Histological assessment, anti-quorum sensing, and anti-biofilm activities of Dioon spinulosum extract: in vitro and in vivo approach

Pseudomonas aeruginosa is an opportunistic bacterium causing several health problems and having many virulence factors like biofilm formation on different surfaces. There is a significant need to develop new antimicrobials due to the spreading resistance to the commonly used antibiotics, partly attributed to biofilm formation. Consequently, this study aimed to investigate the anti-biofilm and anti-quorum sensing activities of Dioon spinulosum, Dyer Ex Eichler extract (DSE), against Pseudomonas aeruginosa clinical isolates. DSE exhibited a reduction in the biofilm formation by P. aeruginosa isolates both in vitro and in vivo rat models. It also resulted in a decrease in cell surface hydrophobicity and exopolysaccharide quantity of P. aeruginosa isolates. Both bright field and scanning electron microscopes provided evidence for the inhibiting ability of DSE on biofilm formation. Moreover, it reduced violacein production by Chromobacterium violaceum (ATCC 12,472). It decreased the relative expression of 4 quorum sensing genes (lasI, lasR, rhlI, rhlR) and the biofilm gene (ndvB) using qRT-PCR. Furthermore, DSE presented a cytotoxic activity with IC50 of 4.36 ± 0.52 µg/ml against human skin fibroblast cell lines. For the first time, this study reports that DSE is a promising resource of anti-biofilm and anti-quorum sensing agents.

Control of Multidrug-Resistant Pathogenic Staphylococci Associated with Vaginal Infection Using Biosurfactants Derived from Potential Probiotic Bacillus Strain

Biosurfactants exhibit antioxidant, antibacterial, antifungal, and antiviral activities. They can be used as therapeutic agents and in the fight against infectious diseases. Moreover, the anti-adhesive properties against several pathogens point to the possibility that they might serve as an anti-adhesive coating agent for medical inserts and prevent nosocomial infections, without using synthetic substances. In this study, the antimicrobial, antibiofilm, cell surface hydrophobicity, and antioxidative activities of biosurfactant extracted from Bacillus sp., against four pathogenic strains of Staphylococcus spp. associated with vaginal infection, were studied. Our results have shown that the tested biosurfactant possesses a promising antioxidant potential, and an antibacterial potency against multidrug clinical isolates of Staphylococcus, with an inhibitory diameter ranging between 27 and 37 mm, and a bacterial growth inhibition at an MIC of 1 mg/ mL, obtained. The BioSa3 was highly effective on the biofilm formation of different tested pathogenic strains. Following their treatment by BioSa3, a significant decrease in bacterial attachment (p < 0.05) was justified by the reduction in the optical (from 0.709 to 0.111) following their treatment by BioSa3. The antibiofilm effect can be attributed to its ability to alter the membrane physiology of the tested pathogens to cause a significant decrease (p < 0.05) of over 50% of the surface hydrophobicity. Based on the obtained result of the bioactivities in the current study, BioSa3 is a good candidate in new therapeutics to better control multidrug-resistant bacteria and overcome bacterial biofilm-associated infections by protecting surfaces from microbial contamination.

Isolation and probiotic potential of lactic acid bacteria from swine feces for feed additive composition

Animal microbiota is becoming an object of interest as a source of beneficial bacteria for commercial use. Moreover, the escalating problem of bacterial resistance to antibiotics is threatening animals and humans; therefore, in the last decade intensive search for alternative antimicrobials has been observed. In this study, lactic acid bacteria (LAB) were isolated from suckling and weaned pigs feces (376) and characterized to determine their functional properties and usability as pigs additives. Selection of the most promising LAB was made after each stage of research. Isolates were tested for their antimicrobial activity (376) and susceptibility to antibiotics (71). Selected LAB isolates (41) were tested for the production of organic acids, enzymatic activity, cell surface hydrophobicity and survival in gastrointestinal tract. Isolates selected for feed additive (5) were identified by MALDI-TOF mass spectrometry and partial sequence analysis of 16S rRNA gene, represented by Lentilactobacillus, Lacticaseibacillus (both previously classified as Lactobacillus) and Pediococcus genus. Feed additive prototype demonstrated high viability after lyophilization and during storage at 4 °C and − 20 °C for 30 days. Finally, feed additive was tested for survival in simulated alimentary tract of pigs, showing viability at the sufficient level to colonize the host. Studies are focused on obtaining beneficial strains of LAB with probiotic properties for pigs feed additive.

