Emergence of mcr-8.2-harboring hypervirulent ST412 Klebsiella pneumoniae strain from pediatric sepsis: A comparative genomic survey

Characterization of a novel multi-resistant Pseudomonas juntendi strain from China with chromosomal blaVIM-2 and a megaplasmid coharboring blaIMP-1-like and blaOXA-1

BACKGROUND

Pseudomonas juntendi is a newly identified opportunistic pathogen, of which we have limited understanding. P. juntendi strains are often multidrug resistant, which complicates clinical management of infection.

METHODS

A strain of Pseudomonas juntendi (strain L4326) isolated from feces was characterized by MALDI-TOF-MS and Average Nucleotide Identity BLAST. This strain was further subject to whole-genome sequencing and Maximum Likelihood phylogenetic analysis. The strain was phenotypically characterized by antimicrobial susceptibility testing and conjugation assays.

RESULTS

We have isolated the novel P. juntendi strain L4236, which was multidrug resistant, but retained sensitivity to amikacin. L4236 harbored a megaplasmid that encoded blaOXA-1 and a novel blaIMP-1 resistance gene variant. P. juntendi strain L4236 was phylogenetically related to P. juntendi strain SAMN30525517.

CONCLUSION

A rare P. juntendi strain was isolated from human feces in southern China with a megaplasmid coharboring blaIMP-1-like and blaOXA-1. Antimicrobial selection pressures may have driven acquisition of drug-resistance gene mutations and carriage of the megaplasmid.

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

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.

ST11 KPC-2-Producing Klebsiella pneumoniae Isolated from Patient with Acute Myelocytic Leukemia

Background

The emergence of the ST11-CRKP (ST11-CRKP) strain is expected to become a serious public health problem in China. As one of the most serious complications in patients with acute myeloid lymphoma, infections can cause systemic infection and life-threatening sepsis, seriously affecting the morbidity, mortality, and quality of life of patients. Thus, ST11-CRKP infections in patients with acute myeloid lymphoma are worthy of our attention.

Aim

To investigate the occurrence and genetic characteristics of the ST11-CRKP from a patient with acute myeloid lymphoma.

Methods

Species identification was determined by MALDI-TOF MS. Antimicrobial susceptibility testing (AST) was conducted by VITEK 2 system with AST-N335 panel. Whole-genome sequencing was performed on the Illumina NovaSeq 6000 platform. Phylogenetic analyses were performed using Snippy based on the core-genome SNPs.

Findings

S1 nuclease pulsed-field gel electrophoresis (S1-PFGE), Southern blot and Whole-genome analysis indicated blaKPC-2 genes were located on plasmids with a conserved genetic environment. Moreover, the eight ST11-CRKP strains carry a variety of antimicrobial resistance genes (ARGs) and virulence factors. The ability of biofilm formation of eight strains was verified by a crystal violet assay. Core genome single-nucleotide polymorphism (cgSNP) analysis suggesting a possible bacterial translocation event.

Conclusion

We performed a comprehensive analysis of ST11-CRKP strains from a patient with acute myelocytic leukemia. Our study emphasized the need for continuous surveillance of ST11-CRKP in the clinic especially in the immunocompromised population.