The role of Type III secretion system in the pathogenesis of Pseudomonas aeruginosa microbial keratitis

Selection of vaccine candidates against Pseudomonas koreensis using reverse vaccinology and a preliminary efficacy trial in Empurau (Tor tambroides)

This study marks the first utilization of reverse vaccinology to develop recombinant subunit vaccines against Pseudomonas koreensis infection in Empurau (Tor tambroides). The proteome (5538 proteins) was screened against various filters to prioritize proteins based on features that are associated with virulence, subcellular localization, transmembrane helical structure, antigenicity, essentiality, non-homology with the host proteome, molecular weight, and stability, which led to the identification of eight potential vaccine candidates. These potential vaccine candidates were cloned and expressed, with six achieving successful expression and purification. The antigens were formulated into two distinct vaccine mixtures, Vac A and Vac B, and their protective efficacy was assessed through in vivo challenge experiments. Vac A and Vac B demonstrated high protective efficacies of 100 % and 81.2 %, respectively. Histological analyses revealed reduced tissue damage in vaccinated fish after experimental infection, with Vac A showing no adverse effects, whereas Vac B exhibited mild degenerative changes. Quantitative real-time PCR results showed a significant upregulation of TNF-α and downregulation of IL-1β in the kidneys, spleen, gills, and intestine in both Vac A- and Vac B-immunized fish after challenged with P. koreensis. Additionally, IL-8 exhibits tissue-specific differential expression, with significant upregulation in the kidney, gills, and intestine, and downregulation in the spleen, particularly notable in Vac A-immunized fish. The research underscores the effectiveness of the reverse vaccinology approach in fish and demonstrates the promising potential of Vac A and Vac B as recombinant subunit vaccines.

Screening for Antimicrobial Resistance and Genes of Exotoxins in Pseudomonas aeruginosa Isolates from Infected Dogs and Cats in Poland

Pseudomonas aeruginosa has assumed an increasingly prominent role as the aetiological agent in serious hard-to-treat infections in animals and humans. In this study, 271 P. aeruginosa strains collected from dogs and cats were investigated. The aim of the research was to screen these P. aeruginosa strains for antibiotic resistance and the presence of selected virulence factor genes. Antibiotic resistance was determined using the Kirby-Bauer method, while virulence genes were detected by polymerase chain reaction (PCR). The most frequently detected resistance was to fluoroquinolones, ranging in prevalence from 17.3% for ciprofloxacin up to 83% for enrofloxacin. The resistance to carbapenems was 14% and 4.8% for imipenem and meropenem, respectively. Almost all P. aeruginosa strains harboured the exoT (97.8%) and lasB (93.4%) genes, while the lowest prevalence was found for exoU (17.3%) and plcH (17.3%). P. aeruginosa strains isolated from dogs that harboured the toxA gene were more frequently resistant to ceftazidime (p = 0.012), while the presence of the exoU gene was found to be connected with resistance to marbofloxacin (p = 0.025) and amikacin (p = 0.056). In strains originating from cats, only the connection between the presence of the exoU gene and resistance to enrofloxacin (p = 0.054) was observed. The confirmation of associations between virulence-factor-encoding genes and antibiotic resistance indicates that problems of antibiotic resistance may not only cause complications at the level of antibiotic dosage but also lead to changes in the virulence of the bacteria; thus, further studies in this area are required.

Whole-Genome Sequencing of Pseudomonas koreensis Isolated from Diseased Tor tambroides

Unlike environmental P. koreensis isolated from soil, which has been studied extensively for its role in promoting plant growth, pathogenic P. koreensis isolated from fish has been rarely reported. Therefore, we investigated and isolated the possible pathogen that is responsible for the diseased state of Tor tambroides. Herein, we reported the morphological and biochemical characteristics, as well as whole-genome sequences of a newly identified P. koreensis strain. We assembled a high-quality draft genome of P. koreensis CM-01 with a contig N50 value of 233,601 bp and 99.5% BUSCO completeness. The genome assembly of P. koreensis CM-01 is consists of 6,171,880 bp with a G+C content of 60.5%. Annotation of the genome identified 5538 protein-coding genes, 3 rRNA genes, 54 tRNAs, and no plasmids were found. Besides these, 39 interspersed repeat and 141 tandem repeat sequences, 6 prophages, 51 genomic islands, 94 insertion sequences, 4 clustered regularly interspaced short palindromic repeats, 5 antibiotic-resistant genes, and 150 virulence genes were also predicted in the P. koreensis CM-01 genome. Culture-based approach showed that CM-01 strain exhibited resistance against ampicillin, aztreonam, clindamycin, and cefoxitin with a calculated multiple antibiotic resistance (MAR) index value of 0.4. In addition, the assembled CM-01 genome was successfully annotated against the Cluster of Orthologous Groups of proteins database, Gene Ontology database, and Kyoto Encyclopedia of Genes and Genome pathway database. A comparative analysis of CM-01 with three representative strains of P. koreensis revealed that 92% of orthologous clusters were conserved among these four genomes, and only the CM-01 strain possesses unique elements related to pathogenicity and virulence. This study provides fundamental phenotypic and genomic information for the newly identified P. koreensis strain.

