Microbial pathogenesis最新文献

The present study was aimed to assess and validate the safety and functional efficacy of an indigenous probiotic strain Limosilactobacillus fermentum NCDC 400 (hereafter, LFN400) in an immunocompromised murine model. The study included four groups; a normal control (NC) group without immune suppression; an experimental model control (MC) with immune suppression induced via intraperitoneal cyclophosphamide (Cy) administration; and two MC groups orally administered with either low dose (LD) or high dose (HD) of LFN400 at dose 10⁸ and 10¹⁰ CFU/mouse/day, respectively, for 15-days. Both control groups received normal saline as placebo control. LFN400 improved specific experimental characteristics including hematological and serum biochemical markers. Compared to MC group, LFN400-fed groups showed markedly (P < 0.05) decreased arrays of detrimental caecal enzymes. We did not observe instances of bacterial translocation of LFN400 from gut to bloodstream or extra-intestinal organs. LFN400 intake significantly (P < 0.05) enhanced spleen cell differentiation, immune and oxidative stress markers, and restored Cy-induced histopathological changes in multiple tissues, including the spleen. There was no genotoxic effect of LFN400 on bone marrow cells. Although not statistically significant, LFN400 feeding moderately increased gut microbiome diversity, supporting the growth of beneficial saccharolytic microorganisms and reducing the presence of pathobionts. The findings demonstrate that the probiotic strain LFN400 possesses in vivo safety and immunomodulatory potency and thus should be considered a potential candidate for future human clinical studies.

Sonodynamic antimicrobial chemotherapy (SACT), as a novel anti-infective program, has received tremendous attention due to its good tissue penetration depth and low invasion. Ultrasound (US) frequency was one of the important parameters for SACT. To investigate the influence of different US frequencies on sonodynamic antimicrobial activity of ciprofloxacin-capped gold nanoparticles (CIP:GNPs). C. albicans and E. coli were chosen as the action objects. The bacterial survival rate was used in the assessment index and measured by plate colony-counting methods. The reactive oxygen species (ROS) produced under US irradiation were detected by ROS fluorescence probe and used to analyze the sonodynamic antibacterial mechanism of CIP:GNPs following different US frequencies. High-frequency US combined with CIP:GNPs had a good synergistic antimicrobial impact on C. albicans, while medium-frequency US showed a strong effect on E. coli. Moreover, the mechanism research experiment proved that intracellular ROS levels were closely related to changes in US frequency, and significantly affected the synergistic activity of CIP:GNPs. The injury of E. coli appearance showed more sensitivity to the change of US frequency than that of C. albicans, but its action laws were relatively complicated and needed to be further studied.

Staphylococcus aureus is the most common cause of serious health conditions because of the formation of biofilm, which lowers antibiotic efficacy and enhances infection transmission and tenacious behavior. This bacteria is a major threat to the worldwide healthcare system. Silver nanoparticles have strong antibacterial characteristics and emerged as a possible alternative. This work is most relevant since it investigates the parameters influencing the biogenic nanoparticle-assisted control of bacterial biofilms by Staphylococcus aureus.

Nanoparticles were fabricated utilizing Hellenia speciosa rhizome extracts, which largely comprised physiologically active components such as spirost-5-en-3-yl acetate, thymol, stigmasterol, and diosgenin, enhanced with the creation of silver nanocomposites. GC-MS, XRD, DLS, SEM, EDX, FTIR and TEM were used to investigate the characteristics of nanoparticles. The microtiter plate experiment showed that nanoparticles destroyed biofilms by up to 92.41 % at doses that ranged from 0 to 25 μg/ml. Fluorescence microscopy and SEM demonstrated the nanoparticles' capacity to prevent bacterial surface adhesion. EDX research revealed that the organic extract efficiently formed silver nanoparticles with considerable oxygen incorporation, which was attributed to phytochemicals that stabilize AgNPs and prevent accumulation. FTIR spectroscopy indicated the existence of hydroxyl, carbonyl, and carboxylate groups, which are essential for nanoparticle stability. TEM revealed that the AgNPs were spheroidal, with diameters ranging from 40 to 60 nm and an average of 46 nm. These results demonstrate the efficacy of H. speciosa extract in creating stable, well-defined AgNPs suited for a variety of applications. This work underlines the potential of green-synthesized AgNPs in biomedical applications, notably in the treatment of S. aureus biofilm-associated illnesses. The thorough characterization gives important information on the stability and efficiency of these biogenic nanoparticles.

Background

The increasing prevalence of antibiotic-resistant bacterial infections has led to the search for new approaches.

