Redundant carbapenemase-producing (RCP) bacteria, which carry double or multiple carbapenemases, represent a new and concerning phenomenon. The objective of this study is to conduct a comprehensive analysis of the epidemiology and genetic mechanisms of RCP strains to support targeted surveillance and control measures. A retrospective analysis was conducted using surveillance data from 277 articles. Statistical analysis was performed to determine and evaluate species prevalence, proportions of carbapenemases, antibiotic susceptibility profiles, sample information, and patient outcomes. Complete plasmid sequencing data were utilized to investigate potential antimicrobial resistance or virulence advantages that strains may gain from acquiring redundant carbapenemases. RCP bacteria are widely distributed globally, and their prevalence is increasing over time. Several countries, including China, India, Iran, Turkey, and South Korea, have reported more than 100 RCP strains. The most commonly reported RCP species are
Legionella pneumophila, an environmental bacterium that parasitizes protozoa, causes Legionnaires' disease in humans that is characterized by severe pneumonia. This bacterium adopts a distinct biphasic life cycle consisting of a nonvirulent replicative phase and a virulent transmissive phase in response to different environmental conditions. Hence, the timely and fine-tuned expression of growth and virulence factors in a life cycle-dependent manner is crucial for survival and replication. Here, we report that the completion of the biphasic life cycle and bacterial pathogenesis is greatly dependent on the protein homeostasis regulated by caseinolytic protease P (ClpP)-dependent proteolysis. We characterized the ClpP-dependent dynamic profiles of the regulatory and substrate proteins during the biphasic life cycle of L. pneumophila using proteomic approaches and discovered that ClpP-dependent proteolysis specifically and conditionally degraded the substrate proteins, thereby directly playing a regulatory role or indirectly controlling cellular events via the regulatory proteins. We further observed that ClpP-dependent proteolysis is required to monitor the abundance of fatty acid biosynthesis-related protein Lpg0102/Lpg0361/Lpg0362 and SpoT for the normal regulation of L. pneumophila differentiation. We also found that the control of the biphasic life cycle and bacterial virulence is independent. Furthermore, the ClpP-dependent proteolysis of Dot/Icm (defect in organelle trafficking/intracellular multiplication) type IVB secretion system and effector proteins at a specific phase of the life cycle is essential for bacterial pathogenesis. Therefore, our findings provide novel insights on ClpP-dependent proteolysis, which spans a broad physiological spectrum involving key metabolic pathways that regulate the transition of the biphasic life cycle and bacterial virulence of L. pneumophila, facilitating adaptation to aquatic and intracellular niches.
Laribacter hongkongensis is a new emerging foodborne pathogen that causes community-acquired gastroenteritis and traveler's diarrhea. However, the genetic features of L. hongkongensis have not yet been properly understood. A total of 45 aquatic animal-associated L. hongkongensis strains isolated from intestinal specimens of frogs and grass carps were subjected to whole-genome sequencing (WGS), along with the genome data of 4 reported human clinical strains, the analysis of virulence genes, carbohydrate-active enzymes, and antimicrobial resistance (AMR) determinants were carried out for comprehensively understanding of this new foodborne pathogen. Human clinical strains were genetically more related to some strains from frogs inferred from phylogenetic trees. The distribution of virulence genes and carbohydrate-active enzymes exhibited different patterns among strains of different sources, reflecting their adaption to different host environments and indicating different potentials to infect humans. Thirty-two AMR genes were detected, susceptibility to 18 clinical used antibiotics including aminoglycoside, chloramphenicol, trimethoprim, and sulfa was checked to evaluate the availability of clinical medicines. Resistance to Rifampicin, Cefazolin, ceftazidime, Ampicillin, and ceftriaxone is prevalent in most strains, resistance to tetracycline, trimethoprim-sulfamethoxazole, ciprofloxacin, and levofloxacin are aggregated in nearly half of frog-derived strains, suggesting that drug resistance of frog-derived strains is more serious, and clinical treatment for L. hongkongensis infection should be more cautious.
