Alcohol ethoxylates mediate their bacteriostatic effect by altering the cell membrane of Escherichia coli NCTC 8196

Binary mixtures of alcohol ethoxylates, nonylphenol ethoxylates and pesticides exhibit comparative bioactivity against three pests and toxicological risks to aquatic organisms

Nonylphenol ethoxylates are widely used surfactants in the industry and agriculture. However, seeking for alternatives has been imperative considering their effects of the hormonal and other toxicological risks. In the current study, the synergistic effects of nonylphenol ethoxylates or alcohol ethoxylates on the bioactivity of indoxacarb and acetamiprid were compared. Results showed that synergistic ratios of nonylphenol ethoxylates (TX-7∼TX-30) and alcohol ethoxylates (MOA-5∼MOA-20) against Spodoptera exigua, Agrotis ipsilon and Aphis citricola decreased with the EO (ethylene oxide) numbers, although different magnitudes of decreases were observed. Single toxicities of all ethoxylates to Daphnia magna and Brachydanio rerio also dramatically decreased with the EO numbers. In terms of joint toxicity, the combined effects of all ethoxylates and pesticides upon D. magna turned from synergism to antagonism with the increasing EO numbers; the combined effects of nonylphenol ethoxylates and pesticides turned from synergism to antagonism with the increasing EO numbers of ethoxylates, whereas alcohol ethoxylates and pesticides always showed antagonistic effects whatever EO numbers. Overall, alcohol ethoxylates may be potential alternatives for nonylphenol ethoxylates as they exhibited nearly comparative bioactivity against tested pests and toxicities to D. magna and B. rerio.

Formulation of Biocides Increases Antimicrobial Potency and Mitigates the Enrichment of Nonsusceptible Bacteria in Multispecies Biofilms

The current investigation aimed to generate data to inform the development of risk assessments of biocide usage. Stabilized domestic drain biofilm microcosms were exposed daily over 6 months to increasing concentrations (0.01% to 1%) of the biocide benzalkonium chloride (BAC) in a simple aqueous solution (BAC-s) or in a complex formulation (BAC-f) representative of a domestic cleaning agent. Biofilms were analyzed by culture, differentiating by bacterial functional group and by BAC or antibiotic susceptibility. Bacterial isolates were identified by 16S rRNA sequencing, and changes in biofilm composition were assessed by high-throughput sequencing. Exposure to BAC-f resulted in significantly larger reductions in levels of viable bacteria than exposure to BAC-s, while bacterial diversity greatly decreased during exposure to both BAC-s and BAC-f, as evidenced by sequencing and viable counts. Increases in the abundance of bacteria exhibiting reduced antibiotic or BAC susceptibility following exposure to BAC at 0.1% were significantly greater for BAC-s than BAC-f. Bacteria with reduced BAC and antibiotic susceptibility were generally suppressed by higher BAC concentrations, and formulation significantly enhanced this effect. Significant decreases in the antimicrobial susceptibility of bacteria isolated from the systems before and after long-term BAC exposure were not detected. In summary, dose-dependent suppression of bacterial viability by BAC was enhanced by formulation. Biocide exposure decreased bacterial diversity and transiently enriched populations of organisms with lower antimicrobial susceptibility, and the effects were subsequently suppressed by exposure to 1% BAC-f, the concentration most closely reflecting deployment in formulated products.IMPORTANCE Assessment of the risks of biocide use has been based mainly on the exposure of axenic cultures of bacteria to biocides in simple aqueous solutions. The current investigation aimed to assess the effects of formulation on the outcome of biocide exposure in multispecies biofilms. Formulation of the cationic biocide BAC significantly increased antimicrobial potency. Bacteria with lower antimicrobial susceptibility whose populations were enriched after low-level biocide exposure were more effectively suppressed by the biocide at in-use concentrations (1% [wt/vol]) in a formulation than in a simple aqueous solution. These observations underline the importance of simulating normal deployment conditions in considering the risks and benefits of biocide use.