Objective

This study aimed to evaluate the effects of carvacrol and N-acetyl cysteine, both individually and in combination, on the planktonic cells and biofilm formations of Staphylococcus aureus, including methicillin-resistant and methicillin-sensitive strains. Additionally, the study sought to perform cytotoxicity tests and chemical characterization to further understand the properties and potential applications of these substances.

Methods

A total of 19 S. aureus strains were included in the study. Minimum inhibitory concentration and minimum bactericidal concentration were determined by assays. Synergy analysis tests were carried out. Cytotoxicity tests were conducted on the fibroblast cell line. Characterization test was performed.

Results

While Minimum inhibitory concentration and minimum bactericidal concentration values for carvacrol varied between 250 and 500 μg/ml, these values were in the range of 32–64 mg/ml for N-acetyl cysteine. Biofilm formation activities were identified. A total of eight strains, including six clinical and two standard strains with the highest biofilm-forming ability, were selected for combination studies. The combination of Carvacrol and N-acetyl cysteine exhibited synergistic and partially synergistic effects on the tested planktonic and biofilm strains, and these effects were dose-dependent. Carvacrol was found to be the most active drug at the end of 24, 48, and 72 h. Regarding the synergistic effect of N-acetyl cysteine + carvacrol, it was revealed to exhibit higher activity than N-acetyl cysteine and lower activity than carvacrol.

Conclusion

The combination of carvacrol and N-acetyl cysteine demonstrated synergistic and partially synergistic effects against both planktonic and biofilm forms of Staphylococcus aureus. These results suggest potential for novel approaches in managing orthopedic infections, warranting further research to explore their therapeutic applications.

The aim of this study was to investigate both the microbial composition and absolute abundance of clinically relevant bacteria in tissue specimens from patients with chronic suppurative otitis media with cholesteatoma (CSOM with cholesteatoma). Mastoid mucosa and cholesteatoma tissue from eleven subjects with CSOM with cholesteatoma, and mastoid mucosa from ten controls were examined using standard hospital culture swabs, Gram staining, bacterial 16S rRNA gene sequencing, Droplet Digital PCR (ddPCR), and multiplex PCR. Positive results from culture swabs were reported in half the CSOM with cholesteatoma samples and 1 control sample. In contrast, ddPCR detected bacterial genes copies in all 11 mucosa and cholesteatoma of CSOM subjects and 3 control samples. The average bacterial gene copies in tissue samples with CSOM with cholesteaotoma (1.6 ± 0.7 log10) was significantly higher compared to healthy controls (0.3 ± 1.6). These results were corroborated with Gram-staining that identified the large presence of Gram-positive cocci cells in the cholesteatoma tissue of CSOM subjects which were not seen in the mucosa of controls. The most abundant genus detected by sequencing in the mucosa and cholesteatoma of CSOM samples was Anaerococcus (93.5 % of all reads), and genus Meiothermus (0.9 %) in the control sample. The 3 samples with the highest sequencing reads (>300) were further analysed using multiplex PCR to identify the dominant Anaerococcus species. Anaerococcus hydrogenalis was the dominant species identified in these samples. In contract, commonly named ear pathogens, genera Staphylococcus and Pseudomonas, were detected in low numbers (<0.001 % of all sequencing reads) and low prevalence (2/16 samples) in the tissue samples of this study.

The results show that culture severely underestimated the bacterial diversity in CSOM samples and investigating tissue rather than standard culture swabs might be advantageous to understanding the disease process. The high abundance of bacteria and the large presence of Gram-positive cells detected in the cholesteatoma tissue of CSOM compared to mucosa of CSOM or controls could be members from the genus Anaerococcus. Anaerococcus may well be a pathogen in CSOM with cholesteatoma, but their role in this condition requires further investigation.

Candida albicans (C. albicans) biofilm infections are quite difficult to manage due to their resistance against conventional antifungal drugs. To address this issue, there is a desperate need for new therapeutic drugs. In the present study, a green and efficient protocol has been developed for the synthesis of 2-amino-4H-pyran-3-carbonitrile scaffolds 4a-i, 6a-j, and 8a-g by Knoevenagel-Michael-cyclocondensation reaction between aldehydes, malononitrile, and diverse enolizable C-H activated acidic compounds using guanidinium carbonate as a catalyst either under grinding conditions or by stirring at room temperature. This protocol is operationally simple, rapid, inexpensive, has easy workup and column-free purification. A further investigation of the synthesized compounds was conducted to examine their antifungal potential and their ability to inhibit the growth and development of biofilm-forming yeasts like fungus C. albicans. According to our findings, 4b, 4d, 4e, 6e, 6f, 6g, 6i, 8c, 8d, and 8g were found to be active and potential inhibitors for biofilm infection causing C. albicans. The inhibition of biofilm by active compounds were observed using field emission scanning electron microscopy (FESEM). Biofilm inhibiting compounds were also tested for in vitro toxicity by using 3T3-L1 cell line, and 4b, 6e, 6f, 6g, 6i, 8c, and 8d were found to be biocompatible. Furthermore, the in silico ADME descriptors revealed drug-like properties with no violation of Lipinski's rule of five. Hence, the result suggested that synthesized derivatives could serve as a useful aid in the development of novel antifungal compounds for the treatment of fungal infections and virulence in C. albicans.

