is a microorganism resident in the skin and nasal membranes with a dreadful pathogenic potential to cause a variety of community and hospital-acquired infections. The frequency of these infections is ...increasing and their treatment is becoming more difficult. The ability of
to form biofilms and the emergence of multidrug-resistant strains are the main reasons determining the challenge in dealing with these infections.
infectious capacity and its success as a pathogen is related to the expression of virulence factors, among which the production of a wide variety of toxins is highlighted. For this reason, a better understanding of
toxins is needed to enable the development of new strategies to reduce their production and consequently improve therapeutic approaches. This review focuses on understanding the toxin-based pathogenesis of
and their role on infectious diseases.
This study evaluated the effects of bone marrow-derived mesenchymal stem cells (BMSCs) or their conditioned medium (CM) on the repair and prevention of Acute Kidney Injury (AKI) induced by gentamicin ...(G). Animals received daily injections of G up to 20 days. On the 10(th) day, injections of BMSCs, CM, CM+trypsin, CM+RNase or exosome-like microvesicles extracted from the CM were administered. In the prevention groups, the animals received the BMSCs 24 h before or on the 5(th) day of G treatment. Creatinine (Cr), urea (U), FENa and cytokines were quantified. The kidneys were evaluated using hematoxylin/eosin staining and immunohystochemistry. The levels of Cr, U and FENa increased during all the periods of G treatment. The BMSC transplantation, its CM or exosome injections inhibited the increase in Cr, U, FENa, necrosis, apoptosis and also increased cell proliferation. The pro-inflammatory cytokines decreased while the anti-inflammatory cytokines increased compared to G. When the CM or its exosomes were incubated with RNase (but not trypsin), these effects were blunted. The Y chromosome was not observed in the 24-h prevention group, but it persisted in the kidney for all of the periods analyzed, suggesting that the injury is necessary for the docking and maintenance of BMSCs in the kidney. In conclusion, the BMSCs and CM minimized the G-induced renal damage through paracrine effects, most likely through the RNA carried by the exosome-like microvesicles. The use of the CM from BMSCs can be a potential therapeutic tool for this type of nephrotoxicity, allowing for the avoidance of cell transplantations.
Antibiotic resistance has been increasingly reported for a wide variety of bacteria of clinical significance. This widespread problem constitutes one of the greatest challenges of the twenty-first ...century. Faced with this issue, clinicians and researchers have been persuaded to design novel strategies in order to try to control pathogenic bacteria. Therefore, the discovery and elucidation of the mechanisms underlying bacterial pathogenesis and intercellular communication have opened new perspectives for the development of alternative approaches. Antipathogenic and/or antivirulence therapies based on the interruption of quorum sensing pathways are one of several such promising strategies aimed at disarming rather than at eradicating bacterial pathogens during the course of colonization and infection. This review describes mechanisms of bacterial communication involved in biofilm formation. An overview of the potential of marine bacteria and their bioactive components as QS inhibitors is further provided.
Single- and multispecies biofilms formed by six drinking water-isolated bacterial species were used to assess their susceptibilities to sodium hypochlorite (SHC). In general, multispecies biofilms ...were more resistant to inactivation and removal than single biofilms. Total biofilm inactivation was achieved only for Acinetobacter calcoaceticus single-species biofilms and for those multispecies biofilms without A. calcoaceticus. Biofilms with all bacteria had the highest resistance to SHC, while those without A. calcoaceticus were the most susceptible. A. calcoaceticus formed single biofilms susceptible to SHC; however, its presence in multispecies biofilms increased their resistance to disinfection.