Interactions between cyclodextrins and cellular components: Towards greener medical applications?

In the field of host-guest chemistry, some of the most widely used hosts are probably cyclodextrins (CDs). As CDs are able to increase the water solubility of numerous drugs by inclusion into their hydrophobic cavity, they have been widespread used to develop numerous pharmaceutical formulations. Nevertheless, CDs are also able to interact with endogenous substances that originate from an organism, tissue or cell. These interactions can be useful for a vast array of topics including cholesterol manipulation, treatment of Alzheimer's disease, control of pathogens, etc. In addition, the use of natural CDs offers the great advantage of avoiding or reducing the use of common petroleum-sourced drugs. In this paper, the general features and applications of CDs have been reviewed as well as their interactions with isolated biomolecules leading to the formation of inclusion or exclusion complexes. Finally, some potential medical applications are highlighted throughout several examples.

Aqueous solutions of didecyldimethylammonium chloride and octaethylene glycol monododecyl ether: Toward synergistic formulations against enveloped viruses

Micellization of di-n-decyldimethylammonium chloride, [DiC10][Cl], and octaethylene glycol monododecyl ether, C12E8, mixtures have been investigated by surface tension and conductivity measurements. From these results, various physicochemical and thermodynamic key parameters (e.g. micellar mole fraction of [DiC10][Cl], interaction parameter, free energy of micellization, etc.) have been evaluated and discussed in detail. The results prove high synergistic effect between the two surfactants. Based on these results, the virucidal activity of an equimolar mixture of [DiC10][Cl] and C12E8 has been investigated. A marked synergism was observed on lipid-containing deoxyribonucleic and ribonucleic acid viruses, such as herpes virus, respiratory syncytial virus, and vaccinia viruses. In contrast, Coxsackievirus (non-enveloped virus) was not inactivated. These results support that the mechanism is based on the extraction of lipids and/or proteins from the envelope inside the mixed micelles. This extraction creates "holes" the size of which increases with concentration up to a specific value which triggers the virus inactivation. Such a mixture could be used to extend the spectrum of virucidal activity of the amphiphiles virucides commonly employed in numerous disinfectant solutions.

Effects of Formulation on Microbicide Potency and Mitigation of the Development of Bacterial Insusceptibility

Risk assessments of the potential for microbicides to select for reduced bacterial susceptibility have been based largely on data generated through the exposure of bacteria to microbicides in aqueous solution. Since microbicides are normally formulated with multiple excipients, we have investigated the effect of formulation on antimicrobial activity and the induction of bacterial insusceptibility. We tested 8 species of bacteria (7 genera) before and after repeated exposure (14 passages), using a previously validated gradient plating system, for their susceptibilities to the microbicides benzalkonium chloride, benzisothiozolinone, chlorhexidine, didecyldimethyl ammonium chloride, DMDM-hydantoin, polyhexamethylene biguanide, thymol, and triclosan in aqueous solution (nonformulated) and in formulation with excipients often deployed in consumer products. Susceptibilities were also assessed following an additional 14 passages without microbicide to determine the stability of any susceptibility changes. MICs and minimum bactericidal concentrations (MBC) were on average 11-fold lower for formulated microbicides than for nonformulated microbicides. After exposure to the antimicrobial compounds, of 72 combinations of microbicide and bacterium there were 19≥4-fold (mean, 8-fold) increases in MIC for nonformulated and 8≥4-fold (mean, 2-fold) increases in MIC for formulated microbicides. Furthermore, there were 20≥4-fold increases in MBC (mean, 8-fold) for nonformulated and 10≥4-fold (mean, 2-fold) increases in MBC for formulated microbicides. Susceptibility decreases fully or partially reverted back to preexposure values for 49% of MICs and 72% of MBCs after further passage. In summary, formulated microbicides exhibited greater antibacterial potency than unformulated actives and susceptibility decreases after repeated exposure were lower in frequency and extent.

