In vitro resistance and evolution of resistance to tavaborole in Trichophyton rubrum

Tavaborole is currently used in the topical treatment of onychomycosis. In this study, we analyzed the in vitro emergence/evolution of resistance against tavaborole in Trichophyton rubrum When T. rubrum strains were propagated on media containing the MIC of tavaborole, spontaneous resistant mutants were isolated at a frequency of 10-8 The frequency was almost 100-fold higher following fungal growth in the presence of a sub-inhibitory tavaborole concentration (0.5-fold the MIC) for ten transfers. All collected mutants showed similar 4- to 8-fold increase in the drug minimal inhibitory concentration. No cross-resistance to other antifungals was evidenced

In vitro assessment of probiotic attributes for strains contained in commercial formulations

Although probiotics are often indiscriminately prescribed, they are not equal and their effects on the host may profoundly differ. In vitro determination of the attributes of probiotics should be a primary concern and be performed even before clinical studies are designed. In fact, knowledge on the biological properties a microbe possesses is crucial for selecting the most suitable bacteriotherapy for each individual. Herein, nine strains (Bacillus clausii NR, OC, SIN, T, Bacillus coagulans ATCC 7050, Bifidobacterium breve DSM 16604, Limosilactobacillus reuteri DSM 17938, Lacticaseibacillus rhamnosus ATCC 53103, and Saccharomyces boulardii CNCM I-745) declared to be contained in six commercial formulations were tested for their ability to tolerate simulated intestinal conditions, adhere to mucins, and produce β-galactosidase, antioxidant enzymes, riboflavin, and D-lactate. With the exception of B. breve, all microbes survived in simulated intestinal fluid. L. rhamnosus was unable to adhere to mucins and differences in mucin adhesion were evidenced for L. reuteri and S. boulardii depending on oxygen levels. All microorganisms produced antioxidant enzymes, but only B. clausii, B. coagulans, B. breve, and L. reuteri synthesize β-galactosidase. Riboflavin secretion was observed for Bacillus species and L. rhamnosus, while D-lactate production was restricted to L. reuteri and L. rhamnosus. Our findings indicate that the analyzed strains possess different in vitro biological properties, thus highlighting the usefulness of in vitro tests as prelude for clinical research

Bacillus cereus in Dairy Products and Production Plants

Spore-forming Bacillus cereus is a common contaminant of dairy products. As the microorganism is widespread in the environment, it can contaminate milk at the time of milking, but it can also reach the dairy products in each phase of production, storage and ripening. Milk pasteurization treatment is not effective in reducing contamination and can instead act as an activator of spore germination, and a potential associated risk still exists with the consumption of some processed foods. Prevalences and concentrations of B. cereus in milk and dairy products are extremely variable worldwide: in pasteurized milk, prevalences from 2% to 65.3% were reported, with concentrations of up to 3 × 105 cfu/g, whereas prevalences in cheeses ranged from 0 to 95%, with concentrations of up to 4.2 × 106 cfu/g. Bacillus cereus is also well known to produce biofilms, a serious concern for the dairy industry, with up to 90% of spores that are resistant to cleaning and are easily transferred. As the contamination of raw materials is not completely avoidable, and the application of decontamination treatments is only possible for some ingredients and is limited by both commercial and regulatory reasons, it is clear that the correct application of hygienic procedures is extremely important in order to avoid and manage the circulation of B. cereus along the dairy supply chain. Future developments in interventions must consider the synergic application of different mild technologies to prevent biofilm formation and to remove or inactivate the microorganism on the equipment

Antimicrobial Activity of Xibornol and a Xibornol-Based Formulation Against Gram-Positive Pathogens of the Respiratory Tract

