Spectrophotometric Readings Research Articles

Antibacterial Activity and Prebiotic Properties of Six Types of Lamiaceae Honey.

Our work investigated the antimicrobial and prebiotic properties of basil, mint, oregano, rosemary, savory, and thyme honey. The potential antimicrobial action, assessed against the pathogens Acinetobacter baumannii, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, and Staphylococcus aureus, evidenced the capacity of the honey to influence the pathogenic hydrophobicity and hemolytic activities. Honey inhibited pathogen biofilms, acting especially on the mature biofilms, with inhibition rates of up to 81.62% (caused by the presence of mint honey on L. monocytogenes). S. aureus biofilms were the most susceptible to the presence of honey, with inhibition rates up of to 67.38% in the immature form (caused by basil honey) and up to 80.32% in the mature form (caused by mint honey). In some cases, the amount of nuclear and proteic material, evaluated by spectrophotometric readings, if also related to the honey's biofilm inhibitory activity, let us hypothesize a defective capacity of building the biofilm scaffold or bacterial membrane damage or an incapability of producing them for the biofilm scaffold. The prebiotic potentiality of the honey was assessed on Lacticaseibacillus casei Shirota, Lactobacillus gasseri, Lacticaseibacillus paracasei subsp. paracasei, and Lacticaseibacillus rhamnosus and indicated their capacity to affect the whole probiotic growth and in vitro adhesive capacity, as well as the antioxidant and cytotoxic abilities, and to inhibit, mainly in the test performed with the L. casei Shirota, L. gasseri, and L. paracasei supernatants, the immature biofilm of the pathogens mentioned above.

The effectiveness of antimicrobial photodynamic therapy on catheter infection model

Background/AimThis experimental study aimed to examine the effectiveness of transdermal antimicrobial photodynamic therapy (APDT) with and without antimicrobial lock therapy (ALT), on catheter biofilms. MethodsS. epidermidis and C. orthopsilosis biofilms were formed within peripheral venous catheters positioned in the marginal ear veins of New Zealand white rabbits. Biofilm formation was confirmed with scanning electron microscopy in two catheters. 24 catheters with staphylococcal biofilms and 24 with fungal biofilms were treated with APDT, ALT or “APDT plus ALT” for five days. Six catheters were separated as controls. APDT was applied with a red colored LED lamp and methylene blue as the photosensitizer. Vancomycin lock solutions were used as ALT for staphylococcal biofilms and amphotericin B for fungal biofilms. The effect of treatment procedures was evaluated by intraluminal biofilm viability testing based on spectrophotometric evaluation, and a quantitative (OD) value was obtained for each catheter. ResultsThe mean OD values obtained by 600 nm spectrophotometric reading at 24 h (biofilm viability) after “ALT”, “APDT” and “ALT plus APDT” procedures were 0.363, 0.151 and 0.128 for S. epidermidis and 0.092, 0.104 and 0.227 for C. orthopsilosis, respectively. All these OD values obtained after treatment procedures were lower than controls for both S. epidermidis (OD: 0,802) and C. orthopsilosis (OD: 0,315), although there were large fluctuations in our results. ConclusionsOur results suggest that transdermal APDT may be an effective method for treating staphylococcal and candida biofilms formed within intravenous catheters in our rabbit ear model. The combined use of APDT and ALT might be beneficial in these staphylococcal biofilms.

Twenty Years in EUCAST Anti-Fungal Susceptibility Testing: Progress & Remaining Challenges.

