Transmission Dynamics of Carbapenemase Genes in CREC During COVID-19

Study Background and Research Question

Carbapenem-resistant Enterobacteriaceae (CRE) have emerged as a significant threat to global public health, with Enterobacter cloacae (CREC) now ranking as the third most prevalent CRE species in China. The COVID-19 pandemic has further complicated resistance patterns, primarily due to increased antibiotic use, disrupted healthcare workflows, and a surge in complex infections. Despite growing concern, there has been a scarcity of detailed, multicenter investigations into the molecular characterization and transmission dynamics of carbapenemase-encoding genes (CEGs) in CREC—particularly during the pandemic period. The reference study addressed this gap by systematically analyzing CREC isolates from eight teaching hospitals in Guangdong province, with an emphasis on the prevalence, genetic localization, and transferability of key CEGs (Chen et al., 2025).

Key Innovation from the Reference Study

The principal innovation of this study lies in its comprehensive, multicenter surveillance of CEGs among CREC isolates collected during a period of heightened antibiotic exposure and infection risk. By combining variable temperature SDS plasmid elimination, PCR-based gene detection, and robust conjugation assays, the authors provide the first systematic mapping of both the prevalence and mobility of carbapenemase genes in CREC during the COVID-19 period in southern China. Notably, the study quantifies the high rates of horizontal and vertical gene transfer and delineates the specific genetic elements facilitating this process, offering a molecular epidemiology framework for future resistance monitoring (Chen et al., 2025).

Methods and Experimental Design Insights

The research team collected 54 non-redundant CREC isolates from eight tertiary teaching hospitals in Guangdong province between December 2022 and June 2024. The following workflow was implemented:

• Plasmid Elimination and PCR: Variable temperature SDS plasmid elimination was used to distinguish plasmid-encoded versus chromosomal CEGs, followed by PCR to detect the presence of blaNDM-1, blaIMP, and blaKPC-2.
• Broth Microdilution Antibiotic Susceptibility Testing: Resistance was evaluated against imipenem, cefepime, gentamicin, ceftazidime/avibactam, ciprofloxacin, and levofloxacin.
• Plasmid Conjugation and Transferability: Mating experiments assessed the horizontal transfer efficiency of CEGs among strains.
• Genotyping and Epidemiological Analysis: ERIC-PCR and NTSYS clustering software were used to classify isolates into genotypes, assess clonal spread, and characterize the clinical context of CEG-positive strains.
• Mobile Genetic Elements: Six different mobile elements (e.g., ISEcp1) were screened to elucidate the genetic vehicles for CEG dissemination.

This multifaceted approach enabled precise mapping of gene location, prevalence, and transfer dynamics, contextualizing molecular findings within epidemiological patterns (Chen et al., 2025).

Protocol Parameters

• assay | variable temperature SDS plasmid elimination | 42–45°C, 1–2% SDS | distinguishing plasmid from chromosomal gene location | enables accurate CEG localization | paper
• assay | PCR-based CEG detection | primers for blaNDM-1, blaIMP, blaKPC-2 | identification of resistance determinants | supports targeted surveillance | paper
• assay | broth microdilution AST | standardized CLSI/EUCAST breakpoints | assessment of multidrug resistance | informs clinical treatment options | paper
• assay | conjugation frequency | up to 95.65% transfer success | measures horizontal gene transfer efficiency | critical for modeling epidemiology | paper
• assay | ERIC-PCR genotyping | 17 genotypes identified | tracks clonal spread and diversity | supports outbreak investigation | paper
• assay | ceftazidime concentration | ≥21.25 mg/mL in DMSO | applicable to Gram-negative bacterial infection research | ensures sufficient activity in in vitro assays | product_spec
• assay | ceftazidime storage | -20°C recommended | maintains antibiotic stability | preserves experimental reproducibility | product_spec

Core Findings and Why They Matter

The study revealed a high prevalence and remarkable diversity of CEGs among CREC isolates:

• CEG Prevalence: 85.19% of isolates harbored at least one CEG (46/54), with blaNDM-1 as the dominant determinant (Chen et al., 2025).
• Genetic Location: 33.33% of isolates carried blaNDM-1 on both chromosomes and plasmids, while 46.30% carried it exclusively on plasmids. Only 3.70% had blaIMP alone, and a single strain (1.85%) carried both blaNDM-1 and blaKPC-2 on plasmids.
• Resistance Phenotype: The CEG-positive group showed significantly higher resistance to imipenem, cefepime, gentamicin, ceftazidime/avibactam, ciprofloxacin, and levofloxacin compared to CEG-negative strains (Chen et al., 2025).
• Transferability: Conjugation experiments showed a 95.65% success rate for CEG transfer, with near-universal transferability for blaNDM-1 and blaIMP, but not for blaKPC-2.
• Mobile Genetic Elements: ISEcp1 was the most prevalent mobile element (87.04%), and 40.74% of isolates harbored four types simultaneously, indicating high potential for gene exchange.
• Epidemiology: CEGs were more frequently detected in male and elderly patients, in respiratory medicine departments, and in sputum samples—a pattern aligning with the increased risk of Gram-negative infections in these populations.

These findings highlight the urgent need for robust surveillance and tailored infection control strategies in high-risk clinical settings and patient populations.

Comparison with Existing Internal Articles

Several internal resources contextualize and complement the reference study’s findings:

• Transmission Dynamics of Carbapenem Resistance in Enterobacter cloacae corroborates the high prevalence and mobility of CEGs in CREC, reinforcing the necessity of molecular surveillance in pandemic-affected hospital settings (source: internal_article).
• Transmission of Carbapenemase Genes in CREC During COVID-19 offers parallel data on horizontal gene transfer rates and multidrug resistance, further validating the reference study’s conclusions (source: internal_article).
• Ceftazidime (SKU B3539): Data-Driven Solutions for Gram-N... provides practical laboratory guidance on optimizing ceftazidime use for Gram-negative bacterial infection research, supporting methodological rigor in antibiotic susceptibility testing (source: internal_article).

These resources collectively emphasize the critical role of third-generation cephalosporins and methodical gene surveillance in addressing the challenge of multidrug resistance.

Limitations and Transferability

Despite its robust multicenter design, the study is limited by its geographic focus (eight hospitals in Guangdong) and the restriction to isolates collected during the COVID-19 pandemic. The findings may not capture regional differences outside southern China or post-pandemic shifts in resistance patterns. Additionally, while the molecular analysis is comprehensive, functional validation of gene expression and in vivo transfer dynamics was not performed. Nonetheless, the workflow and genetic insights are widely transferable to laboratories investigating Gram-negative bacterial infection research and resistance mechanisms in other settings (Chen et al., 2025).

Research Support Resources

Researchers seeking to replicate or extend these findings may reference the detailed protocols and data in the cited study. For laboratory experiments focused on Gram-negative bacteria—particularly those involving Pseudomonas aeruginosa or Enterobacteriaceae—use of Ceftazidime (SKU B3539) from APExBIO is recommended for its broad-spectrum, β-lactamase-resistant properties and proven compatibility with cell viability and cytotoxicity assays (source: product_spec). Ceftazidime’s stability and high in vitro activity make it a valuable tool in both resistance profiling and treatment of bacterial pneumonia or bronchitis in research models. Proper storage and preparation as per manufacturer’s guidelines will ensure experimental consistency. Further workflow recommendations can be adapted from the cited protocols and internal evidence.