Insect female reproduction which comprises the synthesis of vitellogenein (Vg) in the fat body and its incorporation into developing oocytes, needs a large amount of energy and food resources. Our previous studies found that juvenile hormone (JH) regulates vitellogenesis in the brown planthopper, Nilaparvata lugens. Here, we report on the role of JH in nutrient-regulated Vg synthesis and egg development. We first cloned the genes coding for juvenile hormone acid methyltransferase (JHAMT) which is involved in JH biosynthesis and methoprene-tolerant (Met) for JH action. Amino acids (AAs) induced the expression of jmtN, while showing no effects on the expression of met using an artificial diet culture system. Reduction in JH biosynthesis or its action by RNA interference (RNAi)-mediated silencing of jmtN or met led to a severe inhibition of AAs-induced Vg synthesis and oocyte maturation, together with lower fecundity. Furthermore, exogenous application of JH III partially restored Vg expression levels in jmtN RNAi females. However, JH III application did not rescue Vg synthesis in these met RNAi insects. Our results show that AAs induce Vg synthesis in the fat body and egg development in concert with JH biosynthesis in Nilaparvata lugens (Stål), rather than through JH action.

The spread of carbapenem-resistant Klebsiella spp. poses a significant public health threat, partly due to the acquisition of the bla _IMP genes, which encode IMP-type metallo-β-lactamases. These enzymes confer resistance to a broad spectrum of β-lactam antibiotics, including carbapenems, thereby complicating treatment options. This study aims to provide a comprehensive genomic characterization of bla _IMP -harboring plasmids across different species within the genus Klebsiella , based on the genomic characteristics of the plasmid pT117-2 of Klebsiella variicola strain T117 isolated from clinical settings in China, along with all available bla _IMP -harboring plasmids of Klebsiella spp. fromthe GenBank database until 26 April 2025. Among the 123 bla _IMP -harboring plasmids of Klebsiella spp., nine variants were identified, with bla _IMP-4 (carried by 69 plasmids) and bla _IMP-1 (carried by 37 plasmids) being the most prevalent. The bla _IMP-4 gene was associated with IncN type (~50 kb, conjugative) and untypeable (~300 kb, non-mobilizable) plasmids in China, whereas in Australia, it was linked to IncC (~200 kb) and IncM2 (~80 kb) type conjugative plasmids. Meanwhile, bla _IMP-1 was found to be associated with IncN (~50 kb), IncM (~80 kb), and IncFII (80 ~200 kb) type conjugative plasmids mainly in Japan. Notably, our results highlight the prevalence of IncN-type conjugative plasmids, including the plasmid pT117-2 identified in this study, as key vehicles for the dissemination of bla _IMP genes. This study provides critical insights into the genetic mechanisms of bla _IMP -harboring plasmids persistence and spread in Klebsiella spp., advancing our understanding of their dissemination. IMPORTANCE: Carbapenem-resistant Enterobacterales (CRE) mediated by metallo-β-lactamases (MBLs) pose a major global public health threat that challenges clinical antimicrobial therapy; based on our study, bla _IMP-4 in China is predominantly associated with IncN plasmids (forming the “IncN- bla _IMP-4 - qnrS1 ” axis), while bla _IMP-1 in Japan links to IncN/IncM/IncFII plasmids, with these regional differences highlighting the need for geographically targeted surveillance, and notably, the high-risk ST146 Klebsiella variicola carrying bla _IMP-4 on a conjugative IncN plasmid serves as an underrecognized reservoir for resistance genes, extending surveillance beyond common pathogenic Enterobacterales ; limitations of this study include restricted sample size and geographic scope, and future research should validate these patterns via multi-center studies, explore plasmid evolution mechanisms, and integrate findings into routine surveillance to optimize antibiotic stewardship and infection control, thereby mitigating the global spread of MBL-mediated CRE.

The global spread of carbapenem-resistant Pseudomonas aeruginosa (CRPA) poses a critical clinical threat, with bla _KPC as a key mobile carbapenem resistance gene. Here, we investigated a novel bla _KPC-2 genetic element and its transmission in clinical ST2483 isolate PA100 via whole-genome sequencing, molecular, and phenotypic testing, and vesicle analysis. A unique 4,746-bp IS 26 -flanked structure inserted at the chromosomal InaA/pncB2 locus was confirmed, which forms a circular transposition intermediate through IS 26 recombination. PA100 exhibited ~40-fold higher bla _KPC-2 copy number and ~25-fold higher mRNA expression vs chromosomal bla _KPC-2 strain PA3; meropenem exposure further elevated its transcription by nearly 70-fold, far exceeding controls. PA100 showed an extensively drug-resistant phenotype with high-level carbapenem resistance, while remaining susceptible to ceftazidime-avibactam and cefiderocol. No classical conjugation or transformation was observed, while intact outer membrane vesicles (OMVs) from PA100 carried bla _KPC-2 , supporting a non-plasmid, vesicle-associated route for transient delivery of the resistance gene under the tested conditions. The circular transposon remained genetically stable after 10 generations of passaging in PA100; however, stable maintenance in the PAO1 recipient was not detected after passage. In summary, we first report an IS 26 -driven circular bla _KPC-2 transposon in ST2483 P. aeruginosa , conferring robust overexpression and stable inheritance in the donor strain, with OMVs potentially facilitating its horizontal spread, although stable maintenance in recipient cells was not demonstrated under the current assay conditions. These data advance understanding of bla _KPC dissemination in CRPA and highlight clinical surveillance priorities for rare high-risk sequence types.