Since its inception in 2002, the EUCAST Antifungal Susceptibility Testing Subcommittee (AFST) has developed and refined susceptibility testing methods for yeast, moulds and dermatophytes, and established epidemiological cut-off values and breakpoints for antifungals. For yeast, three challenges have been addressed. Interpretation of trailing growth in fluconazole susceptibility testing, which has been proven without impact on efficacy if below the 50% endpoint. Variability in rezafungin MIC testing due to laboratory conditions, which has been solved by the addition of Tween 20 to the growth medium in E.Def 7.4. And third, interpretation of MICs for rare yeast with no breakpoints, where recommendations have been established for MIC-based clinical advice. For moulds, refinements include the validation of spectrophotometer reading for A. fumigatus to facilitate objective MIC determination, and for dermatophytes the establishment of a microdilution method with automated reading and a selective medium to minimise the risk of contaminations. Recent initiatives involve development and validation of agar-based screening assays for detection of potential azole and echinocandin resistance in A. fumigatus and Aspergillus species, respectively, and of terbinafine resistance in Trichophyton species. Moreover, the development of a EUCAST guidance document for molecular resistance testing represents an advancement, particularly for identifying target gene alterations associated with resistance. In summary, EUCAST AFST continues to play a pivotal role in standardizing AFST and facilitating accurate interpretation of susceptibility data for clinical decision-making. Adoption of EUCAST breakpoints for commercial test methods, however, requires thorough validation to ensure concordance with EUCAST reference testing species-specific MIC distributions.

Differentiation of Saccharomyces boulardii from Saccharomyces cerevisiae Strains Using the qPCR-HRM Technique Targeting AAD15 Gene

ABSTRACT S. boulardii, the probiotic variety of S. cerevisiae, is known for its different characteristics, even though the two strains share more than 99% genomic relatedness. Therefore, S. boulardii has been examined and evaluated for differential characteristics in many studies. This study aims to explain the differentiation of S. boulardii from well-identified S. cerevisiae strains by biochemical characteristics and the qPCR-HRM. Initially, S. cerevisiae isolates from the HUF Culture Collection, were screened for basic biochemical characteristics such as growth temperature, glucose, and galactose utilization tests. Out of all selected cultures, the viability at gastric pH was investigated by spectrophotometric readings. The results showed that one isolate was more resistant than other strains when exposed to gastric acids. After sequencing and phylogeny steps using LR0R universal primer, there was no significant differentiation for S. boulardii strains and therefore HRM analysis was performed to interrogate sequence variation and differentiate S. boulardii strains. HRM analysis has successfully distinguished even highly closely related yeast strains.

Genetic Variation and Heritability for Hydrogen Cyanide in Fresh Cassava Roots: Implications for Low-Cyanide Cassava Breeding.

Breeding for low-hydrogen-cyanide (HCN) varieties is a major objective of programs targeting boiled cassava food products. To enhance the breeding of low-HCN varieties, knowledge of genetic variation and trait heritability is essential. In this study, 64 cassava clones were established across four locations and evaluated for HCN using three HCN assessment methods: one with a 1 to 9 scale, on with a 0 ppm to 800 ppm scale, and a quantitative assay based on spectrophotometer readings (HCN_Spec). Data were also collected on the weather variables precipitation, relative humidity, and temperature. Highly significant differences were observed among clones (p < 0.001) and locations (p < 0.001). There was also significant clone-environment interactions, varying from p < 0.05 to p < 0.001. Locations Arua and Serere showed higher HCN scores among clones and were associated with significantly higher (p < 0.001) mean daily temperatures (K) and lower relative humidity values (%) across 12 h and 18 h intervals. Within locations, HCN broad sense heritability estimates ranged from 0.22 to 0.64, while combined location heritability estimates ranged from 0.14 to 0.32. Relationships between the methods were positive and strong (r = 0.75-0.92). The 1 to 9 scale is more accurate and more reproducible than either the 0 to 800 ppm scale or spectrophotometric methods. It is expected that the information herein will accelerate efforts towards breeding for low-HCN cassava varieties.