Autoinducer Analogs Can Provide Bactericidal Activity to Macrolides in Pseudomonas aeruginosa through Antibiotic Tolerance Reduction

Macrolide antibiotics are used in treating Pseudomonas aeruginosa chronic biofilm infections despite their unsatisfactory antibacterial activity, because they display several special activities, such as modulation of the bacterial quorum sensing and immunomodulatory effects on the host. In this study, we investigated the effects of the newly synthesized P. aeruginosa quorum-sensing autoinducer analogs (AIA-1, -2) on the activity of azithromycin and clarithromycin against P. aeruginosa. In the killing assay of planktonic cells, AIA-1 and -2 enhanced the bactericidal ability of macrolides against P. aeruginosa PAO1; however, they did not affect the minimum inhibitory concentrations of macrolides. In addition, AIA-1 and -2 considerably improved the killing activity of azithromycin and clarithromycin in biofilm cells. The results indicated that AIA-1 and -2 could affect antibiotic tolerance. Moreover, the results of hydrocarbon adherence and cell membrane permeability assays suggested that AIA-1 and -2 changed bacterial cell surface hydrophobicity and accelerated the outer membrane permeability of the hydrophobic antibiotics such as azithromycin and clarithromycin. Our study demonstrated that the new combination therapy of macrolides and AIA-1 and -2 may improve the therapeutic efficacy of macrolides in the treatment of chronic P. aeruginosa biofilm infections.

Inhibitory Effects of Cinnamaldehyde Derivatives on Biofilm Formation and Virulence Factors in Vibrio Species

Vibrio parahaemolyticus is considered one of the most relevant pathogenic marine bacteria with a range of virulence factors to establish food-related gastrointestinal infections in humans. Cinnamaldehyde (CNMA) and some of its derivatives have antimicrobial and antivirulence activities against several bacterial pathogens. This study examined the inhibitory effects of CNMA and its derivatives on biofilm formation and the virulence factors in Vibrio species, particularly V. parahaemolyticus. CNMA and ten of its derivatives were initially screened against V. parahaemolyticus biofilm formation, and their effects on the production of virulence factors and gene expression were studied. Among the CNMA derivatives tested, 4-nitrocinnamaldehyde, 4-chlorocinnamaldehyde, and 4-bromocinnamaldehyde displayed antibacterial and antivirulence activities, while the backbone CNMA had weak effects. The derivatives could prevent the adhesion of V. parahaemolyticus to surfaces by the dose-dependent inhibition of cell surface hydrophobicity, fimbriae production, and flagella-mediated swimming and swarming phenotypes. They also decreased the protease secretion required for virulence and indole production, which could act as an important signal molecule. The expression of QS and biofilm-related genes (aphA, cpsA, luxS, and opaR), virulence genes (fliA, tdh, and vopS), and membrane integrity genes (fadL, and nusA) were downregulated in V. parahaemolyticus by these three CNMA analogs. Interestingly, they eliminated V. parahaemolyticus and reduced the background flora from the squid surface. In addition, they exhibited similar antimicrobial and antibiofilm activities against Vibrio harveyi. This study identified CNMA derivatives as potential broad-spectrum antimicrobial agents to treat biofilm-mediated Vibrio infections and for surface disinfection in food processing facilities.

Evaluation of cell surface hydrophobicity and biofilm formation as pathogenic determinants among ESBL producing uropathogenic Escherichia coli

The attachment of the bacteria to the host cell and ability to invade the cell are regarded as important steps in the infectious process. The hydrophobicity of the microbial surface plays a critical role in the adherence of bacteria to the surface. The ability of biofilm formation can increase survival chance of microorganism, as cell growing in biofilm are highly resistant to the components of the immune system and many antimicrobial agents. Infection caused by ESBL- producers are associated with severe adverse outcomes and may be related to increased virulence of these strains.: A total of 100 urinary were selected for the study, of which 50 strains were from ESBL producers and 50 from non- ESBL-producing uropathogenic(UPEC) strains. The urinary isolates that were resistant to at least one of the three indicator cephalosporins (cefotaxime, cefpodoxime and ceftazidime) were tested for ESBL production by quantitative E-strip method. All the 100 urinary strains were tested for cell surface hydrophobicity (CSH) by salt aggregation method and Biofilm production by tissue culture plate method.Among ESBL producers, 19 (38%) were CSH positive and 34 (68%) were biofilm producers. However among non-ESBL producers, 05 (10%) were CSH positive and 12 (24%) were biofilm producers. Statistically significant difference (&#60;0.001) was seen in the occurrence of CSH and biofilm production between ESBL and non ESBL producing UPEC isolates.In the present study, it was found that the ESBL producing isolates had a higher ability to form biofilm and CSH; both of them are among the important virulence factors associated with cell surface adherence which is the first step in bacterial infection.

