Characterizing and Tracking Carbapenemase Genes in CREC: Insights from Eight Hospitals in Guangdong (2022–2024)

Study Background and Research Question

Carbapenem-resistant Enterobacteriaceae (CRE) represent a significant global health challenge due to limited treatment options and rapid dissemination in healthcare settings. Among CRE, carbapenem-resistant Enterobacter cloacae (CREC) is increasingly prevalent, ranking third among CRE isolates in China. The COVID-19 pandemic has further complicated antimicrobial stewardship, with increased antibiotic use and healthcare disruptions contributing to the spread of multidrug-resistant organisms. Despite this, the molecular landscape and transmission dynamics of carbapenemase-encoding genes (CEGs) in CREC—particularly in the pandemic context—remain insufficiently characterized (Chen et al., 2025).

Key Innovation from the Reference Study

Chen et al. (2025) offer a comprehensive multicenter analysis of 54 CREC isolates from eight tertiary hospitals in Guangdong between December 2022 and June 2024. The study combines plasmid elimination, PCR assays, broth microdilution, and molecular typing to dissect the prevalence, genetic context, and transmissibility of CEGs. Notably, the work documents both chromosomal and plasmid localization of blaNDM-1, high rates of horizontal gene transfer, and the diversity of mobile genetic elements (MGEs) mediating resistance (Chen et al., 2025).

Methods and Experimental Design Insights

The investigators applied a robust combination of molecular and microbiological techniques:

• Sample Collection: 54 non-duplicate CREC isolates were obtained from eight teaching hospitals, representing diverse clinical departments and specimen types, with a predominance from respiratory medicine and sputum samples (Chen et al., 2025).
• Gene Detection and Localization: Variable temperature SDS plasmid elimination and PCR were used to identify and localize CEGs (including blaNDM-1, blaIMP, blaKPC-2) on plasmids and chromosomes.
• Antimicrobial Susceptibility: Broth microdilution was conducted to assess resistance profiles, including response to imipenem and other key antibiotics.
• Plasmid Conjugation: Mating experiments evaluated the transfer efficiency of CEG-harboring plasmids.
• MGE Identification: Six types of MGEs were screened, with ISEcp1 being the most frequent.
• Genotyping: ERIC-PCR and NTSYS clustering categorized isolates into 17 distinct genotypes, with types E and G being most prevalent.

Protocol Parameters

• assay | variable temperature SDS plasmid elimination | genetic localization of resistance determinants | enables differentiation between plasmid and chromosomal CEGs | paper
• assay | broth microdilution | quantitative MIC determination | standardized assessment of resistance to imipenem and comparators | paper
• assay | conjugation assay | transfer rate of CEGs (95.65%) | evaluates horizontal gene transfer potential | paper
• assay | PCR-based MGE screening | identification of 6 MGE types | clarifies genetic vehicles for CEG dissemination | paper
• assay | ERIC-PCR and NTSYS clustering | 17 genotypes identified | tracks clonal diversity and epidemiological spread | paper

Core Findings and Why They Matter

Chen et al. (2025) reveal several critical findings for antimicrobial resistance research:

• High Prevalence of CEGs: 85.19% of isolates harbored at least one CEG; blaNDM-1 was most common, present on both plasmids and chromosomes in 33.33% and exclusively on plasmids in 46.30% of isolates (Chen et al., 2025).
• Diverse Genetic Vehicles: Six MGE types were found, with ISEcp1 dominating (87.04%), and 40.74% of isolates carried four types simultaneously.
• Efficient Horizontal Transfer: Conjugation experiments showed a 95.65% transfer success rate for plasmid-borne CEGs, underscoring the risk of rapid dissemination in clinical settings.
• High Multidrug Resistance (MDR): CEG-positive strains exhibited greater resistance to imipenem, cefepime, gentamicin, ceftazidime/avibactam, ciprofloxacin, and levofloxacin than CEG-negative ones (P<0.05).
• Clonal Diversity: 17 genotypes were identified; types E and G were most common and distributed across multiple hospitals and departments, suggesting both clonal expansion and horizontal transfer.
• Epidemiological Patterns: Higher CEG detection rates were found in male and elderly patients, within respiratory medicine, and in sputum samples (64.81%, 72.22%, 20.37%, and 33.33%, respectively).

The findings highlight the dual challenge of MDR emergence and the rapid, mobile genetic spread of resistance determinants among gram-negative and gram-positive bacteria in hospital settings.

Comparison with Existing Internal Articles

Recent internal resources, such as the review "Imipenem: Advanced Applications in Multidrug Resistance and Immune Modulation" (internal article), discuss the mechanistic action of imipenem—a semisynthetic thienamycin antibiotic—against both gram-negative and gram-positive pathogens, focusing on beta-lactam antibiotic targeting PBPs and strategies to counteract emerging resistance. Chen et al. (2025) provide molecular epidemiology data that contextualize why such antibiotics may lose efficacy in the presence of transferable carbapenemase genes. The protocol-driven article "Imipenem (SKU P10075): Best Practices for Reproducible Antibacterial and Immune Modulation Studies" (internal article) gives workflow guidance for using imipenem in resistance and immune response assays. The current reference underscores the importance of considering CEG prevalence and transferability when designing such experiments, as genetic context strongly impacts resistance outcomes and assay interpretation. "Imipenem: Optimizing Antibacterial Research Workflows" (internal article) provides best practices for troubleshooting resistance modeling, which is directly informed by the diversity and transmissibility of CEGs observed in Chen et al. (2025).

Limitations and Transferability

Some limitations should be noted. The study is geographically restricted to Guangdong and may not capture CEG dynamics in other regions or settings with different antibiotic usage patterns. The sample size, while multicenter, is moderate, and the temporal window (2022–2024) captures only the most recent phase of the COVID-19 pandemic. Additionally, the study is observational; functional and in vivo consequences of the identified gene arrangements require further investigation (Chen et al., 2025). Nevertheless, the robust molecular characterization and conjugation assays provide transferable insights for surveillance, resistance modeling, and infection control in similar tertiary care environments. The work strongly supports the need to integrate genetic surveillance into antibacterial research and clinical stewardship strategies.

Research Support Resources

Researchers aiming to model multidrug resistance, investigate immune response modulation, or validate resistance mechanisms in vitro or in animal models can utilize well-characterized agents such as Imipenem (SKU P10075), a semisynthetic thienamycin antibiotic with validated activity against both gram-negative and gram-positive bacteria. APExBIO’s Imipenem is suitable for protocol-driven assays, including resistance profiling and immune modulation studies, as outlined in current workflow recommendations (internal article). Researchers should consider local prevalence and genetic context of carbapenemase-encoding genes, as revealed in the reviewed study, to optimize assay design and data interpretation.