The effect of the probiotic drug "Ecoflor" on the proteolytic activity of the sterlet intestine

The effect of the probiotic preparation "Ecoflor" on proteolytic activity of the intestinal mucosa and chyme of sterlet was studied. This probiotic is a consortium of strains of lacto- and bifidobacteria: B. bifidum, B. longum and L. acidophilus, L. casei, L. plantarum, immobilized on carbon-mineral sorbent SUMS-1. For the experiment, fish were divided into 4 groups: control and three experimental groups. Experimental groups of fish were given feed with probiotic in the amount of 2, 4, 6 g/kg of feed. Sampling was carried out before the beginning of the experiment, on 7, 14, and 21 days. Material for the study was taken from 5 individuals from each group. To obtain enzymatically active preparations, fish intestines were freed from fat and dried on ice bath glass. After incision, the chyme was collected with a spatula and scraper, then the mucous membrane was removed. The total proteinase activity was calculated by the ratio of the difference between the spectrophotometer readings of the sample with substrate and the blank sample to the product of the intestinal weight (g) by the incubation time (min) EA = ΔE425/(g×min). Determinations were performed in three repetitions. Data analysis showed the stimulating effect of the preparation on proteolytic activity. The maximum increase in enzymatic activity in the experimental groups compared to the control group was recorded on the 7th day of the experiment. A more significant increase in proteolytic activity of the intestinal mucosa compared to chyme was found. At the beginning of feeding, the stimulating effect of the preparation was found in all experimental groups compared to the control. In further observation periods the effectiveness of the probiotic significantly decreased.

Microwell fluoride assay screening for enzymatic defluorination.

There is intense interest in removing fluorinated compounds from the environment, environments are most efficiently remediated by microbial enzymes, and defluorinating enzymes are readily monitored by fluoride determination. Fluorine is the most electronegative element. Consequently, all mechanisms of enzymatic C-F bond cleavage produce fluoride anion, F-. Therefore, methods for the determination of fluoride are critical for C-F enzymology and apply to any fluorinated organic compounds, including PFAS, or per- and polyfluorinated alkyl substances. The biodegradation of most PFAS chemicals is rare or unknown. Accordingly, identifying new enzymes, or re-engineering the known defluorinases, will require rapid and sensitive methods for measuring fluoride in aqueous media. Most studies currently use ion chromatography or fluoride specific electrodes which are relatively sensitive but low throughput. The methods here describe refashioning a drinking water test to efficiently determine fluoride in enzyme and cell culture reaction mixtures. The method is based on lanthanum alizarin complexone binding of fluoride. Reworking the method to a microtiter well plate format allows detection of as little as 4nmol of fluoride in 200μL of assay buffer. The method is amenable to color imaging, spectrophotometric plate reading and automated liquid handling to expedite assays with thousands of enzymes and/or substrates for discovering and improving enzymatic defluorination.

Does the Ethnomedicinal Use of Pequi Oil for the Treatment of Infections Reveal its Antifungal Potential?

In Brazil, the use of medicinal plants has been on the rise over the years, especially as an alternative for the treatment of diseases caused by fungal infections. Fungal infections have become a major public health problem, primarily due to the indiscriminate and prolonged use of antibiotics. In this context, among the various species of the Brazilian flora, an endemic species stands out, Caryocar coriaceum, popularly known as "pequi," is widely used in nutrition and is also employed by the population for medicinal purposes to treat infectious diseases. Thus, this study aims to evaluate the chemical composition, antifungal action of the medicinal oil from Caryocar coriaceum, test the combined effect with the drug Fluconazole, and finally determine the chemical constituents present in the oil of pequi fruits. Initially, the fruits of this species were subjected to boiling in broth microdilution, and the combined effect with Fluconazole was assessed at sub-inhibitory concentrations (1/8 MIC), followed by spectrophotometric readings used to determine the IC50. The C. coriaceum species is composed of four fatty acids, of which two were more prevalent, oleic acid and palmitic acid. The fixed oil showed low antifungal activity when evaluated individually for Candida albicans and Candida tropicalis strains, with IC50 values of 593.8 μg/mL, exhibiting greater modification for the standard drug with IC50 values for C. albicans at 16.07 μg/mL and C. tropicalis at 4.77 μg/mL. However, for the Candida krusei strain, the fixed oil exhibited more potent antifungal activity than Fluconazole at concentrations of 32 μg/mL and 64 μg/mL, while Fluconazole had intensified activity at concentrations from 2 μg/mL up to 128 μg/mL. Regarding the potentiating action for Candida albicans, Candida tropicalis and Candida krusei strains, the oil associated with Fluconazole enhanced the antifungal effect with IC50 values of 0.02792 μg/mL for C. albicans, 0.09903 μg/mL for C. tropicalis, and 15.15 μg/mL for C. krusei. Thus, the oil contains promising compounds in its composition for the development of medications to treat infectious diseases.

