Lichenysin-like Polypeptide Production by Bacillus licheniformis B3-15 and Its Antiadhesive and Antibiofilm Properties

We report the ability of the crude biosurfactant (BS B3-15), produced by the marine, thermotolerant Bacillus licheniformis B3-15, to hinder the adhesion and biofilm formation of Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213 to polystyrene and human cells. First, we attempted to increase the BS yield, optimizing the culture conditions, and evaluated the surface-active properties of cell-free supernatants. Under phosphate deprivation (0.06 mM) and 5% saccharose, the yield of BS (1.5 g/L) increased by 37%, which could be explained by the earlier (12 h) increase in lchAA expression compared to the non-optimized condition (48 h). Without exerting any anti-bacterial activity, BS (300 µg/mL) prevented the adhesion of P. aeruginosa and S. aureus to polystyrene (47% and 36%, respectively) and disrupted the preformed biofilms, being more efficient against S. aureus (47%) than P. aeruginosa (26%). When added to human cells, the BS reduced the adhesion of P. aeruginosa and S. aureus (10× and 100,000× CFU/mL, respectively) without altering the epithelial cells' viability. As it is not cytotoxic, BS B3-15 could be useful to prevent or remove bacterial biofilms in several medical and non-medical applications.

Anti-Bacterial Adhesion on Abiotic and Biotic Surfaces of the Exopolysaccharide from the Marine Bacillus licheniformis B3-15

The eradication of bacterial biofilm represents a crucial strategy to prevent a clinical problem associated with microbial persistent infection. In this study we evaluated the ability of the exopolysaccharide (EPS) B3-15, produced by the marine Bacillus licheniformis B3-15, to prevent the adhesion and biofilm formation of Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213 on polystyrene and polyvinyl chloride surfaces. The EPS was added at different times (0, 2, 4 and 8 h), corresponding to the initial, reversible and irreversible attachment, and after the biofilm development (24 or 48 h). The EPS (300 µg/mL) impaired the initial phase, preventing bacterial adhesion even when added after 2 h of incubation, but had no effects on mature biofilms. Without exerting any antibiotic activity, the antibiofilm mechanisms of the EPS were related to the modification of the (i) abiotic surface properties, (ii) cell-surface charges and hydrophobicity, and iii) cell-to-cell aggregation. The addition of EPS downregulated the expression of genes (lecA and pslA of P. aeruginosa and clfA of S. aureus) involved in the bacterial adhesion. Moreover, the EPS reduced the adhesion of P. aeruginosa (five logs-scale) and S. aureus (one log) on human nasal epithelial cells. The EPS could represent a promising tool for the prevention of biofilm-related infections.

Antimicrobial, antiadhesive, and antibiofilm actions of rhamnolipids on ESKAPE pathogens

The aim of this study was to test the antimicrobial, antiadhesive, and antibiofilm activities of a rhamnolipid extracted from Pseudomonas aeruginosa UKMP14T previously isolated from oil-contaminated soil in Malaysia against ESKAPE (i.e. multidrug resistant) pathogens. Zones of inhibition in an agar well diffusion assay were observed at 50 µg mL-1 concentrations of rhamnolipid for all the ESKAPE bacteria. The MIC and MBC values ranged between 7.81-62.5 µg mL-1 and 31.25-1000 µg mL-1, respectively. Percent killing was recorded to be >90% except for Klebsiella pneumoniae (86.84%). Furthermore, antiadhesion studies showed that there was 76% hindrance in attachment of Enterococcus faecium and 91% in Acinetobacter baumannii at 4 × MIC. The highest inhibition in adhesion was found at 4 × MIC, which was 46% for Ac. baumannii and 62% for Enterococcus faecium. Finally, the antibiofilm capability of the rhamnolipid was determined, which ranged between 25%-76% in Ac. baumannii and 35%-88% in Enterococcus faecium. To the best of our knowledge, this is the first study to include research on antimicrobial, antiadhesive and antibiofilm activities of rhamnolipid from the local isolate Ps. aeruginosa UKMP14T against ESKAPE bacteria. Obtained results suggest that this rhamnolipid can be exploited commercially for the production of novel antibiotics.