Antibacterial effects and action modes of asiatic acid

In this study, the antibacterial effects and action modes of asiatic acid against the foodborne bacterial pathogens Escherichia coli O157:H7, Salmonella Typhimurium DT104, Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus, Enterococcus faecalis, and Bacillus cereus were examined. Minimal inhibitory concentrations (MICs) of asiatic acid against these bacteria were in the range of 20-40 μg/mL. Minimum bactericidal concentrations of asiatic acid were in the range of 32-52 μg/mL. Asiatic acid at 2X MIC effectively reduced bacterial numbers from 6 log10 to < 2 log10 in all test bacteria within 6 h (P < 0.05). The antibacterial activity of asiatic acid was not affected by heat treatments from 25 to 100°C. Asiatic acid at 1 or 2X MICs caused 40-56% and 71-89% membrane damage in test bacteria within 2 h, respectively In addition, asiatic acid at 1 or 2X MICs led to 1.5-2.4 ppm and 2.9-4.1 ppm K(+) release within 2 hr, respectively. Asiatic acid treatments dose-dependently increased bacterial nucleotide leakage (P < 0.05). After 3 days of storage at 25°C, the addition of asiatic acid dose-dependently inhibited the growth of test bacteria in ground beef (P < 0.05), in which 8 mg asiatic acid treatments led to bacterial levels (log CFU/g) in said ground beef lower than 2. These findings suggest that asiatic acid might be a potent antibacterial agent to prevent food contamination.

Synthesis and Antibacterial Activity of Alkylated Diamines and Amphiphilic Amides of Quinic Acid Derivatives

Different series of N-alkylated diamines and their derivatives condensed to quinic acid were synthesized and tested for antibacterial properties against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Mycobacterium tuberculosis. The lipophilic chain and carbohydrate moiety modulate the antibacterial activity and the compounds showed a structure-activity relationship. Overall, 11 compounds displayed better activity than chloramphenicol against Gram-positive and Gram-negative bacteria. Monoalkylated amines 2a-h displayed an activity similar to that of ethambutol against Mycobacterium tuberculosis.

Relationship between structure and antibacterial activity of lipophilic N-acyldiamines

We report in this work the preparation and antibacterial evaluation of a series of N-monoacylated diamines against six Gram-positive and 11 Gram-negative bacteria. The results obtained showed the existence of relationship between lipophilicity and antibacterial activity of the tested compounds. The best results were obtained against Gram-positive bacteria for compounds having a 10-12 carbons alkyl chain. Compound 4e was the most active against Microccus lentus (MIC=2 microg/mL), Staphylococcus aureus ATCC 29213 (MIC=4 microg/mL) and Enterobacter aerogenes CDC 1680 (MIC=8 microg/mL).

Investigation into the effect of detergents on disinfectant susceptibility of attached Escherichia coli and Listeria monocytogenes

AIMS

Investigate the effect of detergent treatment on susceptibility of attached Escherichia coli and Listeria monocytogenes to subsequent disinfectant treatment.

METHODS AND RESULTS

Plate counts show that E. coli attached to stainless steel surfaces became significantly more susceptible to benzalkonium chloride (BAC) after treatment with sodium alkyl sulfate (SAS) and fatty alcohol ethoxylate (FAE). No change in susceptibility was observed with Sodium dodecyl sulfate (SDS). L. monocytogenes became significantly less susceptible to BAC after treatment with SAS and SDS yet no change in susceptibility was observed with FAE. Flow cytometry using the fluoresceine propidium iodide revealed significant increases in cell membrane permeability of both organisms by SAS and FAE, although the effect was much greater in E. coli. No change was observed with SDS. Hydrophobic interaction chromatography showed that both organisms became less hydrophobic following treatment with SAS and SDS but FAE had no effect.

CONCLUSIONS

In E. coli, detergents that increase susceptibility to BAC increase membrane permeability. In L. monocytogenes, detergents that reduce susceptibility to BAC lower cell surface hydrophobicity.

SIGNIFICANCE AND IMPACT OF THE STUDY

Detergents can influence the sensitivity of pathogenic food borne micro-organisms to BAC.