Concerns on the presence of emerging contaminants (ECs) in water sources have increased in recent years. The lack of efficient technologies to remove ECs from residual waters contributes for their ...appearance in drinking water distribution systems (DWDS). Therefore, sessile microorganisms on DWDS pipes are continuously exposed to trace concentrations of ECs. However, no data exists on the role of ECs on the resident microbiota. The present work aims to understand the effects of prolonged exposure of a bacterial strain of Stenotrophomonas maltophilia, isolated from a DWDS, in both planktonic and biofilm states, to trace concentrations of selected ECs (antipyrine–ANTP; diclofenac sodium salt–DCF; ibuprofen–IBP; galaxolide–GAL; tonalide–TON; carbamazepine–CBZ; clofibric acid–CA; tylosin–TY) on its tolerance to sodium hypochlorite (NaOCl) and resistance to antibiotics. Pre-established S. maltophilia biofilms were exposed to ECs for 26 d. Subsequently, the planktonic behaviour of the biofilm cells grown in the presence of ECS was characterized in terms of susceptibility to NaOCl and to selected antibiotics (levofloxacin and trimethoprim-sulfamethoxazole). Moreover, S.maltophilia was tested on its biofilm productivity in the presence of ECs (alone and mixed). These biofilms were challenged by NaOCl in order to assess the role of ECs on biofilm susceptibility. The results did not evidence remarkable effects of ECs on planktonic S. maltophilia susceptibility to NaOCl and antibiotics. However, S. maltophilia biofilm production and susceptibility to NaOCl was affected from ECs pre-exposure, particularly by the combination of different ECs (CA + CBZ, CA + IBP, CA + CBZ + IBP). S. maltophilia biofilms became more resistant to removal by NaOCl when developed in the presence of mixtures of CA + CBZ and CA + CBZ + IBP. Also, biofilm production was significantly affected. CA was present in all the combinations that altered biofilm behaviour. The overall results propose that exposure to ECs for 26 days had not a huge impact on S. maltophilia planktonic antimicrobial susceptibility. Nevertheless, the prolonged exposure to some ECs altered biofilm production and tolerance to NaOCl, with a potential practical outcome of hindering DWDS disinfection. The simultaneous presence of different ECs in the environment may amplify biofilm resilience.
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•Exposure to ECs had no significant effect on S. maltophilia tolerance to antibiotics.•The combination of CA, CBZ and/or IBP affected biofilm production.•The combination of CA, CBZ and/or IBP increased biofilm tolerance to NaOCl.•The exposure to ECs may hinder chlorine efficient in terms of biofilm control.
In the environment, multiple microorganisms coexist as communities, competing for resources and often associated as biofilms. In this study, single- and dual-species biofilm formation by, and ...specific activities of, six heterotrophic intergeneric bacteria were determined using 96-well polystyrene plates over a 72-h period. These bacteria were isolated from drinking water and identified by partial 16S rRNA gene sequencing. A series of planktonic studies was also performed, assessing the bacterial growth rate, motility, and production of quorum-sensing inhibitors (QSI). This constituted an attempt to identify key attributes allowing bacteria to effectively interact and coexist in a drinking-water environment. We observed that in both pure and dual cultures, all of the isolates formed stable biofilms within 72 h, with specific metabolic activity decreasing, in most cases, with an increase in biofilm mass. The largest single- and dual-biofilm amounts were found for Methylobacterium sp. and the combination of Methylobacterium sp. and Mycobacterium mucogenicum, respectively. Evidences of microbial interactions in dual-biofilm formation, associated with appreciable biomass variation in comparison with single biofilms, were found for the following cases: synergy/cooperation between Sphingomonas capsulata and Burkholderia cepacia, S. capsulata and Staphylococcus sp., and B. cepacia and Acinetobacter calcoaceticus and antagonism between S. capsulata and M. mucogenicum, S. capsulata and A. calcoaceticus, and M. mucogenicum and Staphylococcus sp. A neutral interaction was found for Methylobacterium sp.-M. mucogenicum, S. capsulata-Staphylococcus sp., M. mucogenicum-A. calcoaceticus, and Methylobacterium sp.-A. calcoaceticus biofilms, since the resultant dual biofilms had a mass and specific metabolic activity similar to the average for each single biofilm. B. cepacia had the highest growth rate and motility and produced QSI. Other bacteria producing QSI were Methylobacterium sp., S. capsulata, and Staphylococcus sp. However, only for S. capsulata-M. mucogenicum, S. capsulata-A. calcoaceticus, and M. mucogenicum-Staphylococcus sp., dual-biofilm formation seems to be regulated by the QSI produced by S. capsulata and Staphylococcus sp. and by the increased growth rate of S. capsulata. The parameters assessed by planktonic studies did not allow prediction and generalization of the exact mechanism regulating dual-species biofilm formation between the drinking-water bacteria.
The development of anthropogenic activities has led to an excessive disposal of wastes into water bodies, thus reducing water quality and damaging aquatic ecosystems. To avoid the negative impacts ...associated to the discharge of wastes into water courses, effective remediation processes are required to reduce nitrogen and phosphorus concentrations in discharged effluents. Current methodologies applied for nutrients removal tend to be complex, expensive and energy demanding. Therefore, cultivation of microalgae has appeared as an emerging alternative for nutrients removal from wastewaters. These photosynthetic microorganisms require large amounts of nitrogen and phosphorus for their growth. However, since it is very difficult to maintain pure cultures of these microorganisms in wastewater treatment processes, several studies have reported the use of natural and artificial microalgal consortia composed exclusively by microalgae or by microalgae and bacteria. The use of these consortia in the remediation of wastewaters can be very advantageous because: (i) cooperative interactions between the co-cultivated microorganisms can occur, enhancing the overall uptake of nutrients; and (ii) these systems tend to be more resistant to environmental conditions oscillations. This study provides an updated review of the literature regarding the application of microalgal consortia in the remediation of wastewaters from different sources, focusing on the mechanisms involved in nutrients removal by microalgae and the main interactions established between the microorganisms integrating the consortia and how they can influence nutrients removal efficiencies.