: Xibornol is known since the 70s and a xibornol-based formulation is commercialized as spray suspension for the antisepsis of the oral cavity and as adjuvant in pharyngeal infections caused by Gram-positive microorganisms. Herein, we evaluated the antimicrobial activity of xibornol and the xibornol-based formulation against common pathogens of the upper and lower respiratory tract.Our results indicate that xibornol alone and the xibornol-based formulation have strong antibacterial action against Streptococcus pneumoniae, Streptococcus pyogenes, and Staphyloccus aureus, as well as against the two emerging pathogens Actinomyces israelii and Corynebacterium ulcerans. These findings highlight the antimicrobial potential of these drugs in the topical control of pathogenic Gram-positive bacteria of the respiratory tract

FlhF Is Required for Swarming Motility and Full Pathogenicity of Bacillus cereus

Besides sporulation, Bacillus cereus can undergo a differentiation process in which short swimmer cells become elongated and hyperflagellated swarmer cells that favor migration of the bacterial community on a surface. The functionally enigmatic flagellar protein FlhF, which is the third paralog of the signal recognition particle (SRP) GTPases Ffh and FtsY, is required for swarming in many bacteria. Previous data showed that FlhF is involved in the control of the number and positioning of flagella in B. cereus. In this study, in silico analysis of B. cereus FlhF revealed that this protein presents conserved domains that are typical of SRPs in many organisms and a peculiar N-terminal basic domain. By proteomic analysis, a significant effect of FlhF depletion on the amount of secreted proteins was found with some proteins increased (e.g., B component of the non-hemolytic enterotoxin, cereolysin O, enolase) and others reduced (e.g., flagellin, L2 component of hemolysin BL, bacillolysin, sphingomyelinase, PC-PLC, PI-PLC, cytotoxin K) in the extracellular proteome of a ΔflhF mutant. Deprivation of FlhF also resulted in significant attenuation in the pathogenicity of this strain in an experimental model of infection in Galleria mellonella larvae. Our work highlights the multifunctional role of FlhF in B. cereus, being this protein involved in bacterial flagellation, swarming, protein secretion, and pathogenicity

Delivery Mode Shapes the Composition of the Lower Airways Microbiota in Newborns

Radical alterations in the human microbiota composition are well-known to be associated with many pathological conditions. If these aberrations are established at the time of birth, the risk of developing correlated pathologies throughout life is significantly increased. For this reason, all newborns should begin their lives with a proper microbiota in each body district. The present study aimed at demonstrating a correlation between the mode of delivery and the development of a well-balanced microbiota in the lower airways of newborns. 44 pregnant women were enrolled in this study. Microbiological comparative analysis was carried out on tracheobronchial secretions of babies born through vaginal delivery (VD) or caesarean section (CS). All samples showed the presence of bacterial DNA, regardless of the mode of delivery. No viable cultivable bacteria were isolated from the CS samples. On the contrary, VD allowed colonization of the lower airways by alive cultivable bacteria. The identification of bacterial species revealed that Lactobacillus spp. and Bacteroides vulgatus were the most common microorganisms in the lower airways of vaginally-delivered newborns. Data obtained from quantitative PCRs showed a significantly higher total bacterial load, as well as Firmicutes and Lactobacillus spp. amount, in VD samples than CS ones, while no statistically significant difference was found in Torque Teno Virus (TTV) load between samples. Taken together, our findings confirm the hypothesis that passage through the maternal vaginal canal determines more beneficial colonization of the lower airways in newborns

Study of the Adhesion of the Human Gut Microbiota on Electrospun Structures

Although the adhesion of bacteria on surfaces is a widely studied process, to date, most of the works focus on a single species of microorganisms and are aimed at evaluating the antimicrobial properties of biomaterials. Here, we describe how a complex microbial community, i.e., the human gut microbiota, adheres to a surface to form stable biofilms. Two electrospun structures made of natural, i.e., gelatin, and synthetic, i.e., polycaprolactone, polymers were used to study their ability to both promote the adhesion of the human gut microbiota and support microbial growth in vitro. Due to the different wettabilities of the two surfaces, a mucin coating was also added to the structures to decouple the effect of bulk and surface properties on microbial adhesion. The developed biofilm was quantified and monitored using live/dead imaging and scanning electron microscopy. The results indicated that the electrospun gelatin structure without the mucin coating was the optimal choice for developing a 3D in vitro model of the human gut microbiota

