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Published on: March 9, 2016
Detection of IMP-4 and SFO-1 co-producing ST51 Enterobacter hormaechei clinical isolates
Jie Qiao1,2, Haoyu Ge1,2, Hao Xu2
1Department of Laboratory Medicine, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.
Purpose:
To explore the genetic characteristics of the IMP-4 and SFO-1 co-producing multidrug-resistant (MDR) clinical isolates, Enterobacter hormaechei YQ13422hy and YQ13530hy.
Methods:
MALDI-TOF MS was used for species identification. Antibiotic resistance genes (ARGs) were tested by PCR and Sanger sequencing analysis. In addition to agar dilution, broth microdilution was used for antimicrobial susceptibility testing (AST). Whole-genome sequencing (WGS) analysis was conducted using the Illumina NovaSeq 6000 and Oxford Nanopore platforms. Annotation was performed by RAST on the genome. The phylogenetic tree was achieved using kSNP3.0. Plasmid characterization was conducted using S1-pulsed-field gel electrophoresis (S1-PFGE), Southern blotting, conjugation experiments, and whole genome sequencing (WGS). An in-depth study of the conjugation module was conducted using the OriTFinder website. The genetic context of bla IMP-4 and bla SFO-1 was analyzed using BLAST Ring Image Generator (BRIG) and Easyfig 2.3.
Results:
YQ13422hy and YQ13530hy, two MDR strains of ST51 E. hormaechei harboring bla IMP-4 and bla SFO-1, were identified. They were only sensitive to meropenem, amikacin and polymyxin B, and were resistant to cephalosporins, aztreonam, piperacillin/tazobactam and aminoglycosides, intermediate to imipenem. The genetic context surrounding bla IMP-4 was 5'CS-hin-1-IS26-IntI1-bla IMP-4-IS6100-ecoRII. The integron of bla IMP-4 is In823, which is the array of gene cassettes of 5'CS-bla IMP-4. Phylogenetic analysis demonstrated that E. hormaechei YQ13422hy and YQ13530hy belonged to the same small clusters with a high degree of homology.
Conclusion:
This observation revealed the dissemination of the bla IMP-4 gene in E. hormaechei in China. We found that bla IMP-4 and bla SFO-1 co-exist in MDR clinical E. hormaechei isolates. This work showed a transferable IncN-type plasmid carrying the bla IMP-4 resistance gene in E. hormaechei. We examined the potential resistance mechanisms of pYQ13422-IMP-4 and pYQ13422-SFO-1, along with their detailed genetic contexts.
Insights
Two multidrug-resistant Enterobacter hormaechei strains co-harbored IMP-4 and SFO-1 resistance genes. These genes were found on a transferable IncN-type plasmid, indicating potential spread of antibiotic resistance.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Multidrug-resistant (MDR) clinical isolates pose a significant threat to public health.
- Enterobacter hormaechei is an opportunistic pathogen known for acquiring antibiotic resistance.
Purpose of the Study:
- To investigate the genetic basis of IMP-4 and SFO-1 co-production in MDR Enterobacter hormaechei clinical isolates.
- To characterize the genetic context and mobile genetic elements associated with these resistance genes.
Main Methods:
- Species identification using MALDI-TOF MS.
- Antibiotic resistance gene detection via PCR and Sanger sequencing.
- Antimicrobial susceptibility testing using broth microdilution and agar dilution.
- Whole-genome sequencing (WGS) on Illumina NovaSeq 6000 and Oxford Nanopore platforms.
- Plasmid characterization through S1-PFGE, Southern blotting, and conjugation experiments.
Main Results:
- Two MDR Enterobacter hormaechei strains (YQ13422hy and YQ13530hy) of ST51 were identified, co-harboring bla_IMP-4 and bla_SFO-1.
- These isolates were resistant to multiple antibiotics, with sensitivity only to meropenem, amikacin, and polymyxin B.
- The genetic context of bla_IMP-4 was elucidated as 5'CS-hin-1-IS26-In tI1-bla_IMP-4-IS6100-ecoRII, with the integron In823.
- Phylogenetic analysis confirmed high homology between the two isolates, belonging to the same cluster.
Conclusions:
- The study identified MDR Enterobacter hormaechei isolates co-producing IMP-4 and SFO-1 in China.
- A transferable IncN-type plasmid carrying the bla_IMP-4 gene was identified in these isolates.
- Detailed analysis of the genetic contexts of bla_IMP-4 and bla_SFO-1 on plasmids pYQ13422-IMP-4 and pYQ13422-SFO-1 was performed.
