Carriage of distinct blaKPC-2 and blaOXA-48 plasmids in a single ST11 hypervirulent Klebsiella pneumoniae isolate in Egypt

Virulence Factors and Carbapenem-Resistance Mechanisms in Hypervirulent Klebsiella Pneumoniae

Hypervirulent Klebsiella pneumoniae (hvKP) has emerged as a novel variant of K. pneumoniae, exhibiting distinct phenotypic and genotypic characteristics that confer increased virulence and pathogenicity. It is not only responsible for nosocomial infections but also community-acquired infections, including liver abscesses, endophthalmitis, and meningitis, leading to significant morbidity and mortality. HvKP has been reported all over the world, but it is mainly prevalent in Asia Pacific, especially China. Moreover, hvKP can acquire carbapenemase genes resulting in the emergence of carbapenem-resistant hypervirulent K. pneumoniae (CR-hvKP), which possesses both high virulence and drug resistance capabilities. Consequently, CR-hvKP poses substantial challenges to infection control and presents serious threats to global public health. In this paper, we provide a comprehensive summary of the epidemiological characteristics, virulence factors, and mechanisms underlying carbapenem resistance in hvKP strains with the aim of offering valuable insights for practical prevention strategies as well as future research.

Klebsiella pneumoniae ST147 harboring blaNDM-1, multidrug resistance and hypervirulence plasmids

The spread of hypervirulent (hv) and carbapenem-/multidrug-resistant Klebsiella pneumoniae is an emerging problem in healthcare settings. The New Delhi metallo-β-lactamase-1 (blaNDM-1) is found in Enterobacteriaceae including K. pneumoniae. The blaNDM-1 is capable of hydrolyzing β-lactam antibiotics which are used for treatment of severe infections caused by multidrug-resistant Gram-negative bacteria. This is associated with the unacceptably high mortality rate in immunocompromised burn injury patients. This study reports on the characterization of blaNDM-1 gene and virulence factors in hv carbapenem-/multidrug-resistant K. pneumoniae ST147 in the burns unit of a tertiary teaching hospital during routine surveillance. Two K. pneumoniae strains were obtained from wounds of burn-infected patients from May 2020 to July 2021. The hypervirulence genes and genetic context of the blaNDM-1 gene and mobile genetic elements potentially involved in the transposition of the gene were analyzed. We identified a conserved genetic background and an IS26 and open reading frame flanking the blaNDM-1 gene that could suggest its involvement in the mobilization of the gene. The plasmid harbored additional antibiotic resistance predicted regions that were responsible for resistance to almost all the routinely used antibiotics. To ensure the identification of potential outbreak strains during routine surveillance, investigations on resistance genes and their environment in relation to evolution are necessary for molecular epidemiology.IMPORTANCEData obtained from this study will aid in the prompt identification of disease outbreaks including evolving resistance and virulence of the outbreak bacteria. This will help establish and implement antimicrobial stewardship programs and infection prevention protocols in fragile health systems in countries with limited resources. Integration of molecular surveillance and translation of whole-genome sequencing in routine diagnosis will provide valuable data for control of infection. This study reports for the first time a high-risk clone K. pneumoniae ST147 with hypervirulence and multidrug-resistance features in Ghana.

Comparative genomic analysis of strong biofilm-forming Klebsiella pneumoniae isolates uncovers novel ISEcp1-mediated chromosomal integration of a full plasmid-like sequence

BACKGROUND

The goal of the current study was to elucidate the genomic background of biofilm formation in Klebsiella pneumoniae.

METHODS

Clinical isolates were screened for biofilm formation using the crystal violet assay. Antimicrobial resistance (AMR) profiles were assessed by disk diffusion and broth microdilution tests. Biofilm formation was correlated to virulence and resistance genes screened by PCR. Draft genomes of three isolates that form strong biofilm were generated by Illumina sequencing.

RESULTS

Only the siderophore-coding gene iutA was significantly associated with more pronounced biofilm formation. ST1399-KL43-O1/O2v1 and ST11-KL15-O4 were assigned to the multidrug-resistant strain K21 and the extensively drug-resistant strain K237, respectively. ST1999-KL38-O12 was assigned to K57. Correlated with CRISPR/Cas distribution, more plasmid replicons and prophage sequences were identified in K21 and K237 compared to K57. The acquired AMR genes (blaOXA-48, rmtF, aac(6')-Ib and qnrB) and (blaNDM-1, blaCTX-M, aph(3')-VI, qnrS, and aac(6')-Ib-cr) were found in K237 and K21, respectively. The latter showed a novel ISEcp1-mediated chromosomal integration of replicon type IncM1 plasmid-like structure harboring blaCTX-M-14 and aph(3')-VI that uniquely interrupted rcsC. The plasmid-mediated heavy metal resistance genes merACDEPRT and arsABCDR were spotted in K21, which also exclusively carried the acquired virulence genes mrkABCDF and the hypervirulence-associated genes iucABCD-iutA, and rmpA/A2. Pangenome analysis revealed NTUH-K2044 accessory genes most frequently shared with K21.

