Carbapenem-Resistant Enterobacter cloacae Complex in Southwest China: Molecular Characteristics and Risk Factors Caused by NDM Producers

Abstract

Purpose

The isolation rate of carbapenem-resistant Enterobacter cloacae complex (CREC) is continuously increasing. The aims of this study were to investigate the molecular characteristics and risk factors associated with CREC infections.

Methods

Bacterial species were identified using the matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) (Bruker Daltonik GmbH, Bremen, Germany), and the hsp60 gene was utilized for further typing. Antimicrobial susceptibilities were assessed through the MicroScan WalkAway 96 Plus system (Siemens, Germany) and the microbroth dilution method. Antimicrobial resistance genes were screened through polymerase chain reaction (PCR), while the homologous relationship was assessed using multilocus sequence typing (MLST). Conjugation experiments were performed to verify whether the plasmid could be transferred. Additionally, logistic regression model was employed to analyze risk factors for CREC infections.

Results

32 strains of CREC bacteria were isolated during the study, yet only 20 were retained for preservation. While the isolates demonstrated resistance to the majority of antibiotics, they exhibited high sensitivity to polymyxin B and tigecycline. All isolates carried the bla_NDM resistance gene, including 13 bla_NDM-1 isolates and 7 bla_NDM-5 isolates. MLST homology analysis revealed the presence of seven known ST types and one new ST type. Conjugation experiments confirmed that 13 isolates were capable of transferring the bla_NDM resistance gene to Escherichia coli strain EC600. Single-factor analysis identified multiple primary risk factors for CREC infection, but multivariate analysis did not reveal independent risk factors.

Conclusion

This study investigates the molecular characteristics and risk factors associated with CREC infections. The detection rate of CREC strains in our hospital is continuously rising and homology analysis suggested that strains might spread in our hospital, emphasizing the importance of implementing effective preventive measures to control the horizontal transmission of plasmid-mediated antimicrobial resistance genes.

Keywords:

• carbapenem-resistant
• Enterobacter cloacae complex
• antimicrobial resistance
• molecular characteristics
• risk factors

Data Sharing Statement

The data used or analyzed in this study can be obtained from the corresponding author upon reasonable request.

Ethics Approval and Consent to Participate

This study received approval from the Ethics Review Committee of the Affiliated Hospital of Southwest Medical University (KY2022267), in accordance with the principles outlined in the Declaration of Helsinki. Additionally, all patients participated by providing written informed consent.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

This work was supported by the grants from Sichuan Science and Technology Program (2022NSFSC1426, 2022ZHYZ0012, 2022YFQ0093, 2022YFS0008).