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•Microalgal consortia can be effectively applied in wastewater remediation.•Cooperative interactions between these microorganisms rule nutrients uptake rates.•Microalgal consortia can integrate the tertiary treatment step.•Microalgal-bacterial consortia can replace secondary and tertiary treatment steps.
Microbial adhesion to surfaces and the consequent biofilm formation has been documented in many different environments. Biofilms constitute a protected mode of growth that allows microorganisms to ...survival in hostile environments, being their physiology and behavior significantly different from their planktonic counterparts. In dairy industry, biofilms may be a source of recalcitrant contaminations, causing food spoilage and are possible sources of public health problems such as outbreaks of foodborne pathogens. Biofilms are difficult to eradicate due to their resistant phenotype. However, conventional cleaning and disinfection regimens may also contribute to inefficient biofilm control and to the dissemination of resistance. Consequently, new control strategies are constantly emerging with main incidence in the use of biosolutions (enzymes, phages, interspecies interactions and antimicrobial molecules from microbial origin).
The present review will focus on describing the mechanisms involved in biofilm formation and behavior, deleterious effects associated with their presence, and some of the current and emergent control strategies, providing new insight of concern for food industry.
The increased resistance of pathogenic microorganisms is frequently attributed to the extreme and inadequate use of antibiotics and transmission of resistance within and between individuals. To ...counter the emergence of resistant microorganisms, considerable resources have been invested in the search for new antimicrobials. Plants synthesize a diverse array of secondary metabolites (phytochemicals) known to be involved in defense mechanisms, and in the last few years it is recognized that some of these molecules have health beneficial effects, including antimicrobial properties. In this study, the mechanism of action of gallic (GA) and ferulic (FA) acids, a hydroxybenzoic acid and a hydroxycinnamic acid, was assessed on Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Listeria monocytogenes. The targets of antimicrobial action were studied using different bacterial physiological indices: minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), membrane permeabilization, intracellular potassium release, physicochemical surface properties, and surface charge. It was found that FA and GA had antimicrobial activity against the bacteria tested with MIC of 500 μg/mL for P. aeruginosa, 1500 μg/mL for E. coli, 1750 μg/mL for S. aureus, and 2000 μg/mL for L. monocytogenes with GA; 100 μg/mL for E. coli and P. aeruginosa, 1100 μg/mL and 1250 μg/mL for S. aureus and L. monocytogenes, respectively, with FA. The MBC for E. coli was 2500 μg/mL (FA) and 5000 (GA), for S. aureus was 5000 μg/mL (FA) and 5250 μg/mL (GA), for L. monocytogenes was 5300 μg/mL (FA) and 5500 μg/mL (GA), and 500 μg/mL for P. aeruginosa, with both phytochemicals. GA and FA led to irreversible changes in membrane properties (charge, intra and extracellular permeability, and physicochemical properties) through hydrophobicity changes, decrease of negative surface charge, and occurrence of local rupture or pore formation in the cell membranes with consequent leakage of essential intracellular constituents. The overall study emphasizes the potential of plant-derived molecules as a green and sustainable source of new broad spectrum antimicrobial products.
Biofilms constitute a protected mode of growth that allows the colonizing microbial cells to survive in hostile environments, even when an antimicrobial agent is present. The scientific community has ...come to understand many things about the growth dynamics and behavior of microbial biofilms. It is now accepted that biofilm formation is a multifactorial process that starts with the adhesion of individual cells and (auto-)coaggregates of cells to a surface. Then, attached cells grow, reproduce and secrete insoluble extracellular polymeric substances. As the biofilm matures, biofilm detachment and growth processes come into balance, such that the total amount of biomass on the surface remains approximately constant in time. The detached cells retain the phenotype of the biofilm cells, which facilitates the colonization of neighboring surfaces. The most common practice to eliminate unwanted biofilms is the application of antimicrobial agents. However, conventional antimicrobial agents often show inefficacy in the control of biofilms. Much remains to be understood in the biofilm formation process and in the development of effective strategies for biofilm prevention and control. The articles contained in this Special Issue deal with biofilms of some important bacteria (including pathogens such as
,
and
) and fungi (
), providing novel insights into their formation mechanisms and implications, together with novel methods (e.g., use of chemical conjugates and combinations of molecules) that can be used to disrupt the biofilm structure and kill the colonizing cells.
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