Search Results (8)

Staphylococcus aureus is a vital pathogen causing clinical infections. Capsules are important virulence factors for S. aureus. This study investigates the regulatory mechanisms underlying capsule production in S. aureus. Bacterial strains XN108 and Newman were used, and combined approaches like RNA sequencing (RNA-seq), RT-qPCR, transmission electron microscopy (TEM), gene reporter, and electrophoretic mobility shift assay (EMSA) were performed to test the role and mechanism of WalK(S221P) mutation in S. aureus capsule production. RNA-seq showed an increased expression of cap genes in the WalK(S221P)-carried S. aureus XN108 relative to the mutation-cured XN108-R. TEM and capsular polysaccharide determination demonstrated that XN108 produced more capsules than XN108-R did. Similar results were presented in the WalK(S221P)-contained K-Newman versus the wild-type Newman. RT-qPCR screening showed an increasing expression of the mgrA gene in XN108 versus XN108-R. Gene reporter and EMSA analysis revealed that WalK(S221P) mutation promoted S. aureus capsule production through MgrA. Deletion of mgrA decreased the WalK(S221P)-mediated capsule yield. Moreover, WalK(S221P) mutation remarkably increased the tolerance of S. aureus to whole blood killing and microphage phagocytosis. Overall, these data provide mechanistic insights into the effect of WalK(S221P) on the capsule production of S. aureus, which may set down foundations for future S. aureus virulence investigations. Full article

Streptococcus agalactiae, also known as Group B Streptococcus or GBS, is a commensal colonizer of human vaginal and gastrointestinal tracts that can also be a deadly pathogen for newborns, pregnant women, and the elderly. The SaeRS two-component regulatory system (TCS) positively regulates the expression of two GBS adhesins genes, but its role in the formation of biofilm, an important step in pathogenesis, has not been investigated. In the present study, we set up a novel model of GBS biofilm formation using surfaces coated with human fibrinogen (hFg). Biofilm mass and structure were analyzed by crystal violet staining and three-dimensional fluorescence microscopy, respectively. GBS growth on hFg resulted in the formation of a mature and abundant biofilm composed of bacterial cells and an extracellular matrix containing polysaccharides, proteins, and extracellular DNA (eDNA). Enzymatic and genetic analysis showed that GBS biofilm formation on hFg is dependent on proteins and eDNA in the extracellular matrix and on the presence of covalently linked cell wall proteins on the bacterial surface but not on the type-specific capsular polysaccharide. In the absence of the SaeR regulator of the SaeRS TCS, there was a significant reduction in biomass formation, with reduced numbers of bacterial cells, reduced eDNA content, and disruption of the biofilm architecture. Overall, our data suggest that GBS binding to hFg contributes to biofilm formation and that the SaeRS TCS plays an important role in this process. Full article

Streptococcus suis is a porcine and zoonotic pathogen in the upper respiratory tract, expressing different capsular serotypes and virulence-associated factors. Given its genomic and phenotypic diversity, the virulence potential of S. suis cannot be attributed to a single factor. Since strong inflammatory response is a hallmark of S. suis infection, the objective of this study was to investigate the differences in transcriptional host responses to two serotype 2 and one serotype 9 strains. Both serotypes are frequently found in clinical isolates. We infected porcine precision-cut lung slices (PCLSs) with two serotype 2 strains of high (strain S10) and low (strain T15) virulence, and a serotype 9 strain 8067 of moderate virulence. We observed higher expression of inflammation-related genes during early infection with strains T15 and 8067, in contrast to infection with strain 10, whose expression peaked late. In addition, bacterial gene expression from infected PCLSs revealed differences, mainly of metabolism-related and certain virulence-associated bacterial genes amongst these strains. We conclude that the strain- and time-dependent induction of genes involved in innate immune response might reflect clinical outcomes of infection in vivo, implying rapid control of infection with less virulent strains compared to the highly virulent strain S10. Full article

Biomimetic nanotechnology pertains to the fundamental elements of living systems and the translation of their properties into human applications. The underlying functionalities of biological materials, structures and processes are primarily rooted in the nanoscale domain, serving as a source of inspiration for materials science, medicine, physics, sensor technologies, smart materials science and other interdisciplinary fields. The Biomimetics Special Issues Biomimetic Nanotechnology Vols. 1–3 feature a collection of research and review articles contributed by experts in the field, delving into significant realms of biomimetic nanotechnology. This publication, Vol. 3, comprises four research articles and one review article, which offer valuable insights and inspiration for innovative approaches inspired by Nature’s living systems. The spectrum of the articles is wide and deep and ranges from genetics, traditional medicine, origami, fungi and quartz to green synthesis of nanoparticles. Full article

