Clinical and laboratory insights into the threat of hypervirulent Klebsiella pneumoniae.

Hypervirulent Klebsiella pneumoniae (hvKP) typically causes severe invasive infections affecting multiple sites in healthy individuals. In the past, hvKP was characterized by a hypermucoviscosity phenotype, susceptibility to antimicrobial agents, and its tendency to cause invasive infections in healthy individuals within the community. However, there has been an alarming increase in reports of multidrug-resistant hvKP, particularly carbapenem-resistant strains, causing nosocomial infections in critically ill or immunocompromised patients. This presents a significant challenge for clinical treatment. Early identification of hvKP is crucial for timely infection control. Notably, identifying hvKP has become confusing due to its prevalence in nosocomial settings and the limited predictive specificity of the hypermucoviscosity phenotype. Novel virulence predictors for hvKP have been discovered through animal models or machine learning algorithms, while standardization of identification criteria is still necessary. Timely source control and antibiotic therapy have been widely employed for the treatment of hvKP infections. Additionally, phage therapy is a promising alternative approach due to escalating antibiotic resistance. In summary, this narrative review highlights the latest research progress in the development, virulence factors, identification, epidemiology of hvKP, and treatment options available for hvKP infection.

Global phylogeography and genomic characterization of blaKPC and blaNDM-positive clinical Klebsiella aerogenes isolates from China, 2016-2022.

Carbapenem-resistant Klebsiella aerogenes (CRKA), being one of the members of carbapenem-resistant Enterobacteriaceae (CRE), has caused great public health concern, but with fewer studies compared to other CRE members. Furthermore, studies on phylogenetic analysis based on whole genome Single-Nucleotide Polymorphism (SNP) of CRKA were limited. Here, 20 CRKA isolates (11 blaKPC-2-bearing and 9 blaNDM-1/5-harboring) were characterized by antimicrobial susceptibility testing, conjugation assay, whole genome sequencing (WGS) and bioinformatics analysis. Additionally, the phylogeographic relationships of K. aerogenes were further investigated from public databases. All isolates were multidrug-resistant (MDR) bacteria, and they demonstrated susceptibility to colistin. Most blaKPC-2 or blaNDM-1/5-carrying plasmids were found to be conjugative. Phylogenetic analysis revealed the clonal dissemination of K. aerogenes primarily occurred within clinical settings. Notably, some strains in this study showed the potential for clonal transmission, sharing few SNPs between K. aerogenes and KPC- and/or NDM-positive K. aerogenes isolated from various countries. The STs of K. aerogenes strains had significant diversity. WGS analysis showed that the IncFIIK plasmid was the most prevalent carrier of blaKPC-2, and, blaNDM-1/5 were detected on the IncX3 plasmids. The Tn6296 and Tn3000 transposons were most common vehicles for facilitating the transmission of blaKPC-2 and blaNDM-1/5, respectively. This study highlights the importance of continuous screening and surveillance by WGS for analysis of drug-resistant strains in hospital settings, and provide clinical information that supports epidemiological and public health research on human pathogens.

Genomic epidemiology and ceftazidime-avibactam high-level resistance mechanisms of Pseudomonas aeruginosa in China from 2010 to 2022.