In vitro biodegradation of low-density polyethylene by soil microorganisms

The accumulation of recalcitrant plastics in the environment, particularly polyethylene, is a major threat to the ecology. Among the different kinds of polyethylene, low-density polyethylene (LDPE) is the most widely used polyethylene. The goal of this work was to isolate and discover a powerful polyethylene degrading microbial strain from plastic waste disposal soil. The bacterial and fungal strains were isolated by enrichment technique and were identified based on the morphological and biochemical characteristics. Further, they were screened individually for their lowdensity polyethylene (LDPE) degrading efficiency by in vitro biodegradation assay. The efficiency of the potent strain to colonize on the LDPE surface and its biodegradation ability were investigated. The degraded products of low-density polyethylene were analysed by FTIR after the biodegradation study which was conducted for a long incubation period by inoculating the selected bacterial strain in synthetic medium (SM) with LDPE as the carbon source. Totally six different bacterial and five different fungal strains were isolated from the polluted soil. Among the bacterial strains, the JSB2, JSB3 and JSB4 and among the fungal strains, JSF1, JSF3 and JSF4 showed maximum growth, more cell surface hydrophobicity and weight loss and they were selected for further studies. The incubation of LDPE films with bacteria and fungi led to the formation of new absorbance bands such as dehydrated dimer of carbonyl group (1720 cm-1), CH3 deformation (1463 cm-1) and C=C conjugation band (862 cm-1). The results inferred that the exogenous addition of these microbes to LDPE contaminated soil causes an enhanced degradation. Among the microbial isolates, Bacillus species showed high degradation.

Evaluation of the Adhesive Potential of Bacteria Isolated from Meat-Related Sources

Microbial adhesion constitutes the transition of microorganisms from a planktonic mode to a static one. It promotes the formation of biofilm which is responsible for spoilage, foodborne diseases, and corrosion in the food processing industry. In this study, the adhesive potential of fourteen meat-borne bacterial isolates belonging to seven different genera was investigated. All strains were found able to colonize polystyrene surfaces with different levels of firmness. Significant variations were determined in assays of bacterial hydrophobicity and motility. Among the 14 strains, Pseudomonas fragi, Aeromonas salmonicida II, Serratia liquefaciens, Citrobacter braakii, Pseudomonas putida, and Aeromonas veronii had a strong hydrophobic force, while the isolates of Lactobacillus genus showed the most hydrophilic property. In terms of motility, Citrobacter braakii and Escherichia coli exhibited exceptional swarming and swimming abilities, whilst conservatively weak performances were observed in the Lactobacillus strains. Furthermore, the majority of the isolates were predominantly electron donors and weak electron acceptors. Overall, a high level of correlation was observed between biofilm-forming ability with cell surface hydrophobicity and Lewis acid–base properties, whereas the contribution of motility in bacterial adhesion could not be confirmed. Research on the adhesive performance of foodborne bacteria is potentially conducive to developing novel control strategies, such as food processing equipment with specific surfaces, not facilitating attachment.

Thioredoxin-mediated alteration of protein content and cytotoxicity of Acinetobacter baumannii outer membrane vesicles

Acinetobacter baumannii is a Gram-negative bacterium responsible for many hospital-acquired infections including ventilator-associated pneumonia and sepsis. We have previously identified A. baumannii thioredoxin A protein (TrxA) as a virulence factor with a multitude of functions including reduction of protein disulfides. TrxA plays an important role in resistance to oxidative stress facilitating host immune evasion in part by alteration of type IV pili and cell surface hydrophobicity. Other virulence factors such as outer membrane vesicles (OMV) shed by bacteria have been shown to mediate bacterial intercellular communication and modulate host immune response. To investigate whether OMVs can be modulated by TrxA, we isolated OMVs from wild type (WT) and TrxA-deficient (ΔtrxA) A. baumannii clinical isolate Ci79 and carried out a functional and proteomic comparison. Despite attenuation of ΔtrxA in a mouse challenge model, pulmonary inoculation of ΔtrxA OMVs resulted in increased lung permeability compared to WT OMVs. Furthermore, ΔtrxA OMVs induced more J774 macrophage-like cell death than WT OMVs. This ΔtrxA OMV-mediated cell death was abrogated when cells were incubated with protease-K-treated OMVs suggesting OMV proteins were responsible for cytotoxicity. We therefore compared WT and mutant OMV proteins using proteomic analysis. We observed that up-regulated and unique ΔtrxA OMV proteins consisted of many membrane bound proteins involved in small molecule transport as well as proteolytic activity. Bacterial OmpA, metalloprotease, and fimbrial protein have been shown to enhance mammalian cell apoptosis through various mechanisms. Differential packaging of these proteins in ΔtrxA OMVs may contribute to the increased cytotoxicity observed in this study.