Optimization of the EUCAST reference broth microdilution method for echinocandin susceptibility testing of Aspergillus fumigatus.

Because of the high inoculum (105 cfu/mL) used in the EUCAST susceptibility testing of Aspergillus spp., determination of the minimal effective concentration (MEC) of echinocandins is challenging as the morphological differences are subtle. The MECs of 10 WT and 4 non-WT Aspergillus fumigatus isolates were determined with the EUCAST E.Def 9.4. Plates were inoculated with increasing inocula (102-105 cfu/mL) and after 24 and 48 h of incubation, MECs were determined macroscopically (magnifying mirror) and microscopically (inverted microscope) by two observers, spectrophotometrically (OD at 405 nm) and colorimetrically (absorbance at 450/630 nm after 2 h incubation with 400 mg/L XTT/6.25 μM menadione). The interobserver (between observers)/intermethod (compared with the microscopic method) essential agreement (EA, ±1 2-fold dilution) and categorical agreement (CA) were determined for each inoculum. Echinocandin-induced microscopic hyphal alterations or macroscopic changes in turbidity were subtle with a 105 cfu/mL inoculum compared with the lower inocula of 103 and 102 cfu/mL, where more distinct changes in turbidity and formation of characteristic rosettes were obvious at the MEC after 48 h. A 105 cfu/mL inoculum resulted in wider MEC distributions (3-6 dilutions) and lower interobserver EA (69%), macroscopic-microscopic EA (26%) and CA (71%) compared with a 103 cfu/mL inoculum (2-3 dilutions, 100%, 100% and 100%, respectively). Spectrophotometric readings using a 103 cfu/mL inoculum showed good EA (57-93%) and excellent CA (86%-100%), while the XTT assay demonstrated excellent EA (93%) and CA (100%). A 48 h incubation using a 103 cfu/mL inoculum improved echinocandin MEC determination for A. fumigatus with the EUCAST method, while the colorimetric assay could allow automation.

β-Glucosidase activity and antimicrobial properties of potentially probiotic autochthonous lactic cultures.

The demand for lactic acid bacteria products, especially probiotics, has increased. Bacteria that increase polyphenol bioavailability and act as bio preservatives are sought after. This study aims to identify autochthonous lactic acid cultures from EMBRAPA that demonstrate β-glucosidase activity and inhibitory effect on microbial sanitary indicators. Cell-free extracts were obtained by sonicating every 5 s for 40 min. The extracts were mixed with cellobiose and incubated at 50 °C. The reaction was stopped by immersing the tubes in boiling water. The GOD-POD reagent was added for spectrophotometer readings. Antimicrobial activity was tested against reference strains using the agar well diffusion method. Lactic cultures in MRS broth were added to 0.9 cm wells and incubated. The diameter of the inhibition zones was measured to determine the extension of inhibition. Only L. rhamnosus EM1107 displayed extracellular β-glucosidase activity, while all autochthonous strains except L. plantarum CNPC020 demonstrated intracellular activity for this enzyme. L. plantarum CNPC003 had the highest values. On the other hand, L. plantarum CNPC020, similarly to L. mucosae CNPC007, exhibited notable inhibition against sanitary indicators. These two strains significantly differed from the other five autochthonous cultures regarding S. enterica serovar Typhimurium ATCC 14028 inhibition (P < 0.05). However, they did not differ from at least one positive control in terms of inhibition against S. aureus ATCC 25923 and E. coli ATCC 25922 (P > 0.05). Therefore, it is advisable to consider these cultures separately for different technological purposes, such as phenolics metabolism or bio preservative activity. This will facilitate appropriate selection based on each specific property required for the intended product development.