Ceftazidime-avibactam (CZA) resistance is a huge threat in the clinic; however, the underlying mechanism responsible for high-level CZA resistance in Pseudomonas aeruginosa (PA) isolates remains unknown. In this study, a total of 5,763 P. aeruginosa isolates were collected from 2010 to 2022 to investigate the ceftazidime-avibactam (CZA) high-level resistance mechanisms of Pseudomonas aeruginosa (PA) isolates in China. Fifty-six PER-producing isolates were identified, including 50 isolates carrying blaPER-1 in PA, and 6 isolates carrying blaPER-4. Of these, 82.1% (46/56) were classified as DTR-PA isolates, and 76.79% (43/56) were resistant to CZA. Importantly, blaPER-1 and blaPER-4 overexpression led to 16-fold and >1024-fold increases in the MICs of CZA, respectively. WGS revealed that the blaPER-1 gene was located in two different transferable IncP-2-type plasmids and chromosomes, whereas blaPER-4 was found only on chromosomes and was carried by a class 1 integron embedded in a Tn6485-like transposon. Overexpression of efflux pumps may be associated with high-level CZA resistance in blaPER-1-positive strains. Kinetic parameter analysis revealed that PER-4 exhibited a similar kcat/Km with ceftazidime and a high (∼3359-fold) IC50 value with avibactam compared to PER-1. Our study found that overexpression of PER-1 combined with enhanced efflux pump expression and the low affinity of PER-4 for avibactam contributes to high-level resistance to CZA. Additionally, the Tn6485-like transposon plays a significant role in disseminating blaPER. Urgent active surveillance is required to prevent the further spread of high-level CZA resistance in DTR-PA isolates.

Characterization of a novel Tn6485h transposon carrying both blaIMP-45 and blaAFM-1 integrated into the IncP-2 plasmid in a carbapenem-resistant Pseudomonas aeruginosa.

OBJECTIVES: To characterize a carbapenem-resistant Pseudomonas aeruginosa (CRPA) with an IncP-2 plasmid containing a novel transposon, Tn6485h, which carries both blaIMP-45 and blaAFM-1. METHODS: Antimicrobial susceptibility testing and filter mating experiment were performed on PA942. The stability of the plasmid carrying both blaIMP-45 and blaAFM-1 was carried out. We determined the growth rate of the transconjugant to investigate fitness cost. Additionally, whole-genome sequencing and genomic analysis were performed on PA942. RESULTS: PA942 strain was resistant to most antibiotics except for ciprofloxacin and colistin. Bioinformatics analysis confirmed that PA942 contains an IncP-2 plasmid with a novel transposon Tn6485h carrying both blaIMP-45 and blaAFM-1. The plasmid pPA942-IMP45 can be transferred into recipient bacteria PAO1Rif with an efficiency of 2.2 × 10-7 and the transconjugant PAO1Rif/ pPA942-IMP45 can be stably inherited for 10 generations in the absence of antibiotics. CONCLUSION: We report a carbapenem-resistant P. aeruginosa strain with an IncP-2 plasmid containing a novel transposon, Tn6485h, which carries both blaIMP-45 and blaAFM-1. The IncP-2 plasmid and transposon Tn6485h may contribute to the spread of MBL genes. Therefore, effective measures to prevent the spread of these plasmids should be taken.

Transcriptomic landscape of GC-2spd(ts) cell in response to the downregulation of piR-1207/2107.

Spermatogenesis is a highly orchestrated dynamic developmental process, during which piRNAs play an indispensable role. Our previous studies have confirmed that the levels of piR-1207 and piR-2107 were significantly decreased in spermatozoa and seminal plasma of patients with asthenozoospermia, compared with the fertile controls. In order to explore the function of piR-1207 and piR-2107 in human spermatogenesis and their potential regulatory downstream genes, we examined the transcriptomic landscape in mouse spermatocyte cell line GC-2spd(ts) transfected with anti-piR-1207 and anti-piR-2107 by RNA sequencing. The result showed that 86 and 75 differential expression genes (DEGs) in anti-piR-1207 and anti-piR-2107 group, respectively. Among the DEGs, three genes including Pbp2, Pde3a and Cage1 were identified as potential key genes playing important roles in mediating sperm motility and morphology in anti-piR-1207 or anti-piR-2107 transfected transcriptomic response. Next, the expression levels of Pbp2, Pde3a and Cage1 were confirmed by qRT-PCR. These results showed that Pbp2, Pde3a and Cage1 may serve as the potential regulatory genes of piR-1207 or piR-2107. In summary, piR-1207 and piR-2107 might have an implication in modulating the process of spermatogenesis through regulating the expression of potential genes.

