREC isolates were obtained from eight tertiary teaching hospitals in Guangdong, covering diverse departments and specimen types (notably, sputum samples and respiratory medicine sources).
• Genetic Characterization: The variable temperature SDS plasmid elimination method was paired with PCR to screen for a range of carbapenemase-encoding genes, including blaNDM-1, blaIMP, and blaKPC-2.
• Antimicrobial Susceptibility Testing: Broth microdilution was employed to determine resistance profiles against key antibiotics, providing statistical comparisons between CEG-positive and CEG-negative strains.
• Plasmid Conjugation Experiments: Horizontal gene transfer was assessed through conjugation assays, with PCR confirmation of gene movement between donor and recipient strains.
• Molecular Epidemiology: ERIC-PCR fingerprinting and NTSYS software allowed for genotyping and cluster analysis, revealing the distribution and relatedness of CREC strains across the sampled hospitals.
• Mobile Genetic Element Analysis: PCR-based screening identified six types of elements, with a focus on their co-occurrence and prevalence in driving gene mobility.

Core Findings and Why They Matter

The study uncovered several critical features of CEG epidemiology and transmission in CREC:

• High Prevalence of CEGs: 85.19% of isolates harbored carbapenemase-encoding genes, with blaNDM-1 being the dominant variant. Notably, 33.33% of isolates carried blaNDM-1 on both chromosomes and plasmids, while 46.30% had it exclusively on plasmids.
• Efficient Horizontal Transfer: Plasmid conjugation experiments revealed a striking 95.65% success rate for CEG transfer, with near-universal movement of blaNDM-1 and blaIMP between strains—highlighting the ease with which resistance can disseminate.
• Multidrug Resistance: CEG-positive CREC isolates exhibited significantly higher resistance rates to multiple antibiotics, including imipenem, cefepime, gentamicin, ceftazidime/avibactam, ciprofloxacin, and levofloxacin, as compared to CEG-negative counterparts (P<0.05).
• Mobile Genetic Element Diversity: Six element types were found, with ISEcp1 present in 87.04% of isolates, often in combination. The co-occurrence of up to four mobile elements in 40.74% of strains underscores the genomic plasticity underpinning resistance dissemination.
• Genotype and Epidemiological Patterns: Seventeen genotypes were identified, with types E and G being most prevalent and distributed across several departments and hospitals. High detection rates were associated with male and elderly patients, respiratory medicine, and sputum samples.

These findings articulate a scenario in which both chromosomal and plasmid-mediated resistance mechanisms are entrenched and readily transmissible, posing complex challenges for infection control and the development of new antimicrobial strategies.

Comparison with Existing Internal Articles

Several recent internal articles provide complementary perspectives on antimicrobial resistance research, particularly regarding the use of third-generation cephalosporin antibiotics like cefotaxime:

• "Cefotaxime in Genomic Surveillance: A New Era for AMR Research" explores how cefotaxime facilitates high-throughput genomic surveillance and resistance mapping. Chen et al.'s findings on the rapid plasmid transfer of carbapenemase genes reinforce the need for such surveillance platforms to monitor emerging resistance threats in real time.
• "Cefotaxime in Translational Antimicrobial Resistance Research" discusses the utility of cefotaxime in dissecting resistance mechanisms and modeling infection dynamics. The molecular epidemiology presented by Chen et al. directly informs these workflows, illustrating how diverse genetic backgrounds and mobile elements should be considered when designing robust bacterial infection models.
• "Cefotaxime: Third-Generation Cephalosporin in AMR Models" emphasizes the importance of beta-lactamase-resistant cephalosporins for benchmarking resistance studies. The high rate of multidrug resistance in CEG-positive CREC further validates the continued need for such agents in both experimental and surveillance contexts.

Together, these articles highlight the translational bridge from molecular epidemiology, as exemplified by Chen et al., to practical antimicrobial resistance research using established antibiotics and advanced genomic tools.

Limitations and Transferability

While the Chen et al. study offers a robust snapshot of CEG prevalence and transfer in Guangdong, several limitations merit consideration:

• The sample is geographically confined to southern China and may not capture the full spectrum of genetic diversity seen in other regions or healthcare settings.
• Longitudinal trends beyond the 2022–2024 period remain unexplored, limiting insight into resistance evolution over time.
• Although the molecular methods are rigorous, additional whole-genome sequencing could further refine the understanding of resistance gene context and mobility.

Nonetheless, the methodological framework and key conclusions—especially concerning plasmid-mediated resistance and mobile genetic elements—are broadly transferable to other hospital-based AMR surveillance and experimental workflows.

Protocol Parameters

• Sample Selection: Prioritize isolates from high-risk departments (e.g., respiratory medicine) and specimen types (e.g., sputum) for surveillance or model establishment, following observed detection rates in the reference study.
• Antibiotic Susceptibility Testing: Employ broth microdilution protocols for multidrug resistance profiling, benchmarking against both carbapenem and third-generation cephalosporin antibiotics such as cefotaxime.
• Plasmid Conjugation Assays: Use standard recipient strains and confirm transfer events by PCR, as horizontal gene transfer rates can exceed 90% for certain CEGs.
• Genotype Analysis: Apply ERIC-PCR and cluster analysis software to identify and monitor the spread of dominant resistance genotypes in local cohorts.
• Mobile Element Screening: Incorporate multiplex PCR for common elements (e.g., ISEcp1, IS26) to profile genetic mobility factors in resistance studies.
• Workflow Note: When integrating cephalosporin antibiotics into selection or challenge protocols, ensure use of freshly prepared cefotaxime solutions for optimal activity, as recommended in the product information.

Research Support Resources

For researchers aiming to replicate or extend the workflows described in this and related studies, high-quality reagents are essential. Cefotaxime (SKU BA1012) from APExBIO is a third-generation cephalosporin antibiotic with proven stability and a robust spectrum of activity against both Gram-positive and Gram-negative bacteria. Its resistance to beta-lactamase enzymes makes it particularly valuable for antimicrobial resistance research and bacterial infection modeling. Proper storage and preparation are critical for maintaining efficacy, as outlined in the product documentation. Integrating such reagents supports rigorous, reproducible AMR research aligned with contemporary clinical and molecular findings.