Klebsiella pneumoniae (K. pneumoniae) induced bovine mastitis has been becoming one of the dominantly pathogenic bacteria in cases of bovine mastitis, and is threatening public health through dairy products. In order to explore the characteristics of multilocus sequence typing (MLST), virulence gene carrying, and the relationship between virulence genes and the antibiotic resistance of Klebsiella pneumoniae from dairy cattle in northern Jiangsu, 208 dairy milk samples were collected from four dairy farms in northern Jiangsu. A total of 68 isolates were obtained through bacterial isolation, purification, and 16S rDNA identification. Eleven virulence genes were detected by specific PCR. The susceptibility of the isolates to antimicrobials was analyzed using the Kirby–Bauer method. The Pearson correlation coefficient was used to analyze the correlation between the presence of virulence genes and the phenotype of drug resistance. ST 2661 was the most prevalent type of K. pneumoniae (13/68, 19.1%) among the 23 ST types identified from the 68 isolates. The virulence gene allS was not detected, but the positive detection rates of the virulence genes fimH, ureA, uge and wabG were 100.0%. Notably, the detection rates of genes rmpA and wcaG, related to the capsular polysaccharide, were 4.4% and 11.8%, respectively, which were lower than those of genes related to siderophores (kfuBC, ybtA and iucB at 50.0%, 23.5%, and 52.9%, respectively). The K. pneumoniae isolates were sensitive to ciprofloxacin, nitrofurantoin, and meropenem. However, the resistance rate to penicillin was the highest (58/68, 85.3%), along with resistance to amoxicillin (16/68, 23.5%). The results revealed the distribution of 23 ST types of K. pneumoniae from the milk from bovine-mastitis-infected dairy cows in northern Jiangsu, and the expression or absence of the virulence gene kfuBC was related to the sensitivity to antibiotics. The current study provides important information relating to the distribution and characteristics of K. pneumoniae isolated from dairy cows with clinical bovine mastitis, and is indicative of strategies for improving the treatment of K. pneumoniae-induced bovine mastitis. Full article

The biofilm is a conglomerate of cells surrounded by an extracellular matrix, which contributes to the persistence of infections. The difficulty in removing the biofilm drives the research for new therapeutic options. In this work, the effect of terpenes (−)-trans-Caryophyllene, (S)-cis-Verbenol, (S)-(−)-Limonene, (R)-(+)-Limonene, and Linalool was evaluated, individually and in combinations on bacterial growth, by assay with resazurin; the formation of biofilm, by assay with violet crystal; and the expression of associated genes, by real-time PCR, in two clinical isolates of Staphyloccocus aureus, ST30-t019 and ST5-t311, responsible for more than 90% of pediatric infections by this pathogen in Paraguay. All combinations of terpenes can inhibit biofilm formation in more than 50% without affecting bacterial growth. The most effective combination was (−)-trans-Caryophyllene and Linalool at a 500 μg/mL concentration for each, with an inhibition percentage of 88%. This combination decreased the expression levels of the sdrD, spa, agr, and hld genes associated with the initial cell adhesion stage and quorum sensing. At the same time, it increased the expression levels of the cap5B and cap5C genes related to the production of capsular polysaccharides. The combinations of compounds tested are promising alternatives to inhibit biofilm formation in S. aureus. Full article

Klebsiella pneumoniae is among the leading bacteria that cause nosocomial infections. The capsule of this Gram-negative bacterium is a dominant virulence factor, with a prominent role in defense and biofilm formation. Bacteriophages, which are specific for one bacterial strain and its capsule type, can evoke the lysis of bacterial cells, aided by polysaccharide depolymerase enzymes. In this study, we isolated and characterized a bacteriophage against the nosocomial K. pneumoniae 52145 strain with K2 capsular serotype. The phage showed a narrow host range and stable lytic activity, even when exposed to different temperatures or detergents. Preventive effect of the phage in a nasal colonization model was investigated in vivo. Phlyogenetic analysis showed that the newly isolated Klebsiella phage B1 belongs to the Webervirus genus in Drexlerviridae family. We identified the location of the capsule depolymerase gene of the new phage, which was amplified, cloned, expressed, and purified. The efficacy of the recombinant B1dep depolymerase was tested by spotting on K. pneumoniae strains and it was confirmed that the extract lowers the thickness of the bacterium lawn as it degrades the protective capsule on bacterial cells. As K. pneumoniae strains possessing the K2 serotype have epidemiological importance, the B1 phage and its depolymerase are promising candidates for use as possible antimicrobial agents. Full article

In this study, we developed tigecycline resistance in Klebsiella pneumoniae ST23 strains in vitro and investigated the change in virulence associated with hypermucoviscosity. In vitro-induced tigecycline-resistant (TGC-IR) K. pneumoniae mutants were obtained from three tigecycline-susceptible (TGC-S) strains, belonging to ST23 and serotype K1, by culturing in media with tigecycline in a stepwise manner. An antimicrobial susceptibility test, string test, mucoviscosity assay, and capsular polysaccharide (CPS) quantification were performed. Biofilm formation and serum resistance were evaluated, and survival rates of bacterial strains in fruit flies and macrophages were measured. Alterations of rpsJ, ramR, soxR, acrR, and marR genes were investigated and the expression levels of ramA and efflux pump genes were evaluated. The hypermucoviscosity phenotype was dramatically decreased in the TGC-IR mutants. Reduced CPS production in TGC-IR mutants was also identified. Increased resistance to most other antimicrobial agents was found in TGC-IR mutants. In addition, the TGC-IR mutants exhibited reduced biofilm formation, low serum resistance, and decreased survival rates within fruit flies and macrophages. Our study shows that development of tigecycline resistance in hypervirulent K. pneumoniae strains result in defects in virulence associated with hypermucoviscosity. Full article