Deuterated Ethanol as a Probe for Measuring Equilibrium Isotope Effects for Hydroxyl Exchange.

Equilibrium deuterium isotope effects for exchange of hydroxyl deuterons and protons among tert-butanol, phenol, ethanethiol, diethylamine, and ethanol were measured by using NMR and also calculated theoretically. Deuterated ethanol could be used as a probe for measuring equilibrium isotope effects (EIE) for hydroxyl exchange; tert-butanol, phenol, ethanethiol, diethylamine, and pyrrole were used as five representive examples. A procedure called the "one-atom isotope effect" was used to save time in the calculations.

Carving two adjacent holes on [60]fullerene through two consecutive epoxide to diol to dione transformations.

Repeated acid catalyzed epoxide opening and oxidation of the resulting diol with diacetoxyiodobenzene led to two 10-membered orifices on C(60) cage.

Synthesis of fullerene oxides containing both 6,6-closed epoxide and 5,6-open ether moieties through thermolysis of fullerene peroxides.

Thermolysis of the fullerene hexaadduct C(60)(OO(t)Bu)(6) results in cleavage of two O-O bonds and elimination of two tert-butoxy groups to form two isomeric products with the formula C(60)(O)(2)(OO(t)Bu)(4) in comparable yields. The two oxygen atoms exist as two epoxy groups in one isomer 3, and as an epoxy and an ether group in the other isomer 2. Addition of hydroxylamine to 2 opens both the epoxy and the ether moieties to give a cage-opened keto-ketoxime derivative.

Switched role of fullerene in the Diels-Alder reaction: facile addition of dienophiles to the conjugated fullerene diene moiety.

The isolated cyclopentadiene moiety in a fullerene multi-adduct derivative reacts readily with dienophiles to form [4 + 2] cycloaddition products.

Towards the rational synthesis of norfullerenes. controlled deletion of one carbon atom from C60 and preparation of 2,5,9-trioxo-1-nor(C60-Ih)[5,6]fullerene C59(O)3 derivatives.

Norfullerenes are fullerene-like compounds (fulleroids) resulting from partial deletion of fullerene skeleton carbons. The one carbon less norfullerene C59(O) 3 derivatives having three carbonyl groups on the rim of the orifice are prepared through peroxide-mediated reactions. A key step involves a novel PCl 5 initiated rearrangement of a hydroxyl amine adduct. Decarboxylation serves as the carbon removal step.

Synthesis of [59]fullerenones through peroxide-mediated stepwise cleavage of fullerene skeleton bonds and X-ray structures of their water-encapsulated open-cage complexes.

Fullerene skeleton modification has been investigated through selective cleavage of the fullerene carbon-carbon bonds under mild conditions. Several cage-opened fullerene derivatives including three [59]fullerenones with an 18-membered-ring orifice and one [59]fullerenone with a 19-membered-ring orifice have been prepared starting from the fullerene mixed peroxide 1, C60(OOtBu)6. The prepositioned tert-butyl peroxy groups in 1 serve as excellent oxygen sources for formation of hydroxyl and carbonyl groups. The cage-opening reactions were initiated by photoinduced homolysis of the tBu-O bond, followed by sequential ring expansion steps. A key step of the ring expansion reactions is the oxidation of adjacent fullerene hydroxyl and amino groups by diacetoxyliodobenzene (DIB). Aminolysis of a cage-opened fullerene derivative containing an anhydride moiety resulted in multiple bond cleavage in one step. A domino mechanism was proposed for this reaction. Decarboxylation led to elimination of one carbon atom from the C60 cage and formation of [59]fullerenones. The cage-opened [59]fullerenones were found to encapsulate water under mild conditions. All compounds were characterized by spectroscopic data. Single-crystal structures were also obtained for five skeleton-modified derivatives including two water-encapsulated fulleroids.