Effects of parabens and isothiazolinone on the microbiological quality of baby shampoo: the challenge test

Genetic validation of Aspergillus fumigatus phosphoglucomutase as a viable therapeutic target in invasive aspergillosis

Aspergillus fumigatus is the causative agent of invasive aspergillosis, an infection with mortality rates of up to 50%. The glucan-rich cell wall of A. fumigatus is a protective structure that is absent from human cells and is a potential target for antifungal treatments. Glucan is synthesized from the donor uridine diphosphate glucose, with the conversion of glucose-6-phosphate to glucose-1-phosphate by the enzyme phosphoglucomutase (PGM) representing a key step in its biosynthesis. Here, we explore the possibility of selectively targeting A. fumigatus PGM (AfPGM) as an antifungal treatment strategy. Using a promoter replacement strategy, we constructed a conditional pgm mutant and revealed that pgm is required for A. fumigatus growth and cell wall integrity. In addition, using a fragment screen, we identified the thiol-reactive compound isothiazolone fragment of PGM as targeting a cysteine residue not conserved in the human ortholog. Furthermore, through scaffold exploration, we synthesized a para-aryl derivative (ISFP10) and demonstrated that it inhibits AfPGM with an IC50 of 2 μM and exhibits 50-fold selectivity over the human enzyme. Taken together, our data provide genetic validation of PGM as a therapeutic target and suggest new avenues for inhibiting AfPGM using covalent inhibitors that could serve as tools for chemical validation.

Controversy around parabens: Alternative strategies for preservative use in cosmetics and personal care products

Parabens usage as preservatives in cosmetics and personal care products have been debated among scientists and consumers. Parabens are easy to production, effective and cheap, but its safety status remains controversial. Other popular cosmetics preservatives are formaldehyde, triclosan, methylisothiazolinone, methylchloroisothiazolinone, phenoxyethanol, benzyl alcohol and sodium benzoate. Although their high antimicrobial effectiveness, they also exhibit some adverse health effects. Lately, scientists have shown that natural substances such as essential oils and plant extracts present antimicrobial potential. However, their use in cosmetic is a challenge. The present review article is a comprehensive summary of the available methods to prevent microbial contamination of cosmetics and personal care products, which can allow reducing the use of parabens in these products.

Microorganisms populating the water-related indoor biome

Modernisation of our households created novel opportunities for microbial growth and thus changed the array of microorganisms we come in contact with. While many studies have investigated microorganisms in the air and dust, tap water, another major input of microbial propagules, has received far less attention. The quality of drinking water in developed world is strictly regulated to prevent immediate danger to human health. However, fungi, algae, protists and bacteria of less immediate concern are usually not screened for. These organisms can thus use water as a vector of transmission into the households, especially if they are resistant to various water treatment procedures. Good tolerance of unfavourable abiotic conditions is also important for survival once microbes enter the household. Limitation of water availability, high or low temperatures, application of antimicrobial chemicals and other measures are taken to prevent indoor microbial overgrowth. These conditions, together with a large number of novel chemicals in our homes, shape the diversity and abundance of indoor microbiota through constant selection of the most resilient species, resulting in a substantial overlap in diversity of indoor and natural extreme environments. At least in fungi, extremotolerance has been linked to human pathogenicity, explaining why many species found in novel indoor habitats (such as dishwasher) are notable opportunistic pathogens. As a result, microorganisms that often enter our households with water and are then enriched in novel indoor habitats might have a hitherto underestimated impact on the well-being of the increasingly indoor-bound human population. KEY POINTS: Domestic environment harbours a large diversity of microorganisms. Microbiota of water-related indoor habitats mainly originates from tap water. Bathrooms, kitchens and household appliances select for polyextremotolerant species. Many household-related microorganisms are human opportunistic pathogens.

Antibacterial Effects of Schisandra chinensis Extract on Escherichia coli and its Applications in Cosmetic

Schisandra chinensis (Turcz.) Baill (S. chinensis), an edible traditional medicine herb, has a strong constitution, which extract has good antibacterial activity. The study investigated its antibacterial properties on E. coli, to find a candidate for the development as new preservative. In vitro antibacterial assay showed that S. chinensis extract (SCE) effectively inhibited the growth of test bacteria with MBC of 18 mg/mL. In model cosmetic system of O/W emulsions, SCE possessed a great antibacterial capacity. The growth curves of E. coli treated with SCE exhibited an extended lag phase and restricted log phase. Scanning electron microscopy showed that the treated E. coli cells exhibited wrinkled and withered surfaces, and disappearing outmost layer, suggesting S. chinensis extract can damage S. aureus cell member and wall, in addition, the leakage of periplasm enzyme AKPase and the increased activities of Na⁺/K⁺-ATPase and Ca⁺⁺-ATPase in cell membrane were also consistent with the microscopy results. Moreover, the S. chinensis extract can decrease the activities of dehydrogenase and total ATPase and the content of intracellular proteins, and bind with S. aureus DNA by electrostatic and groove binding. The results indicated that SCE might be a candidate cosmetic preservative for its good antibacterial activity and multiple targets on E. coli.

