Transcriptomic analysis of nitrogen metabolism pathways in Klebsiella aerogenes under nitrogen-rich conditions.

The acceleration of the nitrogen cycle and the nitrogen excess observed in some coastal waters has increased interest into understanding the biochemical and molecular basis of nitrogen metabolism in various microorganisms. To investigate nitrogen metabolism of a novel heterotrophic nitrification and aerobic denitrification bacterium Klebsiella aerogenes strain (B23) under nitrogen-rich conditions, we conducted physiological and transcriptomic high-throughput sequencing analyses on strain B23 cultured on potassium nitrate-free or potassium nitrate-rich media. Overall, K. aerogenes B23 assimilated 82.47% of the nitrate present into cellular nitrogen. Further, 1,195 differentially expressed genes were observed between K. aerogenes B23 cultured on potassium nitrate-free media and those cultured on potassium nitrate-rich media. Gene annotation and metabolic pathway analysis of the transcriptome were performed using a series of bioinformatics tools, including Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and Non-Redundant Protein Database annotation. Accordingly, the nitrogen metabolism pathway of K. aerogenes B23 was analyzed; overall, 39 genes were determined to be involved in this pathway. Differential expression analysis of the genes involved in the nitrogen metabolism pathway demonstrated that, compared to the control, FNR, NarK/14945, fdx, gshA, proB, proA, gapA, argH, artQ, artJ, artM, ArgR, GAT1, prmB, pyrG, glnS, and Ca1 were significantly upregulated in the nitrogen-treated K. aerogenes B23; these genes have been established to be involved in the regulation of nitrate, arginine, glutamate, and ammonia assimilation. Further, norV, norR, and narI were also upregulated in nitrogen-treated K. aerogenes B23; these genes are involved in the regulation of NO metabolism. These differential expression results are important for understanding the regulation process of key nitrogen metabolism enzyme genes in K. aerogenes B23. Therefore, this study establishes a solid foundation for further research into the expression regulation patterns of nitrogen metabolism-associated genes in K. aerogenes B23 under nitrogen-rich conditions; moreover, this research provides essential insight into how K. aerogenes B23 utilizes nutritional elements.

Genomic Characterization of Escherichia coli Co-Producing KPC-2 and NDM-5 Carbapenemases Isolated from Intensive Care Unit in a Chinese Hospital.

Background: Around the world, carbapenemase-producing Escherichia coli is becoming more prevalent. The purpose of this research was to analyze the whole plasmid sequences from YL03 isolates of the E. coli strain that produce both KPC-2 and NDM-5 carbapenemases. Materials and Methods: Whole-genome sequencing (WGS) and analysis of E. coli strain YL03, which was isolated from a wound sample, was performed by Illumina Novaseq 6000 and Pacific Biosciences Sequel (PacBio, Menlo Park, CA) sequencers. Following that, the WGS results were used to predict and analyze the YL03 genome composition and function. A complete gene sequence for YL03 with the accession number CP093551 has been uploaded to GenBank. Results: The results showed that YL03 co-carried five resistance genes, which included blaKPC-2, blaNDM-5, blaTEM-1B, blaCTX-M-14, and mdf(A). Furthermore, three resistance plasmids were found in YL03: pYL03-KPC, pYL03-NDM, and pYL03-CTX. Among them, the 53 kb-long pYL03-KPC plasmid belonging to the IncP, carried the replicase gene (repA) and the carbapenemase gene (blaKPC-2). The blaKPC-2 gene was flanked by a composite transposon-like element (Tn3-[Tn3] tnpR-ISKpn27 blaKPC--ISKpn6). Conclusions: The YL03 strain co-carried blaKPC-2 and blaNDM-5 and had a unique multidrug resistance plasmid containing blaKPC-2.

Characterization of Resistance and Virulence of Pasteurella multocida Isolated from Pet Cats in South China.

Pasteurella multocida, one of the major zoonotic pathogens, may cause localized cellulitis, bacteremia, septic shock, and other symptoms in people. Accidental bites or scratches in close contact between humans and cats are one of the causes of P. multocida infection in humans. The prevalence of diseases due to P. multocida in humans may be rising as a result of the popularity of cat cafes in China. However, the epidemiology of P. multocida in cat-themed cafes in South China is yet to be reported. P. multocida in 92 healthy cats from four cafes with pet-cat themes was examined in their tonsils and oral cavities. The antibiotic susceptibility of each isolate was evaluated by using the disk-susceptibility testing method. The 19 P. multocida were selected for whole-genome sequencing (WGS), together with the genome data of eight previously described clinical strains isolated from humans, and the analysis of antimicrobial resistance (AMR) determinants, capsular genotyping, MLST genotyping, and virulence gene profiles was carried out. The results showed that 48.91% of cats (45/90) were positive for P. multocida. All isolated P. multocida stains were highly resistant to erythromycin (15 µg) (100%) and nonsensitive to fluoroquinolones (5 µg) (37.38%), while they were all susceptible to penicillin (10 untis), tetracycline (30 µg), doxycycline (30 µg), and chloramphenicol (30 µg). According to WGS analysis, those with the gyrA resistance gene were all insensitive to fluoroquinolone antibiotics. Virulence gene profiles showed that the genes pfhA, nanH, and plpB were practically all present in cats compared to humans. To conclude, increased antibiotic resistance, along with virulence factors, complicates the treatment of P. multocida infection. Thus, clinical treatment for P. multocida infection should be performed more cautiously.

Evaluation of 3D-printed oval root canal preparation by small field-of-view cone beam CT and computer-aided technique / 口腔疾病防治

Objective@# To evaluate the effect of 3D-printed oval root canal preparation by using small field-of-view cone beam CT (CBCT) combined with computer-aided technologies.@*Methods@#An extracted tooth with a suitable single oval canal was selected by small field-of-view CBCT scanning. Three-dimensional (3D)-printed resin teeth were obtained based on the CBCT data after data conversion and processing. 50 general dentists were selected to prepare the oval root canal of the resin teeth with X-Gold rotary Ni-Ti instruments. Small field-of-view CBCT was applied to scan the oval root canals before and after preparation. Then, computer-aided technologies were used to calculate and compare these CBCT data, analyzing the effects of oval root canal cleaning as well as the root canal deviation by 3D reconstruction and rendering of the images.@*Results @#Among the 50 cases, the mean unprepared area of the oval root canal wall was（56.20 ± 11.91）% and the mean maximum deviation distance of the root canal was（0.140 ± 0.041）mm. There was no correlation between root canal cleanliness and deviation (r=0.18, P=0.212).@*Conclusion @# Combined with small field-of-view CBCT and computer-aided technology, we can effectively quantitatively evaluate the root canal preparation effect.