Establishing an Experimental Pseudomonas aeruginosa Keratitis Model in Mice - Challenges and Solutions

BACKGROUND

With the ongoing increase in antimicrobial resistances seen in bacterial isolates causing a keratitis in humans, animal models have become an important tool to study new antimicrobial therapies. Nevertheless, the establishment of experimental keratitis is difficult. Here, we discuss the impact of different arrangements, including animal age, bacterial strain and dose as well as epithelium removal on the outcome of experimental keratitis. We therefore present the methods and results of our establishing experiments.

METHODS

Bacterial load determination and flow cytometry were performed using eye homogenate gained from a 72hours lasting murine Pseudomonas aeruginosa keratitis model. Additionally, the intensity of the infection was scored from 0 to 5, the mice weighed, and blood immune cells counted.

RESULTS

We found that older C57BL/6N mice (8-11 months) are more susceptible to develop a keratitis than younger mice (5-6 weeks). Epithelium removal has no major impact on infectivity and disease progression in aged mice. P. aeruginosa exoU⁺ strains, such as PA54, should preferentially be used and highly concentrated (∼ 5×10⁷ CFU). Establishing an infection with the exoU^- PAO1 derivative DSM 19880 was not possible.

CONCLUSIONS

We present a replicable method to achieve a successful experimental P. aeruginosa keratitis in C57BL/6N mice that is sustained or aggravated over the observation period of 3 days in 80% of all animals tested. Our work is of particular interest to all researchers planning the establishment of such experimental models. We show some key aspects that can simplify and quicken the procedure, ultimately saving costs and animal life.

Pseudomonas aeruginosa: pathogenesis, virulence factors, antibiotic resistance, interaction with host, technology advances and emerging therapeutics

Pseudomonas aeruginosa (P. aeruginosa) is a Gram-negative opportunistic pathogen that infects patients with cystic fibrosis, burn wounds, immunodeficiency, chronic obstructive pulmonary disorder (COPD), cancer, and severe infection requiring ventilation, such as COVID-19. P. aeruginosa is also a widely-used model bacterium for all biological areas. In addition to continued, intense efforts in understanding bacterial pathogenesis of P. aeruginosa including virulence factors (LPS, quorum sensing, two-component systems, 6 type secretion systems, outer membrane vesicles (OMVs), CRISPR-Cas and their regulation), rapid progress has been made in further studying host-pathogen interaction, particularly host immune networks involving autophagy, inflammasome, non-coding RNAs, cGAS, etc. Furthermore, numerous technologic advances, such as bioinformatics, metabolomics, scRNA-seq, nanoparticles, drug screening, and phage therapy, have been used to improve our understanding of P. aeruginosa pathogenesis and host defense. Nevertheless, much remains to be uncovered about interactions between P. aeruginosa and host immune responses, including mechanisms of drug resistance by known or unannotated bacterial virulence factors as well as mammalian cell signaling pathways. The widespread use of antibiotics and the slow development of effective antimicrobials present daunting challenges and necessitate new theoretical and practical platforms to screen and develop mechanism-tested novel drugs to treat intractable infections, especially those caused by multi-drug resistance strains. Benefited from has advancing in research tools and technology, dissecting this pathogen's feature has entered into molecular and mechanistic details as well as dynamic and holistic views. Herein, we comprehensively review the progress and discuss the current status of P. aeruginosa biophysical traits, behaviors, virulence factors, invasive regulators, and host defense patterns against its infection, which point out new directions for future investigation and add to the design of novel and/or alternative therapeutics to combat this clinically significant pathogen.