Duck spleen marble-like necrosis disease (DSMND) has been prevalent in Chinese duck farms since 2016. The etiological study was carried out in this study using etiological detection, pathogen isolation, whole genome sequencing, and artificial infection test. A highly pathogenic Riemerella anatipestifer (RA) strain was determined as the etiologic agent. Phylogenomic analysis showed that this RA strain was closely related to duck origin RA strain RCAD0421 and chicken origin RA strain S63. The clinical symptoms and pathological changes of artificial infection ducks were similar to those of clinical cases. This is the first identification of RA as the pathogen of DSMND, which provides a theoretical basis for this disease’ s prevention and control.

A priori, early exposure to a wide range of bacteria, viruses, and parasites appears to fortify and regulate the immune system, potentially reducing the risk of autoimmune diseases. However, improving hygiene conditions in numerous societies has led to a reduction in these microbial exposures, which, according to certain theories, could contribute to an increase in autoimmune diseases. Indeed, molecular mimicry is a key factor triggering immune system reactions; while it seeks pathogens, it can bind to self-molecules, leading to autoimmune diseases associated with microbial infections. On the other hand, a hygiene-based approach aimed at reducing the load of infectious agents through better personal hygiene can be beneficial for such pathologies. This review sheds light on how the evolution of the innate immune system, following the evolution of molecular patterns associated with microbes, contributes to our protection but may also trigger autoimmune diseases linked to microbes. Furthermore, it addresses how hygiene conditions shield us against autoimmune diseases related to microbes but may lead to autoimmune pathologies not associated with microbes.

This report aims to describe the identification of porcine astrovirus 3 (PAstV3) RNA in the central nervous system (CNS) of weaned pigs with clinical signs of neurological disease associated with polioencephalomyelitis in southeastern Brazil. Three, 20 -35 days-old piglets that died after clinical manifestations of a neurological syndrome were submitted to post-mortem evaluations. Tissue samples were examined by histopathology, bacteriology, and molecular assays (RT-PCR, nested-PCR, RT-qPCR, and Sanger sequencing) to detect the primary infectious disease agents associated with neurological disease in pigs. The principal neuropathological alterations occurred in the grey matter of the spinal cord and brainstem resulting in nonsuppurative poliomyelitis and rhombencephalitis. PAstV3 RNA was detected in the CNS samples of all piglets with histopathological evidence of disease and was confirmed by nucleotide sequencing. Nucleic acids from pathogens commonly associated with neurological diseases in pigs, such as porcine teschovirus, porcine sapelovirus, porcine enterovirus G, atypical porcine pestivirus, senecavirus A, and encephalomyocarditis virus was not detected by molecular assays in the three piglets. This is the first report of PAstV3 in piglets with neurological disease and lesions consistent with polioencephalomyelitis in Brazil. This report highlights the importance of monitoring health events that could compromise pig farming productivity and animal welfare.

The switch to alternate cell types by Staphylococcus aureus creates sub-populations even within an active population, that are highly resilient, tolerant to antibiotics and lack clinical symptoms of infection. These cells present a challenge for clinical treatment where even after initial intervention has seemingly cleared the infection, these alternate cell types persist within tissue to revert and cause disease. Small colony variants (SCV) are a cell type which facilitate persistent infection but clinically isolated SCVs are often unstable in laboratory conditions. We have isolated a pair of S. aureus isolates from an individual patient with osteomyelitis presenting with heterogenous phenotypes; a stable SCV (sSCV) and a SCV that reverts upon laboratory culturing to the usual, active and non-SCV cell type. Thus we are able use this pair to investigate and compare the genetic mechanisms that underlie the clinical variatons of SCV phenotype. The switch to the sSCV phenotype was associated with frameshift mutations in the enolase eno and the histidine kinase arlS. The phenoptye of the sSCV was an impeded growth dependent on amino acid catabolism and modulated biofilm. These mutations present potentially a new molecular mechanism which confer persistence within osteomyelitis.