An Antibacterial and Antiadhesion In Situ Forming Hydrogel with Sol-Spray System for Noncompressible Hemostasis

Noncompressible hemorrhage is a major cause of posttrauma death and occupies the leading position among potentially preventable trauma-associated deaths. Recently, multiple studies have shown that strongly adhesive materials can serve as hemostatic materials for noncompressible hemorrhage. However, the risk of severe tissue adhesion limits the use of adhesive hydrogels as hemostatic materials. Here, we report a promising material system comprising an injectable sol and liquid spray as a potential solution. Injectable sol is mainly composed of gelatin (GEL) and sodium alginate (SA), which possess hemostasis and adhesive properties. The liquid spray component, a mixture of tannic acid (TA) and calcium chloride (CaCl₂), rapidly forms an antibacterial, antiadhesive and smooth film structure upon contact with the sol. In vitro and in vivo experiments demonstrated the bioabsorbable, biocompatible, antibacterial, and antiadhesion properties of the in situ forming hydrogel with a sol-spray system. Importantly, the addition of tranexamic acid (TXA) enhanced hemostatic performance in noncompressible areas and in deep wound hemorrhage. Our study offers a new multifunctional hydrogel system to achieve noncompressible hemostasis.

In Love with Shaping You-Influential Factors on the Breast Milk Content of Human Milk Oligosaccharides and Their Decisive Roles for Neonatal Development

Human milk oligosaccharides (HMOs) are structurally versatile sugar molecules constituting the third major group of soluble components in human breast milk. Based on the disaccharide lactose, the mammary glands of future and lactating mothers produce a few hundreds of different HMOs implicating that their overall anabolism utilizes rather high amounts of energy. At first sight, it therefore seems contradictory that these sugars are indigestible for infants raising the question of why such an energy-intensive molecular class evolved. However, in-depth analysis of their molecular modes of action reveals that Mother Nature created HMOs for neonatal development, protection and promotion of health. This is not solely facilitated by HMOs in their indigestible form but also by catabolites that are generated by microbial metabolism in the neonatal gut additionally qualifying HMOs as natural prebiotics. This narrative review elucidates factors influencing the HMO composition as well as physiological roles of HMOs on their way through the infant body and within the gut, where a major portion of HMOs faces microbial catabolism. Concurrently, this work summarizes in vitro, preclinical and observational as well as interventional clinical studies that analyzed potential health effects that have been demonstrated by or were related to either human milk-derived or synthetic HMOs or HMO fractions.

Ice-Inspired Superlubricated Electrospun Nanofibrous Membrane for Preventing Tissue Adhesion

Inspired by the superlubricated surface (SLS) of ice, which consists of an ultrathin and contiguous layer of surface-bound water, we built a SLS on the polycaprolactone (PCL)/poly(2-methacryloxyethylphosphorylcholine) (PMPC) composite nanofibrous membrane via electrospinning under controlled relative humidity (RH). The zwitterionic PMPC on the nanofiber provided a surface layer of bound water, thus generating a hydration lubrication surface. Prepared under 20% RH, electrospun PCL/PMPC nanofibers reached a minimum coefficient of friction (COF) of about 0.12 when the weight ratio of PMPC to PCL was 0.1. At a higher RH, a SLS with an ultralow COF of less than 0.05 was formed on the composite nanofibers. The high stability of the SLS hydration layer on the engineered nanofibrous membrane effectively inhibited fibroblast adhesion and markedly reduced tissue adhesion during tendon repair in vivo. This work demonstrates the great potential of this ice-inspired SLS approach in tissue adhesion-prevention applications.

New Levan-Type Exopolysaccharide from Bacillus amyloliquefaciens as an Antiadhesive Agent against Enterotoxigenic Escherichia coli

A special levan-type exopolysaccharide (EPS) from Bacillus amyloliquefaciens JN4 with antiadhesive activity against enterotoxigenic Escherichia coli (ETEC) was purified and identified. Chemical analysis indicated that EPS-JN4 with a low molecular weight of 8 kDa is composed of fructose and glucose with a molar ratio of 46.1:1. Structural analysis clarified that EPS-JN4 contains a main chain of β-(2,6)-linked Fruf residues and intensive branches of a single 2-linked Fruf at every six residues. Furthermore, the superior antiadhesive activity of EPS-JN4 against ETEC showed its potential usage as an antiadhesive agent for diarrhea prevention. EPS-JN4 is a specific type of levan family, for its small molecular size and intensive branches. The results expand the knowledge on structural types of levan and illustrate its potential as an antiadhesive agent for diarrhea prevention, which will be conducive to elucidate the relation between structure and function.

