Real-Time Antimicrobial Susceptibility Assay of Planktonic and Biofilm Bacteria by Isothermal Microcalorimetry.

Most antimicrobials currently used in the clinical practice are tested as growth inhibitors against free-floating microorganisms in a liquid suspension, rather than against sessile cells constituting biofilms. Hence, reliable, fast, and reproducible methods for assessing biofilm susceptibility to antimicrobials are strongly needed. Isothermal microcalorimetry (IMC) is a nondestructive sensitive technique that allows for the real-time monitoring of microbial viability in the presence or absence of antimicrobial compounds. Therefore, the efficacy of specific antimicrobials, alone or in combination, may be promptly validated supporting the development of new drugs and avoiding the administration of ineffective therapies. Furthermore, the susceptibility of both planktonic and biofilm cells to antimicrobials can be conveniently assessed without the need for elaborated staining procedures and under nontoxic working conditions. Quantitative data regarding the antimicrobial effect against different strains might be collected by monitoring the microbial cell replication, and, more importantly, a dose-dependent activity can be efficiently detected by measuring the delay and decrease in the heat flow peak of the treated samples. A limitation of IMC for anti-biofilm susceptibility test is the inability to directly quantify the non-replicating cells in the biofilm or the total biomass. However, as IMC is a nondestructive method, the samples can be also analyzed by using different techniques, acquiring more information complementary to calorimetric data. IMC finds application also for the investigation of antibiotic eluting kinetics from different biomaterials, as well as for studying bacteriophages activity against planktonic and biofilm bacteria. Thus, the wide applicability of this ultra-sensitive and automated technique provides a further advance in the field of clinical microbiology and biomedical sciences.

Pre-diagnostic copper and zinc biomarkers and colorectal cancer risk in the European Prospective Investigation into Cancer and Nutrition cohort.

Adequate intake of copper and zinc, two essential micronutrients, are important for antioxidant functions. Their imbalance may have implications for development of diseases like colorectal cancer (CRC), where oxidative stress is thought to be etiologically involved. As evidence from prospective epidemiologic studies is lacking, we conducted a case-control study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort to investigate the association between circulating levels of copper and zinc, and their calculated ratio, with risk of CRC development. Copper and zinc levels were measured by reflection X-ray fluorescence spectrometer in 966 cases and 966 matched controls. Multivariable adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated using conditional logistic regression and are presented for the fifth versus first quintile. Higher circulating concentration of copper was associated with a raised CRC risk (OR = 1.50; 95% CI: 1.06, 2.13; P-trend = 0.02) whereas an inverse association with cancer risk was observed for higher zinc levels (OR = 0.65; 95% CI: 0.43, 0.97; P-trend = 0.07). Consequently, the ratio of copper/zinc was positively associated with CRC (OR = 1.70; 95% CI: 1.20, 2.40; P-trend = 0.0005). In subgroup analyses by follow-up time, the associations remained statistically significant only in those diagnosed within 2 years of blood collection. In conclusion, these data suggest that copper or copper levels in relation to zinc (copper to zinc ratio) become imbalanced in the process of CRC development. Mechanistic studies into the underlying mechanisms of regulation and action are required to further examine a possible role for higher copper and copper/zinc ratio levels in CRC development and progression.

Selenium status is associated with colorectal cancer risk in the European prospective investigation of cancer and nutrition cohort.

Suboptimal intakes of the micronutrient selenium (Se) are found in many parts of Europe. Low Se status may contribute to colorectal cancer (CRC) development. We assessed Se status by measuring serum levels of Se and Selenoprotein P (SePP) and examined the association with CRC risk in a nested case-control design (966 CRC cases; 966 matched controls) within the European Prospective Investigation into Cancer and Nutrition. Se was measured by total reflection X-ray fluorescence and SePP by immunoluminometric sandwich assay. Multivariable incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were calculated using conditional logistic regression. Respective mean Se and SePP levels were 84.0 µg/L and 4.3 mg/L in cases and 85.6 µg/L and 4.4 mg/L in controls. Higher Se concentrations were associated with a non-significant lower CRC risk (IRR = 0.92, 95% CI: 0.82-1.03 per 25 µg/L increase). However, sub-group analyses by sex showed a statistically significant association for women (p(trend) = 0.032; per 25 µg/L Se increase, IRR = 0.83, 95% CI: 0.70-0.97) but not for men. Higher SePP concentrations were inversely associated with CRC risk (p(trend) = 0.009; per 0.806 mg/L increase, IRR = 0.89, 95% CI: 0.82-0.98) with the association more apparent in women (p(trend) = 0.004; IRR = 0.82, 95% CI: 0.72-0.94 per 0.806 mg/L increase) than men (p(trend) = 0.485; IRR = 0.98, 95% CI: 0.86-1.12 per 0.806 mg/L increase). The findings indicate that Se status is suboptimal in many Europeans and suggest an inverse association between CRC risk and higher serum Se status, which is more evident in women.

Titanium coating with mussel inspired polymer and bio-orthogonal chemistry enhances antimicrobial activity against Staphylococcus aureus.

Implant-associated infections present severe and difficult-to-treat complications after surgery, related to implant biofilm colonization. Systemic administration of antibiotics cannot reach sufficient concentrations at the infected site and may be toxic. Here we describe how mussel-inspired dendritic material coated on a titanium surface can locally activate a prodrug of daptomycin (pro-dapto) to treat methicillin-resistant Staphylococcus aureus. The mechanism of the prodrug activation is based on bio-orthogonal click chemistry between a tetrazine (Tz) and trans-cyclooctene (TCO). The former is attached to the dendritic polymer, while the later converts daptomycin into a prodrug. Characterization of the material's properties revealed that it is hydrophobic, non-toxic, and stable for a prolonged period of time. We envision that the titanium coated dendritic material will be able to improve the treatment of implant-associated infections by concentrating systemically administered antibiotic prodrugs, thus converting them into active localized medicines.

Release of different amphotericin B formulations from PMMA bone cements and their activity against Candida biofilm.

Amphotericin B is used for local delivery from polymethylmethacrylate to treat fungal prosthetic joint infections. The optimal amphotericin B formulation and the influence of different poragens in the bone cements are unknown. To investigate the necessary amount of amphotericin B in the bone cement to prevent Candida biofilm several amphotericin B formulations were studied: non-liposomal and liposomal with or without poragen gentamicin. For the non-liposomal formulation, standard bile salt, the sodium deoxycholate, was used and additionally N-methyl-D-glucamine/palmitate was applied. The activity of the released amphotericin B was tested against C. albicans, C. glabrata, C. parapsilosis and C. krusei biofilms with application of the isothermal calorimeter and standard microbiological methods. Compressive strength was measured before and after antifungal elution from the cements. There is less aggregated N-methyl-D-glucamine/palmitate amphotericin B released but its antifungal activity is equivalent with the deoxycholate amphotericin B. The minimum quantity of antifungal preventing the Candida biofilm formation is 12.5 mg in gram of polymer powder for both non-liposomal formulations. The addition of gentamicin reduced the release of sodium deoxycholate amphotericin B. Gentamicin can be added to N-methyl-D-glucamine/palmitate amphotericin B in order to boost the antifungal release. When using liposomal amphotericin B more drug is released. All amphotericin B formulations were active against Candida biofilms. Although compressive strength slightly decreased, the obtained values were above the level of strength recommended for the implant fixation. The finding of this work might be beneficial for the treatment of the prosthetic joint infections caused by Candida spp.

Electro-responsive graphene oxide hydrogels for skin bandages: The outcome of gelatin and trypsin immobilization.

A free radical polymerization method was adopted for the fabrication of hybrid hydrogel films based on acrylamide and polyethylene glycol dimethacrylate as plasticizing and crosslinking agents, respectively, to be employed as smart skin bandages. Electro-sensitivity, biocompatibility and proteolytic properties were conferred to the final polymer networks by introducing graphene oxide (0.5% w/w), gelatin or trypsin (10% w/w) in the polymerization feed. The physical chemical and mechanical characterization of hybrid materials was performed by means of determination of protein content, Raman spectroscopy, thermogravimetric analysis and measurement of tensile strength. The evaluation of both water affinity and curcumin release profiles (analyzed by suitable mathematical modelling) upon application of an external electric stimulation in the 0-48 voltage range, confirmed the possibility to modulate the release kinetics. Proper proteolytic tests showed that the trypsin enzymatic activity was retained by 80% upon immobilization. Moreover, for all samples, we observed a viability higher than 94% in normal human fibroblast cells (MRC-5), while a reduction of methicillin-resistant Staphylococcus aureus CFU mL-1 (90%) was obtained with curcumin loaded samples.

Bio-Orthogonal Chemistry and Reloadable Biomaterial Enable Local Activation of Antibiotic Prodrugs and Enhance Treatments against Staphylococcus aureus Infections.

Systemic administration of antibiotics can cause severe side-effects such as liver and kidney toxicity, destruction of healthy gut bacteria, as well as multidrug resistance. Here, we present a bio-orthogonal chemistry-based strategy toward local prodrug concentration and activation. The strategy is based on the inverse electron-demand Diels-Alder chemistry between trans-cyclooctene and tetrazine and involves a biomaterial that can concentrate and activate multiple doses of systemic antibiotic therapy prodrugs at a local site. We demonstrate that a biomaterial, consisting of alginate hydrogel modified with tetrazine, is efficient at activating multiple doses of prodrugs of vancomycin and daptomycin in vitro as well as in vivo. These results support a drug delivery process that is independent of endogenous environmental markers. This approach is expected to improve therapeutic efficacy with decreased side-effects of antibiotics against bacterial infections. The platform has a wide scope of possible applications such as wound healing, and cancer and immunotherapy.