CONCLUSIONS

While less virulent to Galleria mellonella than ST1999 (K57), the strong biofilm former, multidrug-resistant, NDM-producer K. pneumoniae K21 (ST1399-KL43-O1/O2v1) carries a novel chromosomally integrated plasmid-like structure and hypervirulence-associated genes and represents a serious threat to countries in the area.

The dynamic evolution and IS26-mediated interspecies transfer of a blaNDM-1-bearing fusion plasmid leading to a hypervirulent carbapenem-resistant Klebsiella pneumoniae strain harbouring blaKPC-2 in a single patient

OBJECTIVES

To characterize the evolution and interspecies transfer of plasmids between Klebsiella pneumoniae and Escherichia coli within a single patient.

METHODS

Minimum inhibitory concentrations were measured using broth microdilution assays. Conjugation assays, string tests, and Galleria mellonella infection model experiments were also conducted. Whole-genome sequencing was performed on the Illumina and Nanopore platforms. Antimicrobial resistance determinants, insertion sequences, and virulence factors were identified using ABRicate/ResFinder database, ISFinder, and virulence factor database. Wzi and capsular polysaccharide (KL) were typed using Kleborate and Kaptive. Multi-locus sequence typing (MLST), replicon typing, and single nucleotide polymorphism analyses were conducted using the BacWGSTdb server.

RESULTS

The carbapenem-resistant K. pneumoniae 2111KP was characterized as ST11, wzi64, and KL64, with a positive string test result and a relatively high virulence phenotype. Analysis of the 2111KP genome revealed that blaNDM-1 was located in a 268,400-bp IncFIB/IncHI1B/IncX3 conjugative plasmid (p2111KP-1), regulated by IS26, IS5, and ISKox3. p2111KP-1 was also a rmpA2-associated virulence plasmid with an iutA-iucABCD gene cluster and a IS26-mediated multidrug-resistant fusion plasmid, which contained 8-bp (AGCTGCAC or GGCCTTTG) target site duplications. Segments flanked by IS26 of p2111KP-1 were 99.99% identical to a 49,016-bp E. coli plasmid.

CONCLUSIONS

This study provided direct evidence of plasmid fusion via IS26 between two different bacterial species within one patient and revealed the process by which genetic elements conferring carbapenem resistance and virulence were simultaneously transferred between these species. It highlights the need for strategic antibiotic use and rigorous monitoring to prevent the plasmid-mediated fusion and transmission of drug-resistance/virulence factors.

The origin and evolution of IncF33 plasmids based on large-scale data sets

IMPORTANCE

Plasmids that capture multiple antibiotic resistance genes are spreading widely, leading to the emergence and prevalence of multidrug-resistant bacteria. IncF33 plasmids are a newly emerged plasmid type highly prevalent in animal-source Enterobacterales in China, and they are important vectors for transmitting several clinically important antibiotic resistance genes. The study revealed that the IncF33 plasmid is mainly prevalent in China animal-derived Escherichia coli and has the potential for cointegration and intercontinental dissemination. Therefore, it is crucial to enhance surveillance and control measures to limit the spread of IncF33 plasmids and their associated antibiotic resistance genes.

Impact of COVID-19 pandemic on profiles of antibiotic-resistant genes and bacteria in hospital wastewater

The COVID-19 pandemic has severely affected healthcare worldwide and has led to the excessive use of disinfectants and antimicrobial agents. However, the impact of excessive disinfection measures and specific medication prescriptions on the development and dissemination of bacterial drug resistance during the pandemic remains unclear. This study investigated the influence of the pandemic on the composition of antibiotics, antibiotic resistance genes (ARGs), and pathogenic communities in hospital wastewater using ultra-performance liquid chromatography-tandem mass spectrometry and metagenome sequencing. The overall level of antibiotics decreased after the COVID-19 outbreak, whereas the abundance of various ARGs increased in hospital wastewater. After COVID-19 outbreak, blaOXA, sul2, tetX, and qnrS had higher concentrations in winter than in summer. Seasonal factors and the COVID-19 pandemic have affected the microbial structure in wastewater, especially of Klebsiella, Escherichia, Aeromonas, and Acinetobacter. Further analysis revealed the co-existence of qnrS, blaNDM, and blaKPC during the pandemic. Various ARGs significantly correlated with mobile genetic elements, implying their potential mobility. A network analysis revealed that many pathogenic bacteria (Klebsiella, Escherichia, and Vibrio) were correlated with ARGs, indicating the existence of multi-drug resistant pathogens. Although the calculated resistome risk score did not change significantly, our results suggest that the COVID-19 pandemic shifted the composition of residual antibiotics and ARGs in hospital wastewater and contributed to the dissemination of bacterial drug resistance.