Isothiazolinones Quantification in Shampoo Matrices: A Matter of Method Optimization or Stability Driven by Interactions?

Methylisothiazolinone (MI) is one of the most used preservatives in shampoos and also one of the most effective. A preservative mixture known as Kathon™ CG is commercially available. It contains 5-chloro-2-methyl-4-isothiazolin-3-one (CMI) and 2-methyl-4-isothiazolin-3-one (MI) (3:1) and stabilizers. The aim of this study is to evaluate the influence of formulation factors in the quantification and stability of isothiazolinones in shampoos. Two shampoo bases containing Kathon™ CG as a preservative were prepared. Some ingredients that are at risk of interfering with the preservative stability were added to these formulations. The preservative was quantified by HPLC-DAD (High-performance liquid chromatography with a diode-array detector) after preparation of the formulation and after storage at room temperature and at 40 °C. The addition of magnesium silicate proved to be essential for the breakdown of the interaction between the matrix and the analytes in the extraction procedure. The content of CMI/MI decreased right after preparation indicating that immediate interactions between CMI/MI and the ingredients may have occurred after preparation resulting in a decrease in the preservative concentration. Detrimental interactions between the ingredients, regarding the stability of the isothiazolinones were detected immediately after preparation and over time resulting in the reduction of CMI/MI concentration in these cosmetic shampoos.

Interaction between Different Pharmaceutical Excipients in Liquid Dosage Forms-Assessment of Cytotoxicity and Antimicrobial Activity

Nowadays, the safety of parabens as pharmaceutical preservatives is debated. Recent studies investigated their interference with the oestrogen receptors, nevertheless their carcinogenic activity was also proved. That was the reason why the re-evaluation of the biocompatibility and antimicrobial activity of parabens is required using modern investigation methods. We aimed to test the cytotoxic, antifungal and antibacterial effect of parabens on Caco-2 cells, C. albicans, C. parapsilosis, C. glabrata, E. coli, P. aeruginosa and S. aureus. Two complex systems (glycerol-Polysorbate 20; ethanol-Capryol PGMC™) were formulated to study-with the MTT-assay and microdilution method, respectively-how other excipients may modify the biocompatibility and antimicrobial effect of parabens. In the case of cytotoxicity, the toxicity of these two systems was highly influenced by co-solvents and surfactants. The fungi and bacteria had significantly different resistance in the formulations and in some cases the excipients could highly modify the effectiveness of parabens both in an agonistic and in a counteractive way. These results indicate that with appropriate selection, non-preservative excipients can contribute to the antimicrobial safety of the products, thus they may decrease the required preservative concentration.

Preservative efficacy of selected antimicrobials of natural origin in a cosmetic emulsion

OBJECTIVE

To investigate the efficacy of 13 antimicrobial substances (11 substances of natural origin and two conventional preservatives as controls) at two concentrations in an o/w cosmetic emulsion.

METHODS

Cosmetic formulations were analysed for total aerobic bacterial count and total combined yeast count according to the European Pharmacopoeia 8.0. Challenge tests were performed according to the ISO 11930 standard.

RESULTS

The total aerobic bacterial count, the total combined yeast count and the total aerobic mesophilic microorganisms were below the acceptable limit for all cosmetic formulations. Challenge test criterion A was fulfilled by all antimicrobials of natural origin, except levulinic acid in the challenge test with Candida albicans, Lactobacillus ferment in the challenge test with C. albicans and Pseudomonas aeruginosa, and grapefruit seed extract in the challenge test with C. albicans. Phenoxyethanol and the combination of methylparaben and propylparaben were inefficient at the minimum studied concentrations.

CONCLUSION

The results offer important comparative data on the level of preservative efficacy within the group of antimicrobials of natural origin and in reference to some typical, widely used conventional preservatives. Further research must be encouraged regarding cosmetic over-preservation. This article is protected by copyright. All rights reserved.

