Benzethonium Chloride

The oral cavity hosts numerous bacteria that are associated with various systemic diseases. The Oral Bacteria Counter (PHC Corporation, Tokyo, Japan), a microorganism quantitative analyzer that utilizes dielectrophoretic impedance measurements, enables rapid bacterial counting and is widely used in dental practice in Japan. However, it may also detect nonviable bacteria. This study aimed to assess the impact of disinfectants, electrolytes, and viscosity on the accuracy of the Oral Bacteria Counter and to determine whether it measures non-viable bacteria similarly to viable bacteria.

To evaluate the effect of the disinfectants, samples of 7% povidone-iodine (PV-I), 0.2% benzethonium chloride, 5% chlorhexidine (CHX), 0.2% CHX, 0.05% CHX, sterile water, and saline were measured using the Oral Bacteria Counter. The effect of viscosity was assessed by mixing sterile water with glycerol in various ratios and measuring the dielectrophoretic impedance of the bacterial counts at different viscosities. For the electrolyte effects, samples of Staphylococcus aureus diluted in sterile water or saline were measured using the Oral Bacteria Counter. Additionally, samples of 7% PV-I or 5% CHX diluted in sterile water or saline were measured. Bacterial counts were then measured and compared using the Oral Bacteria Counter, our developed delayed real-time polymerase chain reaction (DR-PCR) method (which quantifies only viable bacteria), and culture methods.

Disinfectants such as 5% CHX and 7% PV-I produced high readings on the Oral Bacteria Counter, even when no viable bacteria were present. Higher glycerol concentrations, which increased the viscosity, resulted in lower bacterial counts. The presence of electrolytes, particularly saline, led to higher readings on the Oral Bacteria Counter, which detected both viable and non-viable bacteria, whereas DR-PCR and culture methods did not detect non-viable bacteria.

The Oral Bacteria Counter may be influenced by disinfectants, viscosity, and electrolytes, leading to potential inaccuracies in bacterial quantification. For accurate bacterial measurements, it is essential to consider these factors and ideally combine the results from the Oral Bacteria Counter with methods such as DR-PCR for more reliable assessment.

Background It is commonly accepted that microorganisms found within hard-to-heal wounds are present in biofilm form. Biofilms are often polymicrobial in nature, which increases their virulence and tolerance to antimicrobial agents. The aim of this study was to compare the antibiofilm activity of silver-containing antimicrobial wound dressings in a dual-species simulated wound biofilm model. Materials and methods Four silver-containing wound dressings were evaluated in vitro: Aquacel^® Ag+ Extra™ dressing, KerraContact^® Ag dressing, Durafiber* Ag dressing, and UrgoClean Ag dressing. Each dressing was applied to a simulated wound assembly containing biofilm-gauze inoculated with Klebsiella pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA). Each biofilm-inoculated gauze was incubated at 35±3^ºC for 6, 24, 48 and 72 hours. Enumeration of surviving biofilm bacteria at each time point was performed in triplicate for each test dressing and its equivalent control. Results Aquacel^® Ag+ Extra™ dressing was observed to reduce the biofilm population within 24 hours with a >4 log₁₀ kill observed for K. pneumoniae and >6 log₁₀ for MRSA from an initial biofilm challenge of 4.16×10⁹ CFU/mL. This kill rate was sustained for the duration of the challenge period, with Aquacel^® Ag+ Extra™ dressing reducing the biofilm population to non-detectable levels (<30 Colony Forming Units (CFU) per test) by 72 hours for K. pneumoniae and by 48 hours for MRSA. KerraContact^® Ag dressing demonstrated an initial reduction at 6 hours of ~2 log₁₀ in both K. pneumoniae and MRSA. Durafiber* Ag dressing exhibited a slight, gradual reduction in biofilm population over the course of the test period, reducing each challenge organism by ~2.5 log₁₀ by 72 hours. UrgoClean Ag was shown to have little to no impact on the dual-species biofilm with levels remaining similar or greater than that recovered prior to dressing application. The no-dressing biofilm-colonised gauze control demonstrated that the biofilm bacteria remained viable throughout the test period and species population proportionality was maintained. Conclusion Using a dual-species simulated wound biofilm model comprising the pathogens K. pneumoniae and MRSA, Aquacel^® Ag+ Extra™ dressing demonstrated significantly greater antibiofilm activity than the other silver-containing dressings. The enhanced antibiofilm activity of Aquacel^® Ag+ Extra™ dressing in this study may be attributed to the additional antibiofilm agents, ethylenediaminetetraacetic acid and benzethonium chloride, contained within the dressing.