Streptococcus salivarius as an Important Factor in Dental Biofilm Homeostasis: Influence on Streptococcus mutans and Aggregatibacter actinomycetemcomitans in Mixed Biofilm

A disturbed balance within the dental biofilm can result in the dominance of cariogenic and periodontopathogenic species and disease development. Due to the failure of pharmacological treatment of biofilm infection, a preventive approach to promoting healthy oral microbiota is necessary. This study analyzed the influence of Streptococcus salivarius K12 on the development of a multispecies biofilm composed of Streptococcus mutans, S. oralis and Aggregatibacter actinomycetemcomitans. Four different materials were used: hydroxyapatite, dentin and two dense polytetrafluoroethylene (d-PTFE) membranes. Total bacteria, individual species and their proportions in the mixed biofilm were quantified. A qualitative analysis of the mixed biofilm was performed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results showed that in the presence of S. salivarius K 12 in the initial stage of biofilm development, the proportion of S. mutans was reduced, which resulted in the inhibition of microcolony development and the complex three-dimensional structure of the biofilm. In the mature biofilm, a significantly lower proportion of the periodontopathogenic species A. actinomycetemcomitans was found in the salivarius biofilm. Our results show that S. salivarius K 12 can inhibit the growth of pathogens in the dental biofilm and help maintain the physiological balance in the oral microbiome.

Disinfecting Action of Gaseous Ozone on OXA-48-Producing Klebsiella pneumoniae Biofilm In Vitro

Klebsiella pneumoniae is an emerging multidrug-resistant pathogen that can contaminate hospital surfaces in the form of a biofilm which is hard to remove with standard disinfectants. Because of biofilm resistance to conservative disinfectants, the application of new disinfection technologies is becoming more frequent. Ozone gas has antimicrobial activity but there is lack of data on its action against K. pneumoniae biofilm. The aim of this study was to investigate the effects and mechanisms of action of gaseous ozone on the OXA-48-procuding K. pneumoniae biofilm. A 24 h biofilm of K. pneumoniae formed on ceramic tiles was subsequently exposed to different concentrations of ozone during one and two hours to determine the optimal ozone concentration. Afterwards, the total bacteria count, total biomass and oxidative stress levels were monitored. A total of 25 ppm of gaseous ozone was determined to be optimal ozone concentration and caused reduction in total bacteria number in all strains of K. pneumoniae for 2.0 log₁₀ CFU/cm², followed by reduction in total biomass up to 88.15%. Reactive oxygen species levels significantly increased after the ozone treatment at 182% for the representative K. pneumoniae NCTC 13442 strain. Ozone gas in the concentration of 25 ppm caused significant biofilm reduction but did not completely eradicate the K. pneumoniae biofilm formed on ceramics. In conclusion, ozone gas has great potential to be used as an additional hygiene measure in joint combat against biofilm in hospital environments.

Granulysin expression and granulysin-mediated apoptosis in the peripheral blood of osteoarthritis patients

Osteoarthritis (OA) is a chronic joint disease caused by mechanical damage and metabolic factors that support the development of low-grade inflammation. Increased levels of T helper 1 pro-inflammatory cytokines in the serum of OA patients may support granulysin (GNLY) mediated cytotoxicity, which in-turn may contribute to the pathogenesis of OA. In the present study, GNLY expression and cytotoxic/apoptotic mechanisms mediated by GNLY in the peripheral blood of OA patients were assessed. A total of 40 non-obese women (median age of 64 years old) with knee OA, and 40 controls (median age 62 years old) were enrolled in the study. GNLY, IFN-γ and IL-4 expression levels were investigated in peripheral blood lymphocytes (PBLs) using flow cytometry, immunocytochemistry and/or confocal microscopy. Natural killer (NK) GNLY-mediated apoptosis through NK effectors against K-562 targets was analyzed using the PKH-26 18-h cytotoxicity assay. Serum GNLY levels were assessed using ELISA. The percentage of GNLY⁺PBLs was higher in the OA patients than that in the controls due to the increase in the proportions of GNLY⁺ cells in the natural killer (NK), T and natural killer T (NKT) subsets. GNLY localization inside exocytotic lysosomal-associated membrane protein-1⁺ granules was ~40% in both groups. However, the intensity of GNLY labeling in PBLs was higher in OA patients than in the controls, and it was supported by the increased expression of IFN-γ relative to IL-4 in NK and T cells from OA patients. The serum GNLY concentration was <0.3 ng/ml in both groups. RC8 anti-GNLY mAb by itself was unable to significantly alter early apoptosis, whereas RC8 anti-GNLY mAb combined with anti-perforin mAb significantly reduced NK-mediated early apoptosis of K-562 targets in the OA patients, whilst not exerting a notable effect in the controls. Anti-perforin mAb by itself did not affect apoptosis significantly. These results suggest that in women with knee OA, GNLY expression in the PBL subsets and GNLY-mediated early apoptosis of K-562 targets are increased compared with the controls and accompanied by intracellular dominance of IFN-γ over IL-4 in NK cells.

Cytomegalovirus Generates Assembly Compartment in the Early Phase of Infection by Perturbation of Host-Cell Factors Recruitment at the Early Endosome/Endosomal Recycling Compartment/Trans-Golgi Interface

Beta-herpesviruses develop a unique structure within the infected cell known as an assembly compartment (AC). This structure, as large as the nucleus, is composed of host-cell-derived membranous elements. The biogenesis of the AC and its contribution to the final stages of beta-herpesvirus assembly are still unclear. In this study, we performed a spatial and temporal analysis of the AC in cells infected with murine CMV (MCMV), a member of the beta-herpesvirus family, using a panel of markers that characterize membranous organelle system. Out of 64 markers that were analyzed, 52 were cytosolic proteins that are recruited to membranes as components of membrane-shaping regulatory cascades. The analysis demonstrates that MCMV infection extensively reorganizes interface between early endosomes (EE), endosomal recycling compartment (ERC), and the trans-Golgi network (TGN), resulting in expansion of various EE-ERC-TGN intermediates that fill the broad area of the inner AC. These intermediates are displayed as over-recruitment of host-cell factors that control membrane flow at the EE-ERC-TGN interface. Most of the reorganization is accomplished in the early (E) phase of infection, indicating that the AC biogenesis is controlled by MCMV early genes. Although it is known that CMV infection affects the expression of a large number of host-cell factors that control membranous system, analysis of the host-cell transcriptome and protein expression in the E phase of infection demonstrated no sufficiently significant alteration in expression levels of analyzed markers. Thus, our study demonstrates that MCMV-encoded early phase function targets recruitment cascades of host cell-factors that control membranous flow at the EE-ERC-TGN interface in order to initiate the development of the AC.