Phenotypic Traits and Immunomodulatory Properties of Leuconostoc carnosum Isolated From Meat Products

Twelve strains of Leuconostoc carnosum from meat products were investigated in terms of biochemical, physiological, and functional properties. The spectrum of sugars fermented by L. carnosum strains was limited to few mono- and disaccharides, consistently with the natural habitats of the species, including meat and fermented vegetables. The strains were able to grow from 4 to 37C with an optimum of approximately 32.5C. The ability to grow at temperatures compatible with refrigeration and in presence of up to 60 g/L NaCl explains the high loads of L. carnosum frequently described in many meat-based products. Six strains produced exopolysaccharides, causing a ropy phenotype of colonies, according to the potential involvement on L. carnosum in the appearance of slime in packed meat products. On the other side, the study provides evidence of a potential protective role of L. carnosum WC0321 and L. carnosum WC0323 against Listeria monocytogenes, consistently with the presence in these strains of the genes encoding leucocin B. Some meat-based products intended to be consumed without cooking may harbor up to 108 CFU/g of L. carnosum; therefore, we investigated the potential impact of this load on health. No strains survived the treatment with simulated gastric juice. Three selected strains were challenged for the capability to colonize a mouse model and their immunomodulatory properties were investigated. The strains did not colonize the intestine of mice during 10 days of daily dietary administration. Intriguingly, despite the loss of viability during the gastrointestinal transit, the strains exhibited different immunomodulatory effect on the maturation of dendritic cells in vivo, the extent of which correlated to the production of exopolysaccharides. The ability to stimulate the mucosal associated immune system in such probiotic-like manner, the general absence of antibiotic resistance genes, and the lack of the biosynthetic pathways for biogenic amines should reassure on the safety of this species, with potential for exploitation of selected starters

Antibiotic resistance, virulence factors, phenotyping, and genotyping of non\u2013escherichia coli enterobacterales from the gut microbiota of healthy subjects

Non-Escherichia coli Enterobacterales (NECE) can colonize the human gut and may present virulence determinants and phenotypes that represent severe heath concerns. Most information is available for virulent NECE strains, isolated from patients with an ongoing infection, while the commensal NECE population of healthy subjects is understudied. In this study, 32 NECE strains were isolated from the feces of 20 healthy adults. 16S rRNA gene sequencing and mass spectrometry attributed the isolates to Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, Enterobacter aerogenes, Enterobacter kobei, Citrobacter freundii, Citrobacter amalonaticus, Cronobacter sp., and Hafnia alvei, Morganella morganii, and Serratia liquefaciens. Multiplex PCR revealed that K. pneumoniae harbored virulence genes for adhesins (mrkD, ycfM, and kpn) and enterobactin (entB) and, in one case, also for yersiniabactin (ybtS, irp1, irp2, and fyuA). Virulence genes were less numerous in the other NECE species. Biofilm formation was spread across all the species, while curli and cellulose were mainly produced by Citrobacter and Enterobacter. Among the most common antibiotics, amoxicillin-clavulanic acid was the sole against which resistance was observed, only Klebsiella strains being susceptible. The NECE inhabiting the intestine of healthy subjects have traits that may pose a health threat, taking into account the possibility of horizontal gene transfer

Comparative Genomics of Leuconostoc carnosum

Leuconostoc carnosum is a known colonizer of meat-related food matrices. It reaches remarkably high loads during the shelf life in packaged meat products and plays a role in spoilage, although preservative effects have been proposed for some strains. In this study, the draft genomes of 17 strains of L. carnosum (i.e., all the strains that have been sequenced so far) were compared to decipher their metabolic and functional potential and to determine their role in food transformations. Genome comparison and pathway reconstruction indicated that L. carnosum is a compact group of closely related heterofermentative bacteria sharing most of the metabolic features. Adaptation to a nitrogen-rich environment, such as meat, is evidenced by 23 peptidase genes identified in the core genome and by the autotrophy for nitrogen compounds including several amino acids, vitamins, and cofactors. Genes encoding the decarboxylases yielding biogenic amines were not present. All the strains harbored 1–4 of 32 different plasmids, bearing functions associated to proteins hydrolysis, transport of amino acids and oligopeptides, exopolysaccharides, and various resistances (e.g., to environmental stresses, bacteriophages, and heavy metals). Functions associated to bacteriocin synthesis, secretion, and immunity were also found in plasmids. While genes for lactococcin were found in most plasmids, only three harbored the genes for leucocin B, a class IIa antilisterial bacteriocin. Determinants of antibiotic resistances were absent in both plasmids and chromosomes

Antibiotic Resistance, Virulence Factors, Phenotyping, and Genotyping of E. coli Isolated from the Feces of Healthy Subjects

