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    • Carbapenemase Gene Dynamics in Multidrug-Resistant E. cloaca

    2026-05-09

    Carbapenemase Gene Dynamics in Multidrug-Resistant Enterobacter cloacae: Insights from a Multicenter Genomic Survey

    Study Background and Research Question

    Carbapenem-resistant Enterobacteriaceae (CRE) constitute a critical global health threat, with Enterobacter cloacae (CREC) ranking among the top three CRE in China. The COVID-19 pandemic, with its associated increase in antibiotic use and healthcare disruptions, has further complicated the epidemiology of antimicrobial resistance. However, detailed molecular epidemiology of carbapenemase-encoding genes (CEGs) in CREC, particularly in the context of pandemic-driven pressures, has been lacking. The present study by Chen et al. addresses this gap by investigating the prevalence, genetic context, and transmission dynamics of CEGs in CREC isolates from eight major teaching hospitals in Guangdong Province between December 2022 and June 2024 (Chen et al., 2025).

    Key Innovation from the Reference Study

    The principal innovation of this work lies in its comprehensive, multicenter genomic and phenotypic characterization of CEGs in CREC during a period of heightened antibiotic pressure. By integrating plasmid elimination, PCR, conjugation experiments, and genotyping (ERIC-PCR), the study elucidates both the genetic vehicles (plasmids vs. chromosomes) and the mobility of key resistance determinants—most notably blaNDM−1. The investigation further contextualizes these findings within clinical epidemiology, correlating CEG carriage with patient demographics and sample sources (Chen et al., 2025).

    Methods and Experimental Design Insights

    A total of 54 carbapenem-resistant E. cloacae isolates were collected from diverse departments across eight tertiary hospitals. The study employed variable temperature Sodium Dodecyl Sulfate (SDS) plasmid elimination to distinguish plasmid-borne from chromosomal genes, followed by PCR for precise CEG detection and localization. Antimicrobial susceptibility was quantitatively assessed using the broth microdilution method. Conjugation experiments evaluated the transferability of resistance plasmids. ERIC-PCR and cluster analysis with NTSYS software were applied to genotype strains and explore epidemiological links within and between hospitals (Chen et al., 2025).

    Protocol Parameters

    • isolate screening | 54 isolates | multicenter hospital surveillance | ensures broad epidemiological representation | paper
    • plasmid elimination (SDS) | variable temperature | gene localization assay | distinguishes plasmid vs. chromosomal CEGs | paper
    • PCR detection | gene-specific primers | CEG identification | precise assignment of blaNDM−1, blaIMP, blaKPC−2 | paper
    • broth microdilution | CLSI standards | antimicrobial susceptibility | quantitative resistance profiling | paper
    • ERIC-PCR | standardized protocol | strain genotyping | tracks clonal relationships | paper
    • conjugation assay | standard mating protocol | horizontal gene transfer assessment | measures transmissibility of resistance | paper

    Core Findings and Why They Matter

    The study found a strikingly high prevalence (85.19%) of CEGs among CREC isolates. The blaNDM−1 gene was the dominant resistance determinant, detected on both plasmids and chromosomes in 33.33% of isolates and exclusively on plasmids in 46.30%. Minor fractions carried only blaIMP or both blaNDM−1 and blaKPC−2 on plasmids (Chen et al., 2025). Antimicrobial susceptibility testing revealed that CEG-positive isolates exhibited significantly elevated resistance rates to imipenem, cefepime, gentamicin, ceftazidime/avibactam, ciprofloxacin, and levofloxacin compared to CEG-negative isolates (P<0.05; Chen et al., 2025). Notably, the resistance profile directly implicates the clinical challenge of treating CREC infections, as many standard-of-care agents—including synthetic fluoroquinolone antibiotics like levofloxacin—may be rendered ineffective in the presence of CEGs. Plasmid conjugation experiments demonstrated a high transferability of CEGs, with an overall 95.65% success rate. The transfer frequency for blaNDM−1 was 95.45%, for blaIMP 100%, and for blaKPC−2 0%, highlighting both the ease of horizontal dissemination for most CEGs and the apparent immobility of certain resistance determinants (Chen et al., 2025). Six types of mobile genetic elements were characterized, with ISEcp1 being the most prevalent (87.04%). CREC strains frequently carried multiple mobile elements, and four types co-occurred in 40.74% of isolates, underscoring the genetic complexity and adaptability of these pathogens. Genotypic analysis divided the isolates into 17 groups, revealing interdepartmental and interhospital spread, with certain genotypes (E and G) predominating. Epidemiologically, CEGs were more frequently detected in males, elderly patients, those in respiratory medicine, and in sputum samples, suggesting patient and specimen risk factors for resistance propagation.

    Comparison with Existing Internal Articles

    Recent internal reviews have explored the mechanistic and translational aspects of levofloxacin and other synthetic fluoroquinolone antibiotics in the context of bacterial DNA replication pathway inhibition (Levofloxacin at the Translational Frontier). These articles emphasize the compound’s dual role as a DNA gyrase inhibitor and as a tool for osteoblast growth inhibition assays and calcium deposition inhibition studies. The current reference study, however, highlights the challenge posed by multidrug-resistant CREC, where even robust agents like levofloxacin can lose efficacy due to widespread CEG carriage. This underscores the need for both innovative antimicrobial strategies and careful resistance monitoring, as discussed in Levofloxacin (SKU B1959): Reproducible Solutions for Cell..., which provides workflow guidance for optimizing experimental outcomes with existing antibiotics.

    Limitations and Transferability

    While the study’s multicenter design and integration of molecular, phenotypic, and epidemiological data offer significant strengths, several limitations exist. The geographic focus on Guangdong Province may limit generalizability to other regions or healthcare settings with differing resistance pressures. The sample size, though reasonable for a multicenter study, may not capture rare genotypes or resistance mechanisms. Additionally, the study primarily addresses CEGs and does not comprehensively assess non-carbapenemase resistance pathways. Finally, while the experimental design robustly demonstrates in vitro transferability and distribution, clinical outcomes and patient-level risk factors warrant further investigation (Chen et al., 2025).

    Research Support Resources

    For researchers aiming to further investigate multidrug resistance mechanisms—such as those involving bacterial DNA replication pathway inhibition, osteoblast growth inhibition assays, or chondrocyte glycosaminoglycan synthesis studies—well-characterized compounds are essential. Levofloxacin (SKU B1959), a synthetic fluoroquinolone antibiotic available from APExBIO, offers standardized activity as a DNA gyrase inhibitor for both antibacterial and bone/cell biology research workflows (workflow_recommendation). Proper selection of reagents and rigorous experimental controls are necessary to model resistance as observed in contemporary clinical isolates. For further assay optimization and translational research perspectives, readers may consult internal resources such as Levofloxacin at the Frontiers of Antibacterial and Bone Metabolism Research (workflow_recommendation).