Baby Shampoo Versus Povidone-Iodine or Isopropyl Alcohol in Reducing Eyelid Skin Bacterial Load

PURPOSE

Baby shampoo is used as an alternative surgical skin preparation, but the evidence supporting its use is scarce with no descriptions of efficacy in the periocular region. The authors compare the efficacy of baby shampoo, povidone-iodine (PI, Betadine) and isopropyl alcohol (IA) in reducing eyelid skin bacterial load.

METHODS

Prospective, randomized, comparative, and interventional trial. Bacterial load on adult, human eyelid skin was quantitated before and after cleansing with 1) dilute baby shampoo, 2) 10% PI, or 3) 70% IA. Paired skin swabs were collected from a 1 cm area of the upper eyelid of subjects before and after a standardized surgical scrub technique. Samples were cultured on 5% sheep blood agar for 24 hours. The number of colony forming units (CFU) was assessed and bacterial load per square centimeter of eyelid skin was quantified.

RESULTS

Baseline and postcleansing samples were assessed from 42 eyelids of 42 subjects (n = 14 for each of baby shampoo, PI, and IA). Before cleansing, similar amounts of bacterial flora were grown from all specimens (median log CFU/cm = 2.04 before baby shampoo, 2.01 before PI, 2.11 before IA; p > 0.05). All 3 cleansing agents significantly reduced the bacterial load (p < 0.01 for each). There was no statistically significant difference in postcleansing bacterial load between the 3 cleansing agents (median log CFU/cm = 0.48 after baby shampoo, 0.39 after PI, 0.59 after IA; p > 0.05). Change from baseline in bacterial load was statistically similar for all 3 agents (median reduction in log CFU/cm = 1.28 with baby shampoo, 1.57 with PI, 1.40 with IA; p > 0.05). These corresponded to bacterial load reductions of 96.3%, 96.6%, and 98.4% for baby shampoo, PI, and IA, respectively.

CONCLUSIONS

Baby shampoo achieved comparable diminution in eyelid skin bacterial load to PI or IA. These data suggest baby shampoo may be an effective preoperative cleansing agent.

Using thermal desorption electrospray ionization mass spectrometry to rapidly determine antimicrobial preservatives in cosmetics

RATIONALE

Characterization and quantification of permitted preservatives are important inspections to prevent the overuse of preservatives in authentic formulations. However, the complexity of sample matrices makes preservative determination in cosmetics a tedious process. A rapid analytical strategy to identify preservatives would insure large numbers of products are in compliance with government regulations.

METHODS

Thermal desorption electrospray ionization mass spectrometry (TD-ESI-MS) was used to directly detect preservative compounds in authentic formulations without sample pretreatment. The technique employs a metal probe, which was configured for sampling cosmetics in their original states and was inserted in a closed preheated oven to thermally desorb analytes. The desorbed analytes were then carried by a nitrogen gas stream into an ESI plume, where the formed ions were subsequently detected by the mass analyzer.

RESULTS

The TD-ESI mass and tandem mass spectra of different classes of preservative standards were rapidly obtained, and the limits of detection were far below the legal limit of their respective concentrations. The preservatives were also directly detected in different types of authentic formulations in the absence of sample preparation, and within a few seconds per sample. Calibration curves for preservatives in four common formulations yielded good linearity in the regulation-allowed range.

CONCLUSIONS

Due to its sensitivity, short analysis time, repeatability, and quantitative ability, TD-ESI-MS may serve as a suitable tool for large-scale screening of cosmetic preservatives to assure product safety. Copyright © 2016 John Wiley & Sons, Ltd.

Tissue accumulation and toxicity of isothiazolinone in Ctenopharyngodon idellus (grass carp): association with P-glycoprotein expression and location within tissues

Isothiazolinone is widely used as a broad-spectrum fungicide in various industries, such as oil, paper, pesticide, dyes, tanning and cosmetics. There is an increasing concern over protection of the aquatic environment due to its large-scale use. The acute toxicity (LC50) of isothiazolinone in Ctenopharyngodon idellus was investigated. The residual time and accumulation in tissues, P-glycoprotein mRNA level and localization of P-glycoprotein in the liver and kidney were also analyzed. The LC50 (48 h) values of isothiazolinone to C. idellus were 0.53±0.17 mg/L and 0.41±0.08 mg/L at 15 °C and 25 °C, respectively. The LC50 values decreased as the temperature increased. The accumulation of isothiazolinone in livers and kidneys in the high temperature group (25 °C) was significantly greater than that of the low temperature group (15 °C). Prolonged tissue residual time of isothiazolinone was seen in all the groups. There were significant differences in P-glycoprotein mRNA expression between isothiazolinone-treated groups and control samples (P<0.05-0.01). Temperature affected accumulation and toxicity of isothiazolinone.