陈瑞飞
阜外华中心血管病医院 检验科
The emergence of hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) was regarded as an emerging threat in clinical settings. Here, we investigated the prevalence of CRKP strains among inpatients in a new hospital over 1 year since its inception with various techniques, and carried out a WGS-based phylogenetic study to dissect the genomic background of these isolates. The genomes of three representative bla NDM-1-positive strains and the plasmids of four bla KPC-2-positive strains were selected for Nanopore long-read sequencing to resolve the complicated MDR structures. Thirty-five CRKP strains were identified from 193 K. pneumoniae isolates, among which 30 strains (85.7%) harbored bla KPC-2, whereas the remaining five strains (14.3%) were positive for bla NDM-1. The antimicrobial resistance profiles of bla NDM-1-positive isolates were narrower than that of bla KPC-2-positive isolates. Five isolates including two bla NDM-1-positive isolates and three bla KPC-2-positive strains could successfully transfer the carbapenem resistance phenotype by conjugation. All CRKP strains were categorized into six known multilocus sequence types, with ST11 being the most prevalent type. Phylogenetic analysis demonstrated that the clonal spread of ST11 bla KPC-2-positive isolates and local polyclonal spread of bla NDM-1-positive isolates have existed in the hospital. The bla NDM-1 gene was located on IncX3, IncFIB/IncHI1B, and IncHI5-like plasmids, of which IncFIB/IncHI1B plasmid has a novel structure. By contrast, all ST11 isolates shared the similar bla KPC-2-bearing plasmid backbone, and 11 of them possessed pLVPK-like plasmids. In addition, in silico virulome analysis, Galleria mellonella larvae infection assay, and siderophore secretion revealed the hypervirulence potential of most bla KPC-2-positive strains. Given that these isolates also had remarkable environmental adaptability, targeted measures should be implemented to prevent the grave consequences caused by hv-CRKP strains in nosocomial settings.
Frontiers in microbiology 2021
The spread of plasmid-mediated carbapenem-resistant clinical isolates is a serious threat to global health. In this study, an emerging NDM-encoding IncHI5-like plasmid from Klebsiella pneumoniae of infant patient origin was characterized, and the plasmid was compared to the available IncHI5-like plasmids to better understand the genetic composition and evolution of this emerging plasmid. Clinical isolate C39 was identified as K. pneumoniae and belonged to the ST37 and KL15 serotype. Whole genome sequencing (WGS) and analysis revealed that it harbored two plasmids, one of which was a large IncHI5-like plasmid pC39-334kb encoding a wide variety of antimicrobial resistance genes clustered in a single multidrug resistance (MDR) region. The bla NDM-1 gene was located on a ΔISAba125-bla NDM-1-ble MBL-trpF-dsbC structure. Comparative genomic analysis showed that it shared a similar backbone with four IncHI5-like plasmids and the IncHI5 plasmid pNDM-1-EC12, and these six plasmids differed from typical IncHI5 plasmids. The replication genes of IncHI5-like plasmids shared 97.06% (repHI5B) and 97.99% (repFIB-like) nucleotide identity with those of IncHI5 plasmids. Given that pNDM-1-EC12 and all IncHI5-like plasmids are closely related genetically, the occurrence of IncHI5-like plasmid is likely associated with the mutation of the replication genes of pNDM-1-EC12-like IncHI5 plasmids. All available IncHI5-like plasmids harbored 262 core genes encoding replication and maintenance functions and carried distinct MDR regions. Furthermore, 80% of them (4/5) were found in K. pneumoniae from Chinese nosocomial settings. To conclude, this study expands our knowledge of the evolution history of IncHI5-like plasmids, and more attention should be paid to track the evolution pathway of them among clinical, animal, and environmental settings.
Frontiers in cellular and infection microbiology 2021
Methylobacterium radiotolerans has only been identified in blood samples from end-stage renal failure or leukaemia patients in clinic. Here, we report a case of infective endocarditis (IE) caused by M. radiotolerans. 16S rRNA sequencing and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used to identify the bacteria isolated from cardiac vegetation. A drug sensitivity test was conducted by disk diffusion on blood Mueller-Hinton agar. This isolate was identified as M. radiotolerans, which was susceptible to aminoglycosides and ciprofloxacin. Our findings also suggest that M. radiotolerans can cause infection in a patient with normal immune function.
European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology 2020
