Emergence of plasmid-borne tet(X4) resistance gene in clinical isolate of eravacycline- and omadacycline-resistant Klebsiella pneumoniae ST485.

Omadacycline and eravacycline are gradually being used as new tetracycline antibiotics for the clinical treatment of Gram-negative pathogens. Affected by various tetracycline-inactivating enzymes, there have been reports of resistance to eravacycline and omadacycline in recent years. We isolated a strain carrying the mobile tigecycline resistance gene tet(X4) from the feces of a patient in Zhejiang Province, China. The strain belongs to the rare ST485 sequence type. The isolate was identified as Klebsiella pneumoniae by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The MICs of antimicrobial agents were determined using either the agar dilution method or the micro broth dilution method. The result showed that the isolate was resistant to eravacycline (MIC = 32 mg/L), omadacycline (MIC > 64 mg/L), and tigecycline (MIC > 32 mg/L). Whole-genome sequencing revealed that the tet(X4) resistance gene is located on the IncFII(pCRY) conjugative plasmid. tet(X4) is flanked by ISVsa3, and we hypothesize that this association contributes to the spread of the resistance gene. Plasmids were analyzed by S1-nuclease pulsed-field gel electrophoresis (S1-PFGE), Southern blotting, and electrotransformation experiment. We successfully transferred the plasmid carrying tet(X4) to the recipient bacteria by electrotransformation experiment. Compared with the DH-5α, the MICs of the transformant L3995-DH5α were increased by eight-fold for eravacycline and two-fold higher for omadacycline. Overall, the emergence of plasmid-borne tet(X4) resistance gene in a clinical isolate of K. pneumoniae ST485 underscores the essential requirement for the ongoing monitoring of tet(X4) to prevent and control its further dissemination in China.IMPORTANCEThere are still limited reports on Klebsiella pneumoniae strains harboring tetracycline-resistant genes in China, and K. pneumoniae L3995hy adds a new example to those positive for the tet(X4) gene. Importantly, our study raises concerns that plasmid-mediated resistance to omadacycline and eravacycline may spread further to a variety of ecological and clinical pathogens, limiting the choice of medication for extensively drug-resistant bacterial infections. Therefore, it is important to continue to monitor the prevalence and spread of tet(X4) and other tetracyclines resistance genes in K. pneumoniae and diverse bacterial populations.

Distribution and molecular characterization of carbapenemase-producing gram-negative bacteria in Henan, China.

This study aimed to investigate the epidemiological characteristics and trends over time of carbapenemase-producing (e.g., KPC, NDM, VIM, IMP, and OXA-48) Gram-negative bacteria (CPGNB). Non-duplicated multi-drug resistant Gram-negative bacteria (MDRGNB) were collected from the First Affiliated Hospital of Zhengzhou University from April 2019 to February 2023. Species identification of each isolate was performed using the Vitek2 system and confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry according to the manufacturer's instructions. PCR detected carbapenem resistance genes in the strains, strains carrying carbapenem resistance genes were categorized as CPGNB strains after validation by carbapenem inactivation assay. A total of 5705 non-repetitive MDRGNB isolates belonging to 78 different species were collected during the study period, of which 1918 CPGNB were validated, with the respiratory tract being the primary source of specimens. Epidemiologic statistics showed a significant predominance of ICU-sourced strains compared to other departments. Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa were the significant CPGNB in Henan, and KPC and NDM were the predominant carbapenemases. Carbapenem-resistant infections in Henan Province showed an overall increasing trend, and the carriage of carbapenemase genes by CPGNB has become increasingly prevalent and complicated. The growing prevalence of CPGNB in the post-pandemic era poses a significant challenge to public safety.

Development and validation of an ultra-performance liquid chromatography tandem mass spectrometry for target determination of bioactive compounds in Dendrobium spp.

As a medicine-food homology herb, Dendrobium spp. has versatile applications in modern medicine and food industry. Herein, an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) based method was established for simultaneous quantification of six active components, including gigantol, erianin, naringenin, quercetin, rutin, and p-coumaric acid in Dendrobium spp., on the basis of optimized sample preparation, mass spectrometry conditions, and chromatography conditions. Sample extraction was carried out using methanol at a temperature of 60 °C, followed by separation on a T3 C18 column utilizing a gradient eluting program. The results demonstrated excellent linearity (r > 0.999) for the six active components within a specified concentration range. The average recovery rates ranged from 84.7 % to 106.9 %, and the precision (RSD) was within 7.4 %. The detection and quantification limits of this method ranged from 0.34 to 4.17 ng mL-1 and 1.12-13.91 ng mL-1, respectively. The established method demonstrates high accuracy and reliability and is applicable in practical sample detection. Different Dendrobium spp. exhibit specific variations in compound composition, with D. fimbriatum Hook. having a higher content of benzyl compounds and D. crystallinum. Rchb. f. having a higher content of flavonoids. This study provides experimental evidence for the quality and safety regulation of Dendrobium spp.

Destabilization of fear memory by Rac1-driven engram-microglia communication in hippocampus.

