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. 2024 Jun 4:17:2273-2283.
doi: 10.2147/IDR.S461118. eCollection 2024.

Emergence of an Extensive Drug Resistant Citrobacter portucalensis Clinical Strain Harboring bla SFO-1, bla KPC-2, and bla NDM-1

Kexin Guo #  1 , Zanzan Zhao #  1 , Yu Yang  1 , Xiawei Jiang  1 , Hao Xu  2 , Fangfang Tao  1 , Ye Xu  1 , Wenhong Liu  1
Affiliations

Emergence of an Extensive Drug Resistant Citrobacter portucalensis Clinical Strain Harboring bla SFO-1, bla KPC-2, and bla NDM-1

Kexin Guo et al. Infect Drug Resist. .

Abstract

Background: To explore the plasmid characteristics and transfer mechanisms of an extensive drug resistant (XDR) clinical isolate, Citrobacter portucalensis L2724hy, co-producing bla SFO-1, bla NDM-1, and bla KPC-2.

Methods: Species confirmation of L2724hy was achieved through 16S rRNA sequencing and Average Nucleotide Identity (ANI) analysis. Antimicrobial susceptibility testing (AST) employed the agar dilution and micro broth dilution methods. Identification of resistance genes was carried out by PCR and whole-genome sequencing (WGS). Essential resistance gene locations were verified by S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and southern hybridization experiments. Subsequent WGS data analysis delved into drug resistance genes and plasmids.

Results: The confirmation of the strain L2724hy as an extensive drug-resistant Citrobacter portucalensis, resistant to almost all antibiotics tested except polymyxin B and tigecycline, was achieved through 16S rRNA sequencing, ANI analysis and AST results. WGS and subsequent analysis revealed L2724hy carrying bla SFO-1, bla NDM-1, and bla KPC-2 on plasmids of various sizes. The uncommon ESBL gene bla SFO-1 coexists with the fosA3 gene on an IncFII plasmid, featuring the genetic environment IS26-fosA3-IS26-ampR-bla SFO-1-IS26. The bla NDM-1 was found on an IncX3 plasmid, coexisting with bla SHV-12, displaying the sequence IS5-IS3000-IS3000-Tn2-bla NDM-1-ble-trpF-dsbD-cutA-gros-groL, lacking ISAa125. The bla KPC-2 is located on an unclassified plasmid, exhibiting the sequence Tn2-tnpR-ISKpn27-bla KPC-2-ISKpn6-korC. Conjugation assays confirmed the transferability of both bla NDM-1 and bla KPC-2.

Conclusion: We discovered the coexistence of bla SFO-1, bla NDM-1, and bla KPC-2 in C. portucalensis for the first time, delving into plasmid characteristics and transfer mechanisms. Our finding highlights the importance of vigilant monitoring of drug-resistance genes and insertion elements in uncommon strains.

Keywords: Citrobacter spp; IncFII; XDR; blaKPC; blaNDM; blaSFO.

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Conflict of interest statement

The authors report no conflicts of interest in this work.

Figures

Figure 1
Figure 1
S1-PFGE profiles and southern blotting hybridization for L2724hy. S1-PFGE determines the number and size of plasmids in the strain. Southern blotting hybridization indicates the location of resistance genes blaSFO-1, blaNDM-1, and blaKPC-2.
Figure 2
Figure 2
Comparative analysis of plasmids p2-L2724hy-SFO-1, p4-L2724hy-NDM-1, and p5-L2724hy-KPC-2 in L2724hy. The BRIG circle maps show plasmid resistance genes and mobile genetic elements (MGEs). (a) plasmid p2-L2724hy-SFO-1 carrying blaSFO-1 and fosA3. (b) plasmid p4-L2724hy-NDM-1 harboring blaNDM-1 and blaSHV-12. (c) plasmid p5-L2724hy-KPC-2 bearing blaKPC-2.
Figure 3
Figure 3
Genetic environment of blaSFO-1, blaNDM-1, and blaKPC-2 in L2724hy. (a) blaSFO-1 (b) blaNDM-1 (c) blaKPC-2. Red arrows denote drug resistance genes, green arrows denote transposons, pink arrows denote other genes, and yellow arrows represent hypothetical proteins.
Figure 4
Figure 4
A conjugative plasmid p2-L2724hy-SFO-1. ORF1-57,fosA3; ORF1-60, blaSFO-1.
See this image and copyright information in PMC

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