The intestinal barrier plays an extremely important role in maintaining the immune homeostasis of the gut and the entire body. It is made up of an intricate system of cells, mucus and intestinal microbiota. A complex system of proteins allows the selective permeability of elements that are safe and necessary for the proper nutrition of the body. Disturbances in the tightness of this barrier result in the penetration of toxins and other harmful antigens into the system. Such events lead to various digestive tract dysfunctions, systemic infections, food intolerances and autoimmune diseases. Pathogenic and probiotic bacteria, and the compounds they secrete, undoubtedly affect the properties of the intestinal barrier. The discovery of zonulin, a protein with tight junction regulatory activity in the epithelia, sheds new light on the understanding of the role of the gut barrier in promoting health, as well as the formation of diseases. Coincidentally, there is an increasing number of reports on treatment methods that target gut microbiota, which suggests that the prevention of gut-barrier defects may be a viable approach for improving the condition of COVID-19 patients. Various bacteria–intestinal barrier interactions are the subject of this review, aiming to show the current state of knowledge on this topic and its potential therapeutic applications.

The aim of the work was the evaluation of selected biological and physicochemical, applicative properties of ethylated ascorbic acid (AAE) compared to ascorbic acid (AA). Thermogravimetry (TG), differential thermogravimetry (DTG), and differential thermal analysis (DTA) were conducted, followed by the evaluation of AAE decomposition by the UV-Vis spectroscopic method including the influence of temperature and pH. Scavenging, antimicrobial activity and cytotoxicity against L929 fibroblasts were also performed. The difference in mass loss between AA and AAE was 30% via TG. DTA revealed characteristic exothermic and endothermic effects. The AAE solution was more thermally stable than AA. The calculated zero-order rate constants of free-radical scavenging kinetics for AAE were in the range of 4.9×10(-3)-1.35×10(-2) s(-1). The activation energy for the process was 11,2281 kJ/mol. AAE was active against Staphylococcus (S.) aureus and Enterococcus (E.) faecalis and acted stronger against Candida (C.) albicans than AA. The concentrations of AA ≥2.5% were cytotoxic, whereas in the case of AAE, a 10% concentration was considered cytotoxic. DTG enables the detailed differentiation between AA and AAE. AAE in aqueous solution is more stable compared to AA. The antioxidant activity of AAE is significant. However, the reaction with 2,2-diphenyl-1-picrylhydrazyl (DPPH) indicates prolonged activity compared to AA. Variability in the antimicrobial activity of AAE may find practical application in the pharmaceutical and cosmetic industries. The potential for applicative aims may be supported by the relatively low in vitro toxicity of AAE.

Urinary infections related to the presence of bacterial biofilm on catheters are responsible for loss of patients’ health and, due to their high frequency of occurrence, generate a significant economic burden for hospitals. Klebsiella pneumoniae is a pathogen frequently isolated from this type of infection. In this study, using a cohesive set of techniques performed under stationary and flow conditions, we assessed the ability of 120 K. pneumoniae strains to form biofilm on various surfaces, including catheters, and evaluated the usefulness of clinically applied and experimental compounds to remove biofilm. The results of our study indicate the high impact of intraspecies variability with respect to K. pneumoniae biofilm formation and its susceptibility to antimicrobials and revealed the crucial role of mechanical flushing out of the biofilm from the catheter’s surface with use of locally active antimicrobials. Therefore, our work, although of in vitro character, may be considered an important step in the direction of efficient reduction of K. pneumoniae biofilm-related hospital infections associated with the presence of urine catheters.

The staphylococcal biofilm-based infections of wounds still pose a significant therapeutical challenge. Treated improperly, they increase the risk of limb amputation or even death of the patient. The present algorithms of infected wound treatment include, among others, the application of antiseptic substances. In vitro wound biofilm models are applied in order to scrutinize their activity. In the present work, using a spectrum of techniques, we showed how the change of a single variable (medium composition) in the standard in vitro model translates not only to shift in staphylococcal biofilm features but also to the change of efficacy of clinically applied wound antimicrobials such as octenidine, polyhexamethylene biguanide, chlorhexidine, hypochlorite solutions, and locally applied gentamycin. The data presented in this study may be of a pivotal nature, taking into consideration the fact that results of in vitro analyses are frequently used to propagate application of specific antimicrobials in hospitals and ambulatory care units.

Introduction: Over the past few decades, Klebsiella pneumoniae strains increased their pathogenicity and antibiotic resistance, thereby becoming a major therapeutic challenge. One of the few available therapeutic options seems to be intravenous fosfomycin. Unfortunately, the determination of sensitivity to fosfomycin performed in hospital laboratories can pose a significant problem. Therefore, the aim of the present research was to evaluate the activity of fosfomycin against clinical, multidrug-resistant Klebsiella pneumoniae strains isolated from nosocomial infections between 2011 and 2020, as well as to evaluate the methods routinely used in hospital laboratories to assess bacterial susceptibility to this antibiotic. Materials and Methods: 43 multidrug-resistant Klebsiella strains isolates from various infections were tested. All the strains had ESBL enzymes, and 20 also showed the presence of carbapenemases. Susceptibility was determined using the diffusion method (E-test) and the automated system (Phoenix), which were compared with the reference method (agar dilution). Results: For the reference method and for the E-test, the percentage of strains sensitive to fosfomycin was 65%. For the Phoenix system, the percentage of susceptible strains was slightly higher and stood at 72%. The percentage of fosfomycin-resistant strains in the Klebsiella carbapenemase-producing group was higher (45% for the reference method and E-test and 40% for the Phoenix method) than in carbapenemase-negative strains (25%, 25%, and 20%, respectively). Full (100%) susceptibility categorical agreement was achieved for the E-test and the reference method. Agreement between the automated Phoenix system and the reference method reached 86%. Conclusions: Fosfomycin appears to be the antibiotic with a potential for use in the treatment of infections with multidrug-resistant Klebsiella strains. Susceptibility to this drug is exhibited by some strains, which are resistant to colistin and carbapenems. The E-test, unlike the Phoenix method, can be an alternative to the reference method in the routine determination of fosfomycin susceptibility, as it shows agreement in terms of sensitivity categories and only slight differences in MIC values. The Phoenix system, in comparison to the reference method, shows large discrepancies in the MIC values and in the susceptibility category.