Interactions between Lubricin and Hyaluronic Acid Synergistically Enhance Antiadhesive Properties

Preventing the unwanted adsorption of proteins and cells at articular cartilage surfaces plays a critical role in maintaining healthy joints and avoiding degenerative diseases such as osteoarthritis. Immobilized at the surface of healthy articular cartilage is a thin, interfacial layer of macromolecules consisting mainly of hyaluronic acid (HA) and lubricin (LUB; a.k.a. PRG4) that is believed to form a co-adsorbed, composite film now known to exhibit synergistic tribological properties. Bioinspired by the composition of cartilage surfaces, composite layers of HA and LUB were grafted to Au surfaces and the antiadhesive properties were assessed using surface plasmon resonance and quartz crystal microbalance. A clear synergistic enhancement in antiadhesive properties was observed in the composite films relative to grafted HA and LUB layers alone. Atomic force microscopy (AFM) normal force measurements provide insight into the architecture of the HA/LUB composite layer and implicate a strong contribution of hydrophobic interactions in the binding of LUB end-domains directly to HA chains. These AFM force measurements indicate that the adhesion of LUB to HA is strong and indicate that the hydrophobic coupling of LUB to HA shields the hydrophobic domains in these molecules from interactions with other proteins or molecules.

Anti-adhesive activity of Aframomum melegueta major phenolics on lower respiratory tract pathogens

Recent studies have raised interest in the potential health effect of Aframomum melegueta, which is related to the phenolic content of its seeds. The methanolic extract of A. melegueta seeds showed a significant anti-adhesive effect against Staphylococcus aureus to lung carcinoma cell line in a concentration-dependent manner. The n-butanol and the chloroform fractions exhibited a significant antiadhesive activity against S. aureus. The chloroform fraction exhibited an antiadhesive effect of 49.53%, 40.15% and 70.34% at concentrations 25, 50 and 100 µg/mL, respectively. Through a biologically guided isolation, the chloroform fraction yielded a new diarylheptanoid identified using 1D, 2D NMR and HREIMS and named 3-(S)-acetyl-1-(4',5'-dihydroxy-3'- methoxyphenyl)-7-(3″,4″-dihydroxyphenyl)heptane(1), in addition to eight known compounds (2-9). Compounds (1), 6-paradol (5), [6]-shogaol (7), [8]-gingerol(8) and dihydro[6]paradol (9) exhibited a significant anti-adhesive activity against S. aureus with a % of inhibition of adhesion of 60.58, 50, 70.07, 85.4, 59.85% at 50 µg/mL, respectively. Additionally, the extract's capacity to reduce adhesion without reducing bacterial growth reduces the likeliness of resistance development.

Food-Safe Modification of Stainless Steel Food-Processing Surfaces to Reduce Bacterial Biofilms

Biofilm formation on stainless steel (SS) surfaces of food-processing plants, leading to food-borne illness outbreaks, is enabled by the attachment and confinement of pathogens within microscale cavities of surface roughness (grooves, scratches). We report foodsafe oil-based slippery coatings (FOSCs) for food-processing surfaces that suppress bacterial adherence and biofilm formation by trapping residual oil lubricant within these surface cavities to block microbial growth. SS surfaces were chemically functionalized with alkylphosphonic acid to preferentially wet a layer of food-grade oil. FOSCs reduced the effective surface roughness, the adhesion of organic food residue, and bacteria. FOSCs significantly reduced Pseudomonas aeruginosa biofilm formation on standard roughness SS-316 by 5 log CFU cm^-2, and by 3 log CFU cm^-2 for mirror-finished SS. FOSCs also enhanced surface cleanability, which we measured by bacterial counts after conventional detergent cleaning. Importantly, both SS grades maintained their antibiofilm activity after the erosion of the oil layer by surface wear with glass beads, which suggests that there is a residual volume of oil that remains to block surface cavity defects. These results indicate the potential of such low-cost, scalable approaches to enhance the cleanability of SS food-processing surfaces and improve food safety by reducing biofilm growth.

