Colorimetric detection of residual quaternary ammonium compounds on dry surfaces and prediction of antimicrobial activity using bromophenol blue

The antibacterial performance of a residual disinfectant against Staphylococcus aureus on environmental surfaces

Environmental surfaces play a key role in transmitting pathogens that can survive on surfaces for long durations. The interest in long-lasting or residual disinfectants are, therefore, growing as it might protect surfaces for longer than traditional disinfectants. In this study, a quat-based product claiming residual disinfecting performance against bacteria, among other microorganisms, was tested using an approved standardized method, in a controlled laboratory study and on environmental surfaces in an office building. The results obtained showed that the residual disinfectant can reduce the bacterial counts significantly compared to a traditional quat-based disinfectant when used on horizontal surfaces, twenty-four hours after application. During the standardized test method, the residual disinfectant provided a 6-log reduction, whereas the traditional disinfectant provided only a 1.9-log reduction. Similarly, the residual disinfectant provided a 2.5 log reduction in the laboratory study, whereas the traditional disinfectant had too-numerous-to-count colonies. When tested on environmental surfaces, an ANOVA statistical analysis indicated that surfaces treated with the residual disinfectant had significantly less bacteria present twenty-four hours after application. The antibacterial performance of the residual disinfectant showed to be limited by the orientation of the treated surface, and the thickness of the product film dried on the surface. This study showed the potential of residual disinfectants that warrants further investigation and could potentially aid the further development of the technology.

Evaluation of Quatsome Morphology, Composition, and Stability for Pseudomonas aeruginosa Biofilm Eradication

Biofilm infections are a major cause of food poisoning and hospital-acquired infections. Quaternary ammonium compounds are a group of effective disinfectants widely used in industry and households, yet their efficacy is lessened when used as antibiofilm agents compared to that against planktonic bacteria. It is therefore necessary to identify alternative formulations of quaternary ammonium compounds to achieve an effective biofilm dispersal. Quaternary ammonium amphiphiles can form vesicular structures termed "quatsomes" in the presence of cholesterol. In addition to their intrinsic antimicrobial properties, quatsomes can also be used for the delivery of other types of antibiotics or biomarkers. In this study, quatsomes were prepared from binary mixtures of cholesterol and mono- or dialkyl-quaternary ammonium compounds; then, the integrity and stability of their vesicular structure were assessed and related to monomer chain number and chain length. The quatsomes were used to treat Pseudomonas aeruginosa biofilms, showing effective antibiofilm abilities comparable to those of their monomers. A systematic liquid chromatography-mass spectrometry method for quantifying quatsome vesicle components was also developed and used to establish the significance of cholesterol in the quatsome self-assembly processes.

Continuous surface and air decontamination technologies: Current concepts and controversies

Effective and safe continuous surface and air decontamination technologies could be a useful adjunct to routine cleaning and disinfection in health care settings. Continuously active quaternary ammonium disinfectants that provide residual antimicrobial activity on undisturbed surfaces for up to 24.ßhours have been shown to reduce the recovery of clinically important pathogens in some but not all real-world studies. Although quaternary ammonium-based supplemental coatings have been reported to provide prolonged residual efficacy in patient care settings, there is concern that some of these products may be removed by routine cleaning and disinfection. To address this concern, the Environmental Protection Agency has recently issued updated guidance requiring demonstration of efficacy after multiple abrasion and chemical exposures for registration of supplemental residual antimicrobial coatings. Far-ultraviolet-C and direct irradiation below exposure limits are promising technologies for continuous air and surface decontamination in occupied spaces, but additional studies are needed to evaluate their long-term safety and efficacy. Given the increasing use of electronic air cleaning technologies in community and health care settings, there is a need for studies to assess real-world efficacy and safety.

Physical mechanisms driving the reversible aggregation of Staphylococcus aureus and response to antimicrobials

Formation of non-sessile, auto-aggregated cells of Staphylococcus aureus contributes to surface colonization and biofilm formation, hence play a major role in the early establishment of infection and in tolerance to antimicrobials. Understanding the mechanism of aggregation and the impact of aggregation on the activity of antimicrobials is crucial in achieving a better control of this important pathogen. Previously linked to biological phenomena, physical interactions leading to S. aureus cellular aggregation and its protective features against antimicrobials remain unraveled. Herein, in-vitro experiments coupled with XDLVO simulations reveal that suspensions of S. aureus cells exhibit rapid, reversible aggregation (> 70%) in part controlled by the interplay between cellular hydrophobicity, surface potential and extracellular proteins. Changing pH and salt concentration in the extracellular media modulated the cellular surface potential but not the hydrophobicity which remained consistent despite these variations. A decrease in net cellular negative surface potential achieved by decreasing pH or increasing salt concentrations, caused attractive forces such as the hydrophobic and cell–protein interactions to prevail, favoring immediate aggregation. The aggregation significantly increased the tolerance of S. aureus cells to quaternary ammonium compounds (QAC). The well-dispersed cell population was completely inactivated within 30 s whereas its aggregated counterpart required more than 10 min.