Rac1 is a key regulator of the cytoskeleton and neuronal plasticity, and is known to play a critical role in psychological and cognitive brain disorders. To elucidate the engram specific Rac1 signaling in fear memory, a doxycycline (Dox)-dependent robust activity marking (RAM) system was used to label dorsal dentate gyrus (DG) engram cells in mice during contextual fear conditioning. Rac1 mRNA and protein levels in DG engram cells were peaked at 24 h (day 1) after fear conditioning and were more abundant in the fear engram cells than in the non-engram cells. Optogenetic activation of Rac1 in a temporal manner in DG engram cells before memory retrieval decreased the freezing level in the fear context. Optogenetic activation of Rac1 increased autophagy protein 7 (ATG7) expression in the DG engram cells and activated DG microglia. Microglia-specific transcriptomics and fluorescence in situ hybridization revealed that overexpression of ATG7 in the fear engram cells upregulated the mRNA of Toll-like receptor TLR2/4 in DG microglia. Knockdown of microglial TLR2/4 rescued fear memory destabilization induced by ATG7 overexpression or Rac1 activation in DG engram cells. These results indicate that Rac1-driven communications between engram cells and microglia contributes to contextual fear memory destabilization, and is mediated by ATG7 and TLR2/4, and suggest a novel mechanistic framework for the cytoskeletal regulator in fear memory interference.

Difference analysis and characteristics of incompatibility group plasmid replicons in gram-negative bacteria with different antimicrobial phenotypes in Henan, China.

BACKGROUND: Multi-drug-resistant organisms (MDROs) in gram-negative bacteria have caused a global epidemic, especially the bacterial resistance to carbapenem agents. Plasmid is the common vehicle for carrying antimicrobial resistance genes (ARGs), and the transmission of plasmids is also one of the important reasons for the emergence of MDROs. Different incompatibility group plasmid replicons are highly correlated with the acquisition, dissemination, and evolution of resistance genes. Based on this, the study aims to identify relevant characteristics of various plasmids and provide a theoretical foundation for clinical anti-infection treatment. METHODS: 330 gram-negative strains with different antimicrobial phenotypes from a tertiary hospital in Henan Province were included in this study to clarify the difference in incompatibility group plasmid replicons. Additionally, we combined the information from the PLSDB database to elaborate on the potential association between different plasmid replicons and ARGs. The VITEK mass spectrometer was used for species identification, and the VITEK-compact 2 automatic microbial system was used for the antimicrobial susceptibility test (AST). PCR-based replicon typing (PBRT) detected the plasmid profiles, and thirty-three different plasmid replicons were determined. All the carbapenem-resistant organisms (CROs) were tested for the carbapenemase genes. RESULTS: 21 plasmid replicon types were detected in this experiment, with the highest prevalence of IncFII, IncFIB, IncR, and IncFIA. Notably, the detection rate of IncX3 plasmids in CROs is higher, which is different in strains with other antimicrobial phenotypes. The number of plasmid replicons they carried increased with the strain resistance increase. Enterobacterales took a higher number of plasmid replicons than other gram-negative bacteria. The same strain tends to have more than one plasmid replicon type. IncF-type plasmids tend to be associated with MDROs. Combined with PLSDB database analysis, IncFII and IncX3 are critical platforms for taking blaKPC-2 and blaNDM. CONCLUSIONS: MDROs tend to carry more complex plasmid replicons compared with non-MDROs. The plasmid replicons that are predominantly prevalent and associated with ARGs differ in various species. The wide distribution of IncF-type plasmids and their close association with MDROs should deserve our attention. Further investigation into the critical role of plasmids in the carriage, evolution, and transmission of ARGs is needed.

The reduced mortality of malignant melanoma at the population level is mainly attributable to treatment advances for the past decade.

BACKGROUND: Cutaneous malignant melanoma (CMM) causes most skin cancer deaths in the United States (US). The mortality has been decreasing in the US population. We hypothesize that this population-level reduction is mainly attributable to the treatment advances, rather than the successful primary and secondary prevention. METHODS: Using data from the Surveillance, Epidemiology, and End Results (SEER) databases, we collected the incidence, incidence-based mortality (IBM), and 5-year survival (5-YS) rates of CMM from 1994 to 2019. Trends by stage and sex were examined by joinpoint regression analyses and age-period-cohort analyses. RESULTS: The overall incidence of CMM rose by 1.6% yearly from 1994 to 2006 (95% confidence interval [CI]: 0.9% to 2.2%) and then increased with a numerical trend. And we projected the incidence will continue to increase until 2029. In contrast, the IBM for all CMM has decreased yearly by 2.8% (95% CI: -3.9% to -1.8%) since 2010 after continuously increasing by 3.8% annually (95% CI: 3.2% to 4.4%) from 1996 to 2010. For early-stage (localized and regional) CMM, we found the incidence since 2005 plateaued without further increase, while the incidence for CMM at distant stage continuously increased by 1.4% per year (95% CI: 0.9% to 2.0%). Improvements in 5-YS were observed over the study period for all CMM and were most obvious in distant stage. And significant period effects were noted around the year 2010. CONCLUSION: This study demonstrated improved survival and reduced mortality of CMM at the US population level since 2010, which were consistent with the introduction of novel therapies. Encouraging effects of primary prevention among adolescents in the most recent cohorts were found. However, the plateaued overall incidence and early diagnosis rates indicated that advances in primary and secondary prevention are very much needed to further control the burden of CMM.