PENENTUAN KADAR KAFEIN DALAM BUNGA, BIJI, KULIT BUAH DAN DAUN KOPI ARABIKA (Coffea arabica) WONOLELO MENGGUNAKAN SPEKTROFOTOMETER UV

Arabica coffee is a type of coffee that is widely cultivated in Indonesia. Caffeine is one of the secondary metabolites contained in coffee with various biological benefits. Caffeine belongs to the class of alkaloids of the methylxanthine group. Caffeine is distributed in different parts of the coffee plant in the leaves, cotyledons and flowers. Various studies have proven that the caffeine content in each part of the coffee plant has varying levels. This study aims to determine which part of the Arabica coffee plant comes from Wonolelo, Temanggung with the highest caffeine content.&#x0D; Powder of flowers, leaves, seeds and fruit skins of Arabica coffee were extracted with distilled water and then extracted liquid-liquid with chloroform, the chloroform fraction obtained was evaporated to form crystals containing caffeine. The results were analyzed quantitatively by UV spectrophotometry. The absorbance results were obtained from UV spectrophotometric readings, then the caffeine content in the sample was calculated and analyzed using SPSS software.&#x0D; Quantitative test stated that the highest to the lowest caffeine content were fruit peels of 3.232%, seeds (0.771%), flowers (0.509%), and leaves (0.24%). The results of this study are different compared to previous studies. This can occur due to differences in extraction methods, sample age, roasting conditions, grinding degree, geographical origin, such as growing locations at different altitudes, soil types, rainfall, harvest time, and intensity of exposure to sunlight.

Composição centesimal, minerais, taninos, fitatos e qualidade de cozimento de cultivares comerciais de feijão-caupi

ABSTRACT Cowpea is a socioeconomically important legume in the Northeast region of Brazil, and the most grown and consumed type of bean, representing the main source of low-cost vegetable protein for rural and urban populations in this region. The objective of this work was to characterize the proximate composition, minerals, tannins, phytic acid, and cooking quality of whole grains of cowpea from the commercial cultivars BRS Aracê, BRS Inhuma, and BRS Xiquexique. Grain samples of the cultivars were ground in a zirconium ball mill and the flour was used for analysis. The proximate composition was carried out according to the AOAC methodology. The minerals were determined by nitro-perchloric digestion and reading in a flame atomic absorption spectrophotometer. The anti-nutritional factors tannins and phytic acid were determined by extraction and reading in a spectrophotometer. Cooking quality was assessed using an electric pressure cooker and then a Mattson cooker. A completely randomized experimental design was used, with three treatments (cultivars) and three replications. The data were subjected to analysis of variance and the means were compared by the Tukey's test (p&lt;0.05). The cowpea cultivars showed significant differences (p&lt;0.05) for most characteristics evaluated and were similar in terms of ash, lipids, total dietary fiber, and most macrominerals. The results showed that grains of the cultivars BRS Aracê and BRS Xiquexique are excellent sources of dietary fiber, proteins, and minerals and present high cooking quality, while grains of the cultivar BRS Inhuma stood out regarding carbohydrates, soluble dietary fibers, total energetic value, and low levels of factors, anti-nutritional tannins and phytic acid.

A Rapid Method to Determine Growth‐Limiting Nutrient Concentrations for Yeast in a Microplate Spectrophotometer

Determining the minimal concentration of a substance-whether a compound used to inhibit cell growth or a growth-limiting nutrient-can be an arduous process. Carrying out the experiment in flasks or tubes and estimating cell density in a single-sample spectrophotometer has been a routine method of choice due to the ease of measurement and standardized conversions from optical density measurements to cell concentrations. However, when dealing with dozens or more samples, several challenges arise, including increased processing time, increased risk of contamination through repeated sampling, and an increased risk of confounding one sample for another. The protocol described here details a rapid method to estimate cell concentrations for such experiments using a microplate spectrophotometer. Using a microplate spectrophotometer to measure optical density of many cultures can be automated for high throughput and benefits from a reduced risk of contamination. Since one of the caveats of a microplate spectrophotometer is its low saturation limit, we further describe how to convert optical density readings of the microplate spectrophotometer into its single-sample spectrophotometric equivalent. To further illustrate the applicability of this protocol, we compare OD600 readings generated using a microplate spectrophotometer and a single-sample spectrophotometer for different nutrient starvations and show that the results are comparable. Overall, this method reduces the required resources, reduces the risk of contamination, and allows for faster processing of samples. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Generating an equation to convert microplate spectrophotometer readings to single-sample spectrophotometric values Basic Protocol 2: Evaluating growth-limiting nutrient concentrations using a microplate spectrophotometer.

