Evaluation of antimicrobial persistent activity of alcohol-based hand antiseptics against bacterial contamination

Mechanism of antibacterial property of micro scale rough surface formed by fine-particle bombarding

Fine-particle bombardment (FPB) is typically used to modify metal surfaces by bombarding them with fine particles at high speed. FPB is not a coating technique but is used for forming microscale concavities and convexities on a surface. Previously, we reported that an FPB-treated surface showed antibacterial effects; however, the underlying mechanisms remain unclear. We hypothesized that the pitch size of concavity and convexity, and irregular microscale pattern of FPB-treated surfaces might contribute to the antibacterial performance. In this study, we applied FPB to stainless-steel surfaces and evaluated the antibacterial effects of the FPB-treated surfaces based on ISO 22,196:2007. The FPB-treated surfaces exhibited antibacterial activity against Escherichia coli, with an antibacterial activity value (R) of two or more. Furthermore, our experiments suggest that the antibacterial mechanism of the FPB-treated surface can be attributed to increased oxidative stress in bacteria owing to physical stress from the rough surface. The antibacterial effect of FPB-treated surfaces offers an effective measure against drug-resistant bacteria.

Comparing the antibacterial efficacy and functionality of different commercial alcohol-based sanitizers

The use of alcohol-based sanitizers has been recommended as an effective alternative to clean hands, especially in the case when hand washing is not doable. This is especially critical with the COVID-19 pandemic, where personal hygiene is an important factor to deter the spread of the virus. This study assesses and evaluates the differences in antibacterial efficacy and functionalities of five different commercial alcohol-based sanitizers with different formulations. All sanitizers were able to provide instant sanitization functionality, effectively killing 5x105 CFU/mL of inoculated bacteria. However, comparing pure alcohol-based sanitizers against alcohol-based sanitizers with a secondary active ingredient demonstrated that the addition of a secondary active ingredient enhanced the effectiveness and functionalities of the sanitizers. Alcohol-based sanitizers with secondary active ingredients demonstrated a more rapid antimicrobial mode of action, eradicating all 106 CFU/mL of bacteria within 15 seconds of contact, in contrast to the 30 min for purely alcohol-based sanitizers. The secondary active ingredient also provided additional anti-biofilm functionality to prevent opportunistic microbes from attaching and proliferating on the treated surface, leading to serious biofilm formation. On top of that, treatment of surfaces with alcohol-based sanitizers with secondary active ingredients also imparted prolonged antimicrobial protection to the surface lasting up to 24 h. On the other hand, purely alcohol-based sanitizers do not seem to possess such quality with the treated surface being vulnerable to microbial contamination within minutes after application. These results highlighted the benefits of adding a secondary active ingredient in sanitizer formulation. However, care needs to be taken to evaluate the type and concentration of antimicrobial agents chosen as the secondary active ingredient.

Longevity of hand sanitisers on fingers

CLINICAL RELEVANCE

Hand hygiene is important to reduce the spread of microbes in clinical settings. Hand sanitisers that last longer may be beneficial.

BACKGROUND

Longevity of hand sanitisation products on fingers and hands may be important to help reduce microbial transmission. The current study evaluated the persistence of disinfection of three hand sanitisers.

METHODS

Initially the minimum inhibitory concentrations of the hand sanitisers were determined using strains of Staphylococcus epidermidis and S. aureus. Then a cross-over study with participants randomly assigned to use three different hand sanitisers for 30 seconds was undertaken. The number of bacteria and fungi on fingers was assessed 10 and 20 minutes and 4 hours after use. The type of microbial inhibition of the capric acid sanitiser was studied by examining the effects of adding Tween 80 and lecithin to microbial agar.

RESULTS

The minimum inhibitory concentration of an alcohol-based sanitiser (AS) was 10%, for the capric acid-based (CS) sanitiser was 70%, and for the quaternary ammonium-based (QS) sanitiser was < 10%. AS significantly reduced the number of microbes on fingers 10 minutes after hand washing (18.2 cfu/mL) compared to CS (59.7 cfu/mL; p < 0.0001) or QS (64.5 cfu/mL; p < 0.0001). Twenty minutes after use, microbes on fingers after AS (23 cfu/mL) or CS (16.7 cfu/mL) were significantly reduced compared to QS (72.2  cfu/mL; p < 0.0001) and the numbers on fingers after CS was significantly less than after AS (p = 0.002). Four hours after use of any hand sanitiser, the number of microbes increased to near baseline levels. The reduction in bacterial numbers was not affected by the use of neutralisers in agar (48 ± 28% reduction with, 47 ± 49% reduction without; p = 0.876).

CONCLUSIONS

Hand sanitisers containing capric acid or alcohol out-performed one containing quaternary ammonium in the clinical trial and may help reduce the spread of microbes.

Antibacterial effect on microscale rough surface formed by fine particle bombarding

Fine particle bombarding (FPB) is typically utilized to modify metal surfaces by bombarding them with fine particles at high-speed. The diameters of the particles range from several to tens of micrometers. FPB forms fine microscale concavities and convexities on a surface. As FPB-treated surfaces are widely used in the food industry, the influence of bacteria on their surface