Objectives: KPC-producing Pseudomonas aeruginosa (KPC-PA) has emerged as an important multidrug-resistant pathogen, yet its population structure and lineage-associated genomic variation remain incompletely understood. We investigated the genomic epidemiology of an international collection of KPC-PA genomes to characterize population structure, evolutionary patterns, and lineage-associated genomic features. Methods: A complete genome of a clinical ST463 isolate (PA328) was generated using hybrid sequencing and analyzed together with 655 publicly available KPC-PA genomes. Comparative genomic, phylogenomic, pangenome, recombination, and Bayesian temporal analyses were performed to investigate population structure and identify genomic features associated with major lineages. Results: Among 656 KPC-PA genomes, bla _KPC−2 (99.5%) and ST463 (43.6%) were predominant. Population genomic analysis resolved eight major phylogenetic lineages with distinct sequence-type compositions and geographic distributions, including ST463 in China, ST282 in the United States, and ST654 in Chile. Assembly-based screening identified candidate frameshift calls in genes annotated as being involved in metabolism, iron acquisition, transport, and virulence-associated functions, providing potential targets for further investigation using read-level confirmation. Descriptive analyses revealed lineage-associated patterns of antimicrobial resistance genes (ARGs) and mobile genetic elements co-occurrence. Within ST463, an operationally defined high-recombination region (HRR) contained genes annotated as being related to secretion systems, biofilm formation, metabolism, and mobile genetic elements. Bayesian analysis estimated the time to the most recent common ancestor (tMRCA) of the sampled Chinese ST463 population at approximately 2005. Partial similarity between plasmid sequences and the HRR suggested potential evolutionary connections, although their specific relationship requires further investigation. Conclusions: This study characterizes the population structure and lineage-associated genomic variation of KPC-PA within a large international genome collection. The findings provide a descriptive genomic resource for understanding KPC-PA evolution and surveillance, and highlight candidate genomic features that warrant further structure-aware analyses and experimental investigation.

Proteus mirabilis is an emerging multidrug-resistant (MDR) pathogen capable of causing severe nosocomial infections. This study characterizes a MDR and carbapenem-resistant P. mirabilis strain 20119 isolated from the respiratory tract of a pneumonia inpatient in China. A systematic investigation of antibiotic resistance genes (ARGs) and their genetic environments was conducted. Whole-genome sequencing (WGS) revealed the chromosomal carriage of bla _OXA-23 , a gene encoding a class D carbapenemase, within a Tn 2006 composite transposon flanked by IS Aba1 elements. Global biogeographic analysis of the P. mirabilis strains with a complete genome indicated that Tn 2006 -associated bla _OXA-23 -harboring P. mirabilis strains were predominant in Asia, while Tn 2008 -associated bla _OXA-23 -harboring P. mirabilis strains were prevalent in Europe. In order to clarify the genetic contexts and mechanisms underlying bla _OXA-23 -mediated carbapenem resistance and other ARGs, we categorized the major genetic backdrop associated with chromosomally located ARGs in P. mirabilis strain 20119 into five sections: (i) the carbapenem-resistant region harboring bla _OXA-23 ; (ii) the resistance structure “IS Ecp1-bla _CTX-M-14 -IS 903B/ ∆IS 903B ”; (iii) the MDR region harboring mph(E ), msr(E ), armA , and sul1; (iv) the prophage containing bla _DHA-1 and qnrB4; and (v) the Tn 7 class two integron harboring aadA1 , sat2, and dfrA1 . IMPORTANCE: The dissemination of carbapenem-resistant P. mirabilis poses a severe clinical threat owing to constrained effective therapeutic alternatives. This work is significant, as it provides the first complete genomic identification of a bla _OXA-23 -harboring human-derived P. mirabilis in China and the first worldwide isolate from the respiratory tract with a complete genome. The P. mirabilis strain 20119 exhibited an MDR profile, harboring additional resistance genes ( bla _CTX-M-14 , bla _DHA-1 , armA , etc.) clustered within mobile genetic elements (MGE, e.g., IS Ecp1 , IS 26 , prophage, and class 2 integron), facilitating horizontal transfer. This study focuses on describing the genomic contexts of the five resistance regions co-occurring with bla _OXA-23 and other ARGs. This study underscores the emergence of P. mirabilis as a concerning reservoir for bla _OXA-23 and other ARGs and highlights the fundamental contribution of MGEs to horizontal gene transfer (HGT).