Escherichia coli may innocuously colonize the intestine of healthy subjects or may instigate infections in the gut or in other districts. This study investigated intestinal E. coli isolated from 20 healthy adults. Fifty-one strains were genotyped by molecular fingerprinting and analyzed for genetic and phenotypic traits, encompassing the profile of antibiotic resistance, biofilm production, the presence of surface structures (such as curli and cellulose), and their performance as recipients in conjugation experiments. A phylogroup classification and analysis of 34 virulence determinants, together with genes associated to the pks island (polyketide-peptide genotoxin colibactin) and conjugative elements, was performed. Most of the strains belonged to the phylogroups B1 and B2. The different phylogroups were separated in a principal coordinate space, considering both genetic and functional features, but not considering pulsed-field gel electrophoresis. Within the B2 and F strains, 12 shared the pattern of virulence genes with potential uropathogens. Forty-nine strains were sensitive to all the tested antibiotics. Strains similar to the potential pathogens innocuously inhabited the gut of healthy subjects. However, they may potentially act as etiologic agents of extra-intestinal infections and are susceptible to a wide range of antibiotics. Nevertheless, there is still the possibility to control infections with antibiotic therapy

Development of osteoblast colonies on new bioactive coatings

The aging baby boomer population coupled with an increase in life expectancy is leading to a rising number of active elderly persons in occidental countries. As a result, the orthopedic implant industry is facing numerous challenges such as the need to extend implant life, reduce the incidence of revision surgery, and improve implant performance. This paper reports results of an investigation on the bioperformance of newly developed coating-substrate systems. Hydroxyapatite (HA) and nano-titania (nano-TiO\u2082) coatings were produced on Ti-6Al-4V and fiber reinforced polymer composite substrates. In vitro studies were conducted to determine the capacity of bioactive coatings developed to sustain osteoblast cells (fetal rat calvaria) adherence, growth, and differentiation. As revealed by scanning electron microscopy (SEM) observations and alkaline phosphatase activity, cell adhesion and proliferation demonstrated that HA coatings over a polymer composite are at least as good as HAcoatings made over Ti-6Al-4V substrate in terms of osteoblast cell activity. Nano-TiO\u2082 coatings produced by high-velocity oxyfuel (HVOF) spraying led to different results. For short-term cell culture (4.5 and 24 h), the osteoblasts appeared more flattened when grown on nano-TiO\u2082 than on HA. The surface cell coverage after seven days of incubation was also more complete on nano-TiO\u2082 than HA. Preliminary results indicate that osteoblast activity after 15 days of incubation on nano-TiO\u2082 is equivalent to or greater than that observed on HA.Peer reviewed: YesNRC publication: Ye

Stones and mortars protection: the new frontier of hybrid coatings

The environmental conditions can seriously affect the monumental stones and for this reason conservation of historical buildings is nowadays an important issue. Atmospheric pollution is the main responsible for stones deterioration and its impact on buildings has been studied in a systematic and scientific manner [Price, 1996]. Some of the major pollutants that seriously affect stoneworks are carbon, sulphur and nitrogen oxides together with aerosol particulate matter such as smoke, the main responsible of surface soiling. Lastly, the presence and movement of moisture within a material, facilitated by high porosity, can enhance and alter the concentration of weathering agents and aid their damaging activity. In the last few years, hybrid coatings based on the synergic interaction between nanomaterials (nano-oxides) and tradition hydrophobic resins have been applied for restoration and conservation of works of art. In this work a commercially available Si-based resins have been applied as protective agents on both stone materials (Carrara, Botticino, Candoglia marbles and Angera stone) and mortars made using both hydraulic binder NHL 3.5 and lime putty. Furthermore, since it is well known that the mix of resins with nanoparticles allowed to obtain complete buoyancy and self-cleaning properties, hybrid coatings containing home-made TiO2 nanoparticles mixed with the commercial silane polymers ware applied to the stones and mortars. The results concerning the physico-chemical characteristics of the bare stones compared with those of the treated samples will be presented and discussed. In order to evaluate the stability of the applied coatings towards degradation induced by solar radiation and interaction with the atmospheric pollution, accelerated ageing tests under UV irradiation and exposure to a typical polluted urban environment for some months (during the autumn-winter period) have been carried out. For this purpose the following analyses have been performed: contact angle measurements, SEM-EDS (Scanning Electron Microscopy with X-ray microanalysis), IC (Ion Chromatography), colorimetric tests by DRS (Diffuse Reflectance Spectroscopy) followed by CIELab elaboration, porosity measurements, water absorption by capillarity and water vapor permeability. Static contact angle (\u3b8) measurements on the stone surfaces were performed in order to know their wetting properties. The application of AlphaSI30 coating leads to hydrophobic materials (90\ub0 < theta < 100\ub0) [Fermo et al., 2013]. In order to improve the water repellence of the coatings, nanoparticles (TiO2) deposition techniques [Soliveri et al., 2012] was used to induce superhydrophobicity. In this latter case, due to the enhanced water repellency of the resin-TiO2 film, the water drops bounced and rolled off the treated layer: the images sequence in Figure 1, taken by rising very slowly the support up to the contact with the pendant drop, until the drop stuck onto the TiO2 hybrid surface, well evidences the superhydrophobic behaviour. In order to investigate the stability of the coatings, accelerated aging tests by UV irradiation were carried out. Colorimetric measurements (CIELab) were performed to verify the color modification (yellowing) of the protective film due to solar exposition