Amphotericin B, itraconazole, posaconazole, and isavuconazole MICs against clinical Mucorales isolates obtained by visual inspection and spectrophotometric reading according to the EUCAST 9.4 procedure.

We compared the antifungal susceptibility of 92 Mucorales isolates obtained by visual inspection and spectrophotometric readings following EUCAST (European Committee on Antimicrobial Susceptibility Testing) testing. Amphotericin B minimum inhibitory concentrations (MICs) were up to 1 mg/l against most isolates and variable among species, except for Cunninghamella bertholletiae. Posaconazole MICs against most isolates were up to 1 mg/l and high against Mucor circinelloides, some Rhizopus arrhizus, and Rhizopus microsporus. Isavuconazole MICs ranged between 1 and 8 mg/l but were invariably>8 mg/l against M. circinelloides and C. bertholletiae. The agreement between MICs obtained by visual endpoint or spectrophotometric readings was moderate and higher when using the≥90% fungal growth inhibition endpoint.

Enhancing the Antimicrobial Effect of Ozone with Mentha piperita Essential Oil

This study aimed to obtain and analyse Mentha piperita essential oil (MpEO) for the prospect of being used as an enhancement agent for the antimicrobial potential of ozone against gram-positive and gram-negative bacteria and fungi. The research was done for different exposure times, and it gained time-dose relationships and time-effect correlations. Mentha piperita (Mp) essential oil (MpEO) was obtained via hydrodistillation and further analysed by using GC-MS. The broth microdilution assay was used to determine the strain inhibition/strain mass growth by using spectrophotometric optical density reading (OD). The bacterial/mycelium growth rates (BGR/MGR) and the bacterial/mycelium inhibition rates (BIR/MIR) after ozone treatment in the presence and absence of MpEO on the ATTC strains were calculated; the minimum inhibition concentration (MIC) and statistical interpretations of the time-dose relationship and specific t-test correlations were determined. The effect of ozone on the following tested strains at maximum efficiency was observed after 55 s of single ozone exposure, in order of effect strength: S. aureus > P. aeruginosa > E. coli > C. albicans > S. mutans. For ozone with the addition of 2% MpEO (MIC), maximum efficacy was recorded at 5 s for these strains, in order of effect strength: C. albicans > E. coli > P. aeruginosa > S. aureus > S. mutans. The results suggest a new development and affinity regarding the cell membrane of the different microorganisms tested. In conclusion, the use of ozone, combined with MpEO, is sustained as an alternative therapy in plaque biofilm and suggested as helpful in controlling oral disease-causing microorganisms in medicine.

The Effect of a Setting Accelerator on the Physical and Mechanical Properties of a Fast-set White Portland Cement Mixed with Nano-zirconium Oxide.