Carbohydrate-Lectin Interactions: An Unexpected Contribution to Affinity

Uropathogenic E. coli exploit PapG-II adhesin for infecting host cells of the kidney; the expression of PapG-II at the tip of bacterial pili correlates with the onset of pyelonephritis in humans, a potentially life-threatening condition. It was envisaged that blocking PapG-II (and thus bacterial adhesion) would provide a viable therapeutic alternative to conventional antibiotic treatment. In our search for potent PapG-II antagonists, we observed an increase in affinity when tetrasaccharide 1, the natural ligand of PapG-II in human kidneys, was elongated to hexasaccharide 2, even though the additional Siaα(2-3)Gal extension is not in direct contact with the lectin. ITC studies suggest that the increased affinity results from partial desolvation of nonbinding regions of the hexasaccharide; this is ultimately responsible for perturbation of the outer hydration layers. Our results are in agreement with previous observations and suggest a general mechanism for modulating carbohydrate-protein interactions based on nonbinding regions of the ligand.

Lubricin as a novel nanostructured protein coating to reduce fibroblast density

Excessive fibroblast adhesion and proliferation on the surface of medical implants (such as catheters, endotracheal tubes, intraocular lenses, etc) can lead to major postsurgical complications. This study showed that when coated on tissue culture polystyrene, lubricin, a nanostructured mucinous glycoprotein found in the synovial fluid of joints, decreased fibroblast density for up to 2 days of culture compared to controls treated with phosphate buffered saline (PBS). When examining why, similar antifibroblast density results were found when coating tissue culture polystyrene with bovine submaxillary mucin (BSM), an even smaller protein closely related to the central subregion of lubricin. Additionally, results from this study demonstrated that in contrast to BSM or controls (PBS-coated and non-coated samples), lubricin was better at preserving the health of nonadherent or loosely adherent fibroblasts; fibroblasts that did not adhere or loosely adhered on the lubricin-coated tissue culture polystyrene adhered and proliferated well for up to an additional day when they were reseeded on uncoated tissue culture polystyrene. In summary, this study provides evidence for the promise of nanostructured lubricin (and to a lesser extent BSM) to inhibit fibroblast adhesion and growth when coated on medical devices; lubricin should be further explored for numerous medical device applications.

The functional paradox of CD43 in leukocyte recruitment: a study using CD43-deficient mice

Although there is considerable evidence implicating a role for CD43 (leukosialin) in leukocyte cell-cell interactions, its precise function remains uncertain. Using CD43-deficient mice (CD43(-/-)) and intravital microscopy to directly visualize leukocyte interactions in vivo, we investigated the role of CD43 in leukocyte-endothelial cell interactions within the cremasteric microcirculation under flow conditions. Our studies demonstrated significantly enhanced leukocyte rolling and adhesion after chemotactic stimuli in CD43(-/-) mice compared with wild type mice. Using an in vitro flow chamber, we established that the enhanced rolling interactions of CD43(-/-) leukocytes, primarily neutrophils, were also observed using immobilized E-selectin as a substrate, suggesting that passive processes related to steric hindrance or charge repulsion were likely mechanisms. Despite increased adhesion and rolling interactions by CD43(-/-) leukocytes, we uncovered a previously unrecognized impairment of CD43(-/-) leukocytes to infiltrate tissues. Oyster glycogen-induced neutrophil and monocyte infiltration into the peritoneum was significantly reduced in CD43(-/-) mice. In response to platelet activating factor, CD43(-/-) leukocytes were impaired in their ability to emigrate out of the vasculature. These results suggest that leukocyte CD43 has a dual function in leukocyte-endothelial interactions. In addition to its role as a passive nonspecific functional barrier, CD43 also facilitates emigration of leukocytes into tissues.