Genetic characterisation of antibiotic resistance transposons Tn6608 and Tn6609 isolated from clinical Pseudomonas strains in Cyprus

Isolation, identification and the pathogenicity characterization of Pseudomonas putida 1C3 and its activation on immune responses in Japanese flounder (Paralichthys olivaceus)

The outbreak of mass mortality of Japanese flounder occurred in an aquaculture farm in Hebei province of China. This study isolated and identified Pseudomonas putida as the dominant bacterium from diseased Japanese flounder (Paralichthys olivaceus) based on morphological, physiological, biochemical characteristics, 16S rRNA gene sequencing, and whole-genome sequencing. Pathogenicity assessment, histopathological analysis, and host immune response were investigated. Results demonstrated that P. putida was pathogenic, causing acute enteritis and multiple organ damage in infected fish. The median lethal dose (LD50) was determined as 2.66 × 106 CFU/g. Transcriptome analysis of the spleen at three post-infection timepoints revealed a robust immune response, with significantly upregulation of immune pathways and downregulation of metabolic functions. Key cytokines (il-1β, il-6, tnf, il-8, il-12, cxcl10, ccl2) were significantly upregulated, indicating intense immune activation. Notably, the P. putida strain exhibited a multidrug-resistant phenotype and harbored multiple drug resistance genes and virulence factors. This is the first report linking P. putida to disease in P. olivaceus, comprehensively elucidating its causative role and the host immune response in Japanese flounder culture.

Molecular characterization of virulent genes in Pseudomonas aeruginosa based on componential usage divergence

Genetic characteristics of virulent genes in Pseudomonas aeruginosa attracted significant attention for they could govern their drug-resistances. Studies on the componential usage divergences in the virulent genes are beneficial for further explicating their molecular characteristics. In present study, one thousand complete genomes of Pseudomonas aeruginosa were considered to study the molecular characteristics of 21 typical virulent genes. The important componential usage patterns (i.e., the base usage pattern, the codon usage pattern and their divergences) of 21 specific virulent genes were counted and calculated. The results show that (1) most virulent genes concerned in the present study are high GC sequences (overall GC ratio > 50%), especially from the codon usage perspective, the virulent genes are obviously GC3-abundant sequences (GC3 ratio > 70%); (2) the relative synonymous codon usage of all concerned virulent genes are uneven, especially in the anvM and the lptA, there is no codon for some certain amino acids, which could reveal their obvious codon usage bias; (3) some genes (i.e., the oprF and the fadD1) with lower divergence have steady effective number of codons. The findings of the present work would improve novel insights on the genetic characteristics of virulent genes in Pseudomonas aeruginosa.

Prioritization of Critical Factors for Surveillance of the Dissemination of Antibiotic Resistance in Pseudomonas aeruginosa: A Systematic Review

Pseudomonas aeruginosa is the primary opportunistic human pathogen responsible for a range of acute and chronic infections; it poses a significant threat to immunocompromised patients and is the leading cause of morbidity and mortality for nosocomial infections. Its high resistance to a diverse array of antimicrobial agents presents an urgent health concern. Among the mechanisms contributing to resistance in P. aeruginosa, the horizontal acquisition of antibiotic resistance genes (ARGs) via mobile genetic elements (MGEs) has gained recognition as a substantial concern in clinical settings, thus indicating that a comprehensive understanding of ARG dissemination within the species is strongly required for surveillance. Here, two approaches, including a systematic literature analysis and a genome database survey, were employed to gain insights into ARG dissemination. The genome database enabled scrutinizing of all the available sequence information and various attributes of P. aeruginosa isolates, thus providing an extensive understanding of ARG dissemination within the species. By integrating both approaches, with a primary focus on the genome database survey, mobile ARGs that were linked or correlated with MGEs, important sequence types (STs) carrying diverse ARGs, and MGEs responsible for ARG dissemination were identified as critical factors requiring strict surveillance. Although human isolates play a primary role in dissemination, the importance of animal and environmental isolates has also been suggested. In this study, 25 critical mobile ARGs, 45 critical STs, and associated MGEs involved in ARG dissemination within the species, are suggested as critical factors. Surveillance and management of these prioritized factors across the One Health sectors are essential to mitigate the emergence of multidrug-resistant (MDR) and extensively resistant (XDR) P. aeruginosa in clinical settings.

First Identification of a Multidrug-Resistant Pseudomonas putida Co-Carrying Five β-Lactam Resistance Genes Recovered from a Urinary Tract Infection in China

The emergence of multidrug-resistant Pseudomonas spp. in the clinical settings has heightened public awareness. Here, we described the genomic characteristics of a P. putida isolate co-carrying five β-lactam resistance genes recovered from a urinary tract infection in China. Whole-genome sequencing was performed using Illumina NovaSeq 6000 and Oxford Nanopore MinION platforms. The genome sequence was annotated and further subjected to identify the sequence type (ST), antibiotic resistance and virulence genes. Phylogenetic analysis of 193 P. putida strains stored in NCBI public database based on core genome single nucleotide polymorphism (cgSNP) strategy were also performed and visualized. Our study indicated that P. putida PP_2463 was resistant to a wide range of antimicrobial agents tested, including aminoglycosides, carbapenems and fluoroquinolones. The complete genome sequence of P. putida PP_2463 is made up of one chromosome and two plasmids, which could be assigned to a new sequence type (ST) 148. The co-occurrence of β-lactam resistance genes bla_IPM-15, bla_PME-1, bla_CARB-2, and bla_NDM-1 were first identified in P. putida, and a novel β-lactamase gene located in the chromosome were among the antimicrobial resistance genes discovered. The closest relative of P. putida PP_2463 was identified in 2012 from a urine sample in China, with a difference of 143 SNPs. Along with the presence of multiple β-lactamase genes and mobile genetic elements, the multidrug-resistant phenotype suggests a significant potential as an antibiotic resistance reservoir for Pseudomonas spp.