This study compared the effects of calcium chloride dihydrate (CaCl2.2H2O) on the physical properties and push-out bond strength of white Mineral Trioxide Aggregate (WMTA) and an experimental Malaysian Portland cement mixed with nano-zirconium oxide (nano-ZrO) [(radiopaque Malaysian Portland cement (RMPC). Mineral Trioxide Aggregate (MTA) was the first calcium silicate cement (CSC) introduced in dentistry, but up to date, it is an expensive cement with long setting time and causes tooth discolouration. Although Portland cement has been introduced as a potential substitute to MTA, it still faces some challenges such as long setting time and lack of sufficient radiopacity. Four groups [WMTA, RMPC, fast-set WMTA (FS-WMTA) and fast-set RMPC (FS-RMPC)] were prepared. Initial setting time was evaluated using Vicat apparatus. The pH was measured at seven-day intervals. For discolouration potential, cements were packed in the pulp chamber of 46 extracted maxillary incisors. Spectrophotometric readings were obtained at seven-day intervals, and the rate of colour change (ΔE) was recorded. For the push-out bond strength testing, cements were applied in 48 sectioned root samples, and the test was performed using universal testing machine at crosshead speed of 0.5 mm/min until bond failure. Statistical analysis was done according to the nature of each group of data using SPSS 26. Addition of CaCl2.2H2O decreased the initial setting times of both RMPC and WMTA significantly (p<0.05). The pH values of FS-WMTA and FS-RMPC were comparable to their non-accelerated counterparts ranging from 10 to 12. Discolouration effect was more obviously observed with WMTA and FS-WMTA with time compared to RMPC formulations. Push-out bond strength of the two materials also showed an increase with the addition of the accelerator, however, only FS-WMTA showed statistically significant difference compared to WMTA (p<0.05). The addition of CaCl2.2H2O improves the physical and mechanical properties of the newly formulated RMPC and WMTA. The RMPC formulation overcomes the discolouration potential of WMTA. (EEJ-2022-12-155).

Development and validation of a resazurin assay for in vitro susceptibility testing of Actinomadura madurae: a common causative agent of actinomycetoma.

Actinomycetoma is a chronic granulomatous disease affecting skin, subcutaneous tissue, fascia, muscle and bones. With increasing resistance against commonly used treatment regimens, susceptibility testing is urgently needed. We developed an in vitro susceptibility assay for Actinomadura madurae, one of the common causative agents of actinomycetoma, employing resazurin for endpoint reading. Using this assay, reproducible MICs were determined for the most commonly used antibacterial agents for actinomycetoma treatment. The tested antibacterial agents included trimethoprim/sulfamethoxazole, amikacin, streptomycin, amoxicillin, ceftriaxone, gentamicin, ciprofloxacin, doxycycline, imipenem, linezolid, penicillin G and rifampicin. Following the clinical breakpoints as stated by CLSI, 100% of the tested strains were susceptible to trimethoprim/sulfamethoxazole (MIC 0.03/0.59-1/19 mg/L), amikacin (MIC 0.0078-0.25 mg/L), doxycycline (MIC <0.25-1 mg/L) and linezolid (MIC <0.25-2 mg/L), 90% to ciprofloxacin (MIC <0.25-2 mg/L), 80% to ceftriaxone (MIC <0.5 to >64 mg/L) and imipenem (MIC <0.25-32 mg/L) and only 20% to amoxicillin (MIC <0.5 to >64 mg/L) and rifampicin (MIC 0.5 to >32 mg/L). Determinations of MICs by visual readings of colour changes versus spectrophotometric readings were comparable. This convenient visual reading has the advantage of feasible implementation in endemic settings.

Which whitening toothpaste with different contents is more effective on color and bond strength of enamel?

To evaluate the effects of six whitening toothpastes with different whitening ingredients as follows: abrasives, polyphosphates, activated charcoal and hydrogen peroxide on the color, and shear bond strength (SBS) of enamel. Thirty-five extracted human molars were sectioned in mesiodistal direction, providing 70 enamel specimens and randomly divided into seven groups having different whitening ingredients (n=10). After baseline color measurements, the specimens were brushed three times daily for the 30 s. At the end of 2 weeks, spectrophotometric readings were repeated, and color change parameters were calculated. Then, composite cylinders were built on the enamel surfaces and the specimens were subjected to SBS test. Failure modes were determined under a stereomicroscope (×10). One specimen from each group was examined with scanning electron microscope (SEM). The data were statistically analyzed using Kruskal-Wallis, Wilcoxon signed, one-way-ANOVA (p=0.05). Clinically acceptable color change was observed in all whitening toothpastes. There were no significant differences among the groups for Δa, ΔL, ΔE00 , and ΔWID (p > 0.05). The differences among the groups were not significant regarding SBS and failure mode distributions (p > 0.05). SEM findings were in line with the SBS test and failure mode distribution results. All the tested whitening toothpastes showed similar and clinically acceptable efficacy on the color change of the enamel and led to comparable SBS values. The tested whitening toothpastes had an acceptable whitening efficacy and did not have a negative effect on the bond strength to the enamel.