The administration of Enterococcus faecium SF68 counteracts compositional shifts in the gut microbiota of diet-induced obese mice

Microorganisms with probiotic properties are eliciting an increasing interest as coadjuvants in the prevention and treatment of obesity through modulation of the gut microbiota. In this study, a probiotic formulation based on Enterococcus faecium SF68 was administered to mice fed with a high-fat diet (HFD) to evaluate its efficacy in reducing body mass gain and in modulating the intestinal bacterial composition. Both stool and ileum samples were collected from untreated and treated mice and absolute abundances of specific taxa constituting the gut microbial consortium were evaluated. SF68 administration significantly reduced the HFD-induced weight gain. In these animals, the microbial gut composition shifted toward an enrichment in microbes positively correlated with mucus thickness, lower inflammation, lower glycemia levels, and SCFA production (i.e., Bifidobacterium, Akkermansia, and Faecalibacterium), as well as a depletion in bacterial phyla having a key role in obesity (i.e., Firmicutes, Proteobacteria). Our results demonstrate the efficacy of E. faecium SF68 in adjusting the composition of the dysbiotic microbiota of HFD-fed animals, thus ameliorating clinical conditions and exerting anti-obesity effects

The genus Bacillus: from pathogens to beneficial microbes

The genus Bacillus is a phenotypically large, heterogeneous collection of spore-forming Gram-positive rods that can be isolated from a great variety of environments. With the exception of B. anthracis and B. cereus, the large majority of these bacteria display poor pathogenicity in humans and are most often considered as contaminants in clinical practice. Nevertheless, occasional infections due to other Bacillus species have been reported in recent years. B. cereus mainly causes food-poisoning diseases, but it is also increasingly associated with serious human local and systemic infections. The pathogenic potential of B. cereus is due to the secretion of virulence proteins and to the presence of flagella, which play a crucial role in bacterial adhesion to surfaces and in swimming and swarming motility. The signal recognition particle (SRP)-GTPase FlhF has been shown to regulate protein secretion, flagellar formation, and flagellum-dependent motility modes in B. cereus, thus suggesting its key role in B. cereus pathogenicity. For their wide range of physiological characteristics and ability to produce a multitude of enzymes, antibiotics, and metabolites, Bacillus species are used in many medical, pharmaceutical, agricultural, and industrial processes. Bacillus spores, particularly those of the GRAS (generally recognized as safe) species B. clausii and B. coagulans, have a long history of consumption and safe use as probiotics, live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. Probiotic products containing spores for human or animal use are commercialized in several countries, being widespread in Australia, Europe, Asia, USA, and South America. Chapter 1 is a general introduction to the genus Bacillus, B. cereus and its virulence, and to the role of FlhF in the regulation of flagella and virulence. The application of Bacillus strains as probiotics is also introduced. In chapter 2, we evaluated the prevalence of Bacillus spp. in clinical cultures and the application of matrix-assisted laser desorption-ionization time of flight mass spectrometry (MALDI-TOF MS) as a diagnostic technique for the identification of these bacteria. Antibiotic susceptibility and virulence potential of the clinical isolates are also reported. In chapter 3, the effects of FlhF depletion on swarming, protein secretion and pathogenicity of B. cereus are analyzed. In chapter 4, we gained more insight on the role of FlhF as SRP-GTPase in B. cereus. In particular, the ability of FlhF to self-dimerize and interact with the L2 component of the toxin hemolysin BL are reported. In chapter 5, the compositional quality and potential gastrointestinal behavior of three Bacillus-based probiotic formulations was analyzed in comparison with other top formulations commercialized in Italy. Acid resistance and bile tolerance were investigated. Chapter 6 includes a general, updated discussion and the conclusions on the overall results