Abstract Nitrogen is important for fungal growth and development, and the GATA transcription factor AreA has been widely studied as a key regulator of nitrogen catabolite repression (NCR) in many fungi. However, AreB, another GATA transcription factor in the NCR pathway, remains less studied, and its role in Aspergillus flavus is still unclear. In this study, we characterized areB in A. flavus and investigated its role in regulating nitrogen utilization, fungal growth, and aflatoxin production. The areB gene produces three transcripts, with areB-α being the most abundantly expressed, particularly under nitrogen-limited conditions. Gene expression analysis via qPCR confirmed that areB acts as a negative regulator of NCR, as its deletion led to the upregulation of NCR-related genes under nitrogen-limiting conditions. Gene function analysis of areB revealed that its deletion impaired hyphal growth, reduced conidia production, and delayed conidial germination. Additionally, deletion of areB led to increased aflatoxin production, particularly under less favorable nitrogen sources, while overexpression of areB reduced aflatoxin levels. Furthermore, areB influenced sclerotia formation in a nitrogen-source-dependent manner. These findings reveal the multifaceted role of areB in nitrogen regulation, fungal development, and secondary metabolism, offering insights for controlling aflatoxin contamination and fungal growth.
AbstractBackground: Klebsiella oxytoca has become an important pathogen for opportunistic infections. Plasmid-mediated multidrug-resistant strains pose a significant risk to public health, especially when the strains produce carbapenemase. Here, we report the first detection of a blaKPC-2-IncFII plasmid and a blaVEB-3-IncC plasmid in a clinical multidrug-resistant K. oxytoca strain YL6, which has an entire cluster regularly spaced short palindromic repeat (CRISPR)-Cas immune system. Case presentation and methods: A 46-year-old man was hospitalized with chronic fibrous pneumonia. The K. oxytoca strain YL6 was isolated from his sputum sample. It was resistant to all tested antimicrobials, including almost all β-lactams, cephalosporins, quinolones, and aminoglycosides, except for colistin and tigecycline. To investigate this strain further, we conducted whole-genome sequencing and sequence alignment. Furthermore, the emerging plasmids were compared with similar ones available in the gene bank better to understand the genetic composition and evolution of the plasmids. Results: K. oxytoca strain YL6 belongs to ST27. This stain possesses a chromosome with 6,111,288 bp and two plasmids (An IncFII plasmid pYL6-1 and An IncC plasmid pYL6-2) with 101,530 bp and 145,051 bp, respectively. Genomic comparative analysis revealed that pYL-1 shared 70%~85% query cover and 98.65%-99.85% nucleotide identity with nineteen similar IncFII plasmids, and pYL-2 shared 79%~93% query cover and 99.74%-99.99% nucleotide identity with twenty-one similar IncC plasmids. Both groups of plasmids retained the complete coding region of the tra gene during their evolution. We also observed that the blaKPC-2 gene was located on an ISKpn19-orf1-orf2-Tn3-ISKpn27-blaKPC-2-ISKpn6-orf2-orf1-ISKpn19 structure in the multidrug resistance (MDR) region of pYL-1. Meanwhile, the blaVEB-3 gene in pYL6-2 was situated in an IS26-IS6100-blaVEB-3-transpone-ISAs1-qacEΔ1-sul1-ISCR1 casset. Based on additional data, the YL6 strain appears to possess an intact type I-E CRISPR -Cas immune system, which had been confirmed to inhibit the invasion and existence of the blaKPC-IncF plasmid effectively. The proto-spacers gene in pYL6-1, which are essential for the function of the CRISPR-Cas immune system, was no match to the CRISPR system sequence of K. oxytoca. Conclusions: We first reported a multidrug-resistant K. oxytoca with an intact CRISPR-Cas immune system harbors a blaVEB-3-IncC plasmid and a blaKPC-2-IncFII plasmid. There are no proto-spacer sequences matching the CRISPR system of K. oxytoca on the IncFII plasmid pYL6-1, which is crucial for identifying the foreign gene. It is inferred that the blaKPC-2-IncFII plasmid might escape the host's immune recognition by avoiding its proto-spacer DNA Base sequences complementing the gene arrangements of the strain's CRISPR system. The mutual adaptation between the invasive plasmid and host bacteria is bound to increase bacterial drug resistance further and lead to an antimicrobial public crisis, which calls for considerable attention.
Abstract The full text of this preprint has been withdrawn by the authors due to author disagreement with the posting of the preprint. Therefore, the authors do not wish this work to be cited as a reference. Questions should be directed to the corresponding author.
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