Influence of Different Illuminants on Spectrophotometric Tooth Color Determination

Statement of problem: The vast majority of studies address the comparison of visual and instrumental tooth color determination. Although, the lighting conditions of the environment may affect the clinical shade matching performance. This study evaluated if and how different light sources can influence the spectrophotometric determination of natural tooth color. Purpose: The purpose of this study was to evaluate the precision of the spectrophotometer in tooth shade determination under the influence of different illuminants. Material and method: Three examiners, determined the shade of an upper central incisor with Vitapan 3D-Master (VITA Zahnfabrik, Bad Säckingen, Germany) and with the spectrophotometer (Vita Easyshade V, Vita Zahnfabrik, Bad Säckingen, Germany). A special fabricated device with eight light sources, designed to offer reproductible lighting conditions, was used to determine the efficiency of instrumental color determination under different illuminants. Results: Natural light (300 lux) and dental unit light at full intensity (32500 lux) produced the less ∆Eab modification. Color coordinates determined in the presence of halogen light (1800 lux), neon ambient light (3000 lux), LED with cold light (21200 lux), halogen light with neon ambient light (23400 lux), both warm and cold LED simultaneously (36000 lux) and all eight light sources of the device (44000 lux), suffered a slight modification of ∆E ab, which does not exceed the acceptability and the perceptibility threshold. The illuminant that caused the biggest modifications in color coordinates was LED warm light (1940 lux) with a ∆Eab 5.804 ± 0.271, that exceeds the acceptability and perceptability threshold. Conclusions: LED warm light influences the instrumental tooth color determination and when used, can lead to errors in communication of the color to the dental laboratory, which can cause esthetic failure of a prosthetic restoration. The best illuminant for color determination is natural light, or illuminants that simulate lighting in daily living conditions. Clinical implications: Based on the spectrophotometric readings, it was demonstrated that tooth color shifts with the change in ambient lighting conditions. Therefore, color determination should be performed with natural daylight illumination.

Multicenter Collaborative Study of the Interaction of Antifungal Combinations against Candida Spp. by Loewe Additivity and Bliss Independence-Based Response Surface Analysis.

Combination antifungal therapy is widely used but not well understood. We analyzed the spectrophotometric readings from a multicenter study conducted by the New York State Department of Health to further characterize the in vitro interactions of the major classes of antifungal agents against Candida spp. Loewe additivity-based fractional inhibitory concentration index (FICi) analysis and Bliss independence-based response surface (BIRS) analysis were used to analyze two-drug inter- and intraclass combinations of triazoles (AZO) (voriconazole, posaconazole), echinocandins (ECH) (caspofungin, micafungin, anidulafungin), and a polyene (amphotericin B) against Candida albicans, C. parapsilosis, and C. glabrata. Although mean FIC indices did not differ statistically significantly from the additivity range of 0.5–4, indicating no significant pharmacodynamic interactions for all of the strain–combinations tested, BIRS analysis showed that significant pharmacodynamic interactions with the sum of percentages of interactions determined with this analysis were strongly associated with the FIC indices (Χ2 646, p < 0.0001). Using a narrower additivity range of 1–2 FIC index analysis, statistically significant pharmacodynamic interactions were also found with FICi and were in agreement with those found with BIRS analysis. All ECH+AB combinations were found to be synergistic against all Candida strains except C. glabrata. For the AZO+AB combinations, synergy was found mostly with the POS+AB combination. All AZO+ECH combinations except POS+CAS were synergistic against all Candida strains although with variable magnitude; significant antagonism was found for the POS+MIF combination against C. albicans. The AZO+AZO combination was additive for all strains except for a C. parapsilosis strain for which antagonism was also observed. The ECH+ECH combinations were synergistic for all Candida strains except C. glabrata for which they were additive; no antagonism was found.