Characterizing Carbapenemase Gene Transmission in Carbapenem-Resistant Enterobacter cloacae: Insights from a Multi-Hospital Survey in Guangdong

Study Background and Research Question

Carbapenem-resistant Enterobacteriaceae (CRE) represent an escalating global health concern, with Enterobacter cloacae ranking as the third most prevalent CRE species in China. The COVID-19 pandemic has intensified this challenge through increased antibiotic usage, care disruptions, and complex secondary infections. However, comprehensive investigation into the genetic mechanisms and transmission dynamics of carbapenemase-encoding genes (CEGs) in carbapenem-resistant E. cloacae (CREC) during this period has been lacking. This study addresses this gap by systematically analyzing the prevalence, localization, and transferability of CEGs among CREC strains across eight teaching hospitals in Guangdong province from December 2022 to June 2024 (Chen et al., 2025).

Key Innovation from the Reference Study

The study's chief innovation lies in its high-resolution mapping of CEG carriage and transmission in a sizeable, regionally diverse clinical cohort. By combining plasmid elimination, PCR-based gene detection, conjugation assays, and molecular typing, the authors provide a detailed portrait of the mechanisms enabling multidrug resistance in CREC. Notably, they demonstrate a strikingly high prevalence of plasmid-borne blaNDM-1 and its efficient horizontal transfer, which has critical consequences for infection control and future treatment strategies (Chen et al., 2025).

Methods and Experimental Design Insights

Fifty-four CREC isolates were collected from eight tertiary hospitals, with sampling spanning both respiratory and other clinical departments. The variable temperature Sodium Dodecyl Sulfate (SDS) plasmid elimination method enabled differentiation of chromosomal versus plasmid localization of CEGs. PCR amplification targeted blaNDM-1, blaIMP, and blaKPC-2 genes. Broth microdilution assays assessed resistance profiles to key antimicrobials including imipenem, cefepime, gentamicin, ceftazidime/avibactam, ciprofloxacin, and levofloxacin. Plasmid conjugation experiments measured the horizontal transferability of resistance genes, while ERIC-PCR and NTSYS software enabled detailed genotypic clustering (Chen et al., 2025).

Protocol Parameters

• plasmid elimination assay | variable temperature SDS | CREC isolates | Differentiates plasmid vs chromosomal gene localization | paper
• PCR detection | target: blaNDM-1, blaIMP, blaKPC-2 | CREC isolates | Identifies key resistance determinants | paper
• antimicrobial susceptibility | broth microdilution | imipenem, cefepime, gentamicin, ceftazidime/avibactam, ciprofloxacin, levofloxacin | Quantifies resistance phenotypes | paper
• conjugation experiment | filter mating protocol | CEG-positive strains | Measures horizontal gene transfer rates | paper
• ERIC-PCR genotyping | custom primer set | 54 CREC strains | Establishes genetic relatedness and epidemiology | paper
• Research workflows using third-generation cephalosporins such as ceftazidime | 3–6 g/day in divided doses (clinical reference); in vitro: ≥21.25 mg/mL in DMSO, storage at -20°C | Gram-negative infection models | Recommended for β-lactamase-resistant phenotype validation | workflow_recommendation (product_spec)

Core Findings and Why They Matter

Among the 54 CREC isolates, 85.19% harbored at least one carbapenemase-encoding gene (CEG). The blaNDM-1 gene was the most prevalent, found on both chromosomes and plasmids in 33.33% of strains and exclusively on plasmids in 46.30%. A minority carried blaIMP (3.70%) or both blaNDM-1 and blaKPC-2 (1.85%) on plasmids (Chen et al., 2025). Notably, the CEG-positive group exhibited significantly higher resistance rates to multiple antibiotics, including ceftazidime/avibactam, underscoring the clinical challenge posed by these strains. Plasmid conjugation experiments achieved a 95.65% overall success rate for CEG transfer, with nearly universal transferability for blaNDM-1 and blaIMP, highlighting the potential for rapid horizontal dissemination. The identification of six mobile genetic element types, particularly ISEcp1 (87.04%), further confirms the genetic flexibility underpinning this resistance (Chen et al., 2025). Demographically, CEGs were detected most frequently in male and elderly patients, with respiratory medicine departments and sputum samples representing the primary clinical contexts. Genotypic analysis revealed 17 CREC lineages, with two (type E and G) dominating across multiple hospitals, suggesting both intra- and inter-hospital transmission.

Comparison with Existing Internal Articles

Several internal resources address the challenges of Gram-negative bacterial infection research, particularly involving third-generation cephalosporins like ceftazidime. For instance, "Ceftazidime and the Future of Gram-Negative Infection Research" explores ceftazidime's role as a β-lactamase-resistant agent and its significance in the post-pandemic resistance landscape. The current study aligns with these themes, emphasizing the urgent need for robust, β-lactamase-resistant antibiotics and research tools to combat emerging multidrug-resistant strains. The article "Ceftazidime (SKU B3539): Data-Driven Solutions for Gram-Negative Research" provides practical workflow insights for deploying ceftazidime in experimental settings, complementing the reference study's focus on resistance mechanism elucidation. Finally, "Ceftazidime: Third-Generation Cephalosporin for Gram-Negative Research" offers detailed guidance on mechanism, benchmarks, and real-world research integration, echoing the reference paper's emphasis on molecular surveillance and genotype-driven infection control.

Limitations and Transferability

This study offers a geographically detailed snapshot but is limited by its regional focus on Guangdong province and sampling timeframe (2022–2024). The relatively small sample size (n=54) and lack of direct clinical outcome data constrain broad generalization. Furthermore, while plasmid and chromosomal gene carriage was mapped via robust molecular methods, functional studies on in vivo virulence or transmission were outside the scope. Transferability to other settings should be approached cautiously, with attention to local epidemiology and resistance landscapes. Nevertheless, the molecular techniques and analytic frameworks described are broadly applicable to Gram-negative bacterial infection research, especially for those investigating β-lactamase-resistant phenotypes or pandemic-era resistance dynamics (Chen et al., 2025).

Research Support Resources

Researchers aiming to model Gram-negative resistance or screen for β-lactamase activity can utilize robust laboratory agents such as Ceftazidime (SKU B3539), a third-generation cephalosporin with high activity against Pseudomonas aeruginosa and proven resistance to β-lactamase hydrolysis (product_spec). Ceftazidime’s well-characterized properties and recommended storage/handling protocols support reliable, reproducible workflows in the study of multidrug-resistant Enterobacteriaceae and related pathogens. For further workflow optimization, established internal guides and product specifications are available to inform experimental design and data interpretation.