Molecular typing methods & resistance mechanisms of MDR Klebsiella pneumoniae

The emergence and transmission of carbapenem-resistant Klebsiella pneumoniae (CRKP) have been recognized as a major public health concern. Here, we investigated the molecular epidemiology and its correlation with the mechanisms of resistance in CRKP isolates by compiling studies on the molecular epidemiology of CRKP strains worldwide. CRKP is increasing worldwide, with poorly characterized epidemiology in many parts of the world. Biofilm formation, high efflux pump gene expression, elevated rates of resistance, and the presence of different virulence factors in various clones of K. pneumoniae strains are important health concerns in clinical settings. A wide range of techniques has been implemented to study the global epidemiology of CRKP, such as conjugation assays, 16S-23S rDNA, string tests, capsular genotyping, multilocus sequence typing, whole-genome sequencing-based surveys, sequence-based PCR, and pulsed-field gel electrophoresis. There is an urgent need to conduct global epidemiological studies on multidrug-resistant infections of K. pneumoniae across all healthcare institutions worldwide to develop infection prevention and control strategies. In this review, we discuss different typing methods and resistance mechanisms to explore the epidemiology of K. pneumoniae pertaining to human infections.

Epidemiological characteristics and molecular evolution mechanisms of carbapenem-resistant hypervirulent Klebsiella pneumoniae

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP), a type of Klebsiella pneumoniae (KP) that exhibits hypervirulence and carbapenem resistance phenotypes, can cause severe infections, both hospital- and community-acquired infections. CR-hvKP has brought great challenges to global public health and is associated with significant morbidity and mortality. There are many mechanisms responsible for the evolution of the hypervirulence and carbapenem resistance phenotypes, such as the horizontal transfer of the plasmid carrying the carbapenem resistance gene to hypervirulent Klebsiella pneumoniae (hvKP) or carbapenemase-producing Klebsiella pneumoniae (CRKP) acquiring a hypervirulence plasmid carrying a virulence-encoding gene. Notably, KP can evolve into CR-hvKP by acquiring a hybrid plasmid carrying both the carbapenem resistance and hypervirulence genes. In this review, we summarize the evolutionary mechanisms of resistance and plasmid-borne virulence as well as the prevalence of CR-hvKP.

Co-occurrence of dual carbapenemases KPC-2 and OXA-48 with the mobile colistin resistance gene mcr-9.1 in Enterobacter xiangfangensis

Bacterial infections with the genus Enterobacter are notoriously difficult to treat and often associated with resistance to penicillin, aminoglycosides, fluoroquinolones, and third-generation cephalosporins. Also, Enterobacter species have emerged as the third most common hosts for carbapenemases worldwide, forcing the use of colistin as a “last-resort” antibiotic for the treatment. Studies on the population structure of the genus Enterobacter repeatedly detect E. xiangfangensis as a common clinical species present worldwide. Here, we report on the characteristics of an extreme drug-resistant E. xiangfangensis isolate va18651 (ST88), obtained from a cervical swab of an expectant mother. The isolate was resistant to almost all the classes of antibiotics tested, including β-lactams (viz., penicillins, carbapenems, cephalosporin, monobactams, and their combinations), quinolone, aminoglycosides, and sulfonamide/dihydrofolate reductase inhibitor, and exhibited heteroresistance towards colistin. Analysis of its complete genome sequence revealed 37 antibiotic resistance genes (ARGs), including mcr-9.1, bla_KPC-2, and bla_OXA-48, encoded on three of the four different plasmids (cumulative plasmidome size 604,632 bp). An unusually high number of plasmid-based heavy metal resistance gene (HRG) clusters towards silver, arsenate, cadmium, copper, mercury, and tellurite were also detected. Virulence genes (VGs) for the lipopolysaccharide and capsular polysaccharide structures, iron acquisition (iroBCDEN, ent/fep/fes, sitABCD, iut, and fur), and a type VI secretion system, together with motility genes and Type IV pili, were encoded chromosomally. Thus, a unique combination of chromosomally encoded VGs, together with plasmid-encoded ARGs and HRGs, converged to result in an extreme drug-resistant, pathogenic isolate with survival potential in environmental settings. The use of a disinfectant, octenidine, led to its eradication; however, the existence of a highly antibiotic-resistant isolate with significant virulence potential is a matter of concern in public health settings and warrants further surveillance for extreme drug-resistant Enterobacter isolates.