Polydopamine-Assisted Surface Modification of Ti-6Al-4V Alloy with Anti-Biofilm Activity for Dental Implantology Applications

Coating the surfaces of implantable materials with various active principles to ensure inhibition of microbial adhesion, is a solution to reduce infections associated with dental implant. The aim of the study was to optimize the polydopamine films coating on the Ti-6Al-6V alloy surface in order to obtain a maximum of antimicrobial/antibiofilm efficacy and reduced cytotoxicity. Surface characterization was performed by evaluating the morphology (SEM, AFM) and structures (Solid-state 13C NMR and EPR). Antimicrobial activity was assessed by logarithmic reduction of CFU/mL, and the antibiofilm activity by reducing the adhesion of Escherichia coli, Staphylococcus aureus, and Candida albicans strains. The release of NO was observed especially for C. albicans strain, which confirms the results obtained for microbial adhesion. Among the PDA coatings, for 0.45:0.88 (KMnO4:dopamine) molar ratio the optimal compromise was obtained in terms of antimicrobial activity and cytotoxicity, while the 0.1:1.5 ratio (KMnO4:dopamine) led to higher NO release and implicitly the reduction of the adhesion capacities only for C. albicans, being slightly cytotoxic but with moderate release of LDH. The proposed materials can be used to reduce the adhesion of yeast to the implantable material and thus inhibit the formation of microbial biofilms.

Removal of Coliphage MS2 Using a Microbial Fuel Cell Stack

Bioelectrochemical technologies offer alternative ways of treating wastewater and using this process to generate electricity. However, research in this area is just beginning to consider environmental transmission of viruses present in wastewater. The viral fecal indicator coliphage MS2 (the most frequently used pathogen model) was used in this study, since it is a well-known indigenous wastewater virus. The scaled-up bioelectrochemical system had a working volume of 167 L and coliphage MS2 concentration decreased from 8000 to 285 PFU/mL. The kinetics were quantified up to 15 h, after which excessive yeast growth in the system prevented further bacteriophage determination. The logarithmic reduction value (LRV) calculated within the first three hours was 3.8. From 4 hours to 14, LRV values were from 4.1 to 4.8, and in hour 15 the LRV increased to 5.3, yielding a more than 90% reduction. Overall, results obtained indicate that the scaled-up bioelectrochemical treatment system was efficient in reducing coliphage MS2 densities and could be used as a model to explore its further applicability for the reduction of viruses or pathogens in treated effluents.

A green synthesis method to tune the morphology of CuO and ZnO nanostructures

Background: Green synthesis of nanomaterials has gained interest over the years as it has many benefits compared to the conventional methods. Green methods are non-toxic and economic, due to the use of aqueous extracts as reducing agents Yerba mate is a widely used herb in South America, showing an available and economic alternative to conventional methods Methods: Different copper and zinc nanostructures were obtained using yerba mate extract (Ilex paraguariensis) as reducing and capping agent. Furthermore, adjusting NaCl concentration and temperature, it was possible to successfully tune and examine the morphology of the resulting nanostructures by scanning electron microscopy (SEM). Phenolic oxidation was evaluated by Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR), to assess the role of yerba mate extract in the reaction. Moreover, antimicrobial activity versus Pseudomonas aeruginosa was assayed and antioxidant activity was performed by DPPH method. Results and Conclusion: The present study reveals a powerful method to obtain zinc and copper nanostructures, showing a logarithmic reduction of Pseudomonas aeruginosa of 2.14 and 5.92 CFU/mL at 96 hours respectively and scavenger activity of 42% and 22% respectively. These properties highlight the potential of the nanomaterials for applications in catalysis, textile, biomedical and agricultural fields.

ANTIBACTERIAL ACTIVITY OF SOME NANO-ANTIMICROBIAL POLY(AMIDOAMINE) (PAMAM) DENDRIMERIC PRODUCTS

"Dendrimers are synthetic, branched macromolecules. Compared to linear polymers, dendrimers hold multiple advantages as potential carrier molecules: high capacity to incorporate pharmacologically active substances, chemical stability of micelles under physiological conditions, increased bioavailability of active substances covalently or noncovalently bound to dendrimers, due to increased dendrimers capacity to cross biological barriers. The carrier potential of dendrimers has been evaluated in combination with different antibiotics, as an alternative way to address the increasing resistance of Gram-positive and Gram-negative bacteria. This paper presents a study on the intrinsic antibacterial properties of the following poly(amidoamino) (PAMAM) ethylenediamine core dendrimers: PAMAM generation 3.5, PAMAM generation 4.0 and PAMAM-OH generation 4.0. The following bacterial strains were used: Staphylococcus aureus ATCC 29213, Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 15442, Enterococcus faecalis ATCC 51299 and a multi-drug resistant (MDR) Acinetobacter baumannii clinical isolate. The dendrimers’ concentrations used in the experiment were established within the range of admissibility obtained following cytotoxicity testing on human cell cultures. The dendrimers’ antibacterial activity varied depending on the concentration and the bacterial species. The antibacterial efficacy was quantified by calculating the percentage and logarithmic reduction of the number of viable microorganisms. The logarithmic reduction varied between 0.06 and 1.10, corresponding to percentage reductions between 13% and 92%. The strongest antibacterial activity of all dendrimers used in this study was registered for the D3.5 dendrimer (50 μg/mL) against Acinetobacter baumannii and Pseudomonas aeruginosa ATCC 15442 reference strain. For A. baumannii, a logarithmic reduction of bacterial activity of 1.10 log10 (percentage reduction in the number of CFU of 92%) was registered, while for P. aeruginosa ATCC 15442 the logarithmic reduction was 0.75 log10 (percentage reduction of 82%)."

A global disinfectant standard for cleanrooms: Presenting a harmonised approach

Disinfectant efficacy testing is an essential part of a facility contamination control strategy. Pharmaceutical and healthcare products facilities must know that the products they are using can achieve effective levels of microbial kill across a range of surface types. The problem faced by microbiologists and production managers is that the various national and international standards use different methodologies. In addition, these standards and methods have not been written specifically for cleanrooms and the microbial test panels and logarithmic reduction expectations are not considered suitable. In order to develop an international standard suitable for all pharmaceutical facility cleanrooms, Ecolab has developed the Validex™ method, which is independently assessed in this paper. This method involves using 2 cm diameter disks, to target a 3 log reduction for vegetative bacteria in 5 minutes; and a 2 log reduction for fungi and bacterial spores in 10 minutes. The key criteria and rationale for selection, along with the methodology, are presented in this paper.

Effect of essential oils of oregano (Origanum vulgare), thyme (Thymus vulgaris), orange (Citrus sinensis var. Valencia) in the vapor phase on the antimicrobial and sensory properties of a meat emulsion inoculated with Salmonella enterica

The demand for healthier meat products is increasing remarkably and natural antimicrobial agents such as essential oils (EOs) are required, which can be applied in the vapor phase. For this experiment, the effectiveness of essential oils of oregano, thyme, and orange in the vapor phase on the microbiological and sensory characteristics of sausages inoculated with Salmonella enterica and stored at 4°C during 72 hrs and 144 hrs, were studied. Oregano EO with 2000 ppm was the most effective treatment against Salmonella enterica with a logarithmic reduction of 1.97 Log10 CFU/g compared to thyme 1.36 Log10 CFU/g and orange 1 Log10 CFU/g) after 144 hrs. In relation to the general acceptance level, the meat product exposed to the orange EO in vapor phase presented the highest approval by the judges nevertheless, however, were the ones that showed the least reduction in the microbial population. Finally, the results showed that the addition of essential oil in the vapor phase to meat products exerted a bactericidal effect with higher EOs concentrations and some also caused alterations in the sensorial properties of the product.

Aspects regarding the effectiveness of volatile oils of the Tanacetum vulgare kind in the conservation of heritage objects

The paper refers to a composition with antifungal and antibacterial effect in order to test new materials for preserving heritage objects on collagen support with bactericidal/antifungal role, essential oils-based from Vetrice (Tanacetum vulgare, Compositae family), having antifungal and antibacterial properties. The biocidal effect of plant extracts is due to the presence of constituent agents, such as alcohols, ethers, phenols, aldehydes, ketones, which makes them extremely effective against a wide range of microbial strains. The essential oil was obtained by boiling the plants through continuous hydrodistillation with Clevenger refrigerant. The testing of the antimicrobial efficiency of the plant extracts was performed on two strains of pathogenic fungi, respectively Trichophyton interdigitale and Epidermophyton floccosum. The microbial inoculum was mixed with the plant extract from various sources (leaves, flowers and mixed flower-leaves). All extracts were tested in duplicate according to the specific test standards, and the results were expressed as a mean percentage and logarithmic reduction between the readings on the two Petri plates corresponding to each sample. To quantify the antimicrobial efficacy, the degree of microbial and logarithmic reduction of each sample was calculated, relative to the initial cell concentration. The results of antimicrobial tests showed a high antifungal character of the extracts obtained from flowers, leaves and mixed flower-leaves.

Statistical calibration of microbial suspensions in carrier controls during a textile disinfection ring trial

IntroductionThe high number of uncontrollable variables in microbiological systems increases experimental complexity and reduces accuracy, potentially leading to data misinterpretation or uncorrectable errors. During an interlaboratory calibration analysis it was observed that the microbial logarithmic reduction (LR) caused by disinfectants depends not only on the type of disinfectant but also on the initial microbial load in the fabric carriers, which can produce a misinterpretation of the results. Fabric carriers are commonly used in standard tests such as EN16616 and ASTM2274.ObjectiveA method based on statistical calibration is proposed using a regression line between N0 (initial microbial load in the carrier) and LR to eliminate the influence of one on the other.ResultsAn example with Candida albicans is presented. Once the method was applied, the influence of N0 on LR was eliminated and the new LR values can be used for factorial experiments, for example, to check the efficacy of disinfectants or detergents without depending on the microbial load placed in the carrier.

Iterative Cochran’s C test as a multivariate method to detect higher than expected variability: a microbiological inter-laboratory ring trial as a case-study

IntroductionAn interlaboratory calibration analysis was carried out to validate a methodology for a European standard for domestic laundry disinfection, using different doses of disinfectant and microorganisms. ISO 5725-2 and ISO 13528 form the basis of interlaboratory validations of quantitative methods, but there is a need for a simple graphical method to detect differences in laboratory behavior in terms of accuracy and variability.ObjectiveA novel multivariate method based on the classical Cochran’s C test, as well as PCA and bootstrapping, which allows the inclusion of different correlated variables, was applied to identify higher variability than expected in factor (e.g. laboratories) levels, and the detection of multivariate outliers in a reduced space.MethodsThe proposed method is based on resampling, using the same sample many times but removing cases at random and performing Cochran’s C test for all the variables together in a reduced space.ResultsThe method was tested by checking 7 laboratories for high variability in different parameters (logarithmic reduction (LR), cross contamination (RI), and wash water (WW)). After applying the proposed statistical analyses, no reasons were found to reject any of the participating laboratories. Multiple applications of the method are possible and we describe a case study in which the multivariant iterative Cochran’s C test was used: variability detection with multiple microbiological parameters (with high variability) during an interlaboratory ring trial.

Did Granny know best? Evaluating the Antibacterial, Antifungal and Antiviral Efficacy of Acetic Acid for Home Care Procedures.

Background: Acetic acid has been used to clean and disinfect surfaces in the household for many decades. The antimicrobial efficacy of cleaning procedures can be considered particularly important for young, old, pregnant, immunocompromised people, but may also concern other groups, particularly with regards to the COVID-19 pandemics. This study aimed to show that acetic acid exhibit an antibacterial and antifungal activity when used for cleaning purposes and is able to destroy certain viruses. Furthermore, a disinfecting effect of laundry in a simulated washing cycle has been investigated.Results: At a concentration of 10% and in presence of 1.5% citric acid, acetic acid showed a reduction of >5-log steps according to the specifications of DIN EN 1040 and DIN EN 1275 for the following microorganisms: P. aeruginosa, E. coli, S. aureus, L. monocytogenes, K. pneumoniae, E. hirae and A. brasiliensis. For MRSA a logarithmic reduction of 3.19 was obtained. Tests on surfaces according to DIN EN 13697 showed a complete reduction (> 5-log steps) for P. aeruginosa, E. coli, S. aureus, E. hirae, A. brasiliensis and C. albicans at an acetic acid concentration of already 5%. Virucidal efficacy tests according to DIN EN 14476 and DIN EN 16777 showed a reduction of ≥ 4-log-steps against the Modified Vaccinia virus Ankara (MVA) for acetic acid concentrations of 5% or higher.The results suggest that acetic acid does not have a disinfecting effect on microorganisms in a dosage that is commonly used for cleaning. However, this can be achieved by increasing the concentration of acetic acid used, especially when combined with citric acid.Conclusions: Our results show a disinfecting effect of acetic acid in a concentration of 10% and in presence of 1.5% citric acid against a variety of microorganisms. A virucidal effect against enveloped viruses could also be proven. Furthermore, the results showed a considerable antimicrobial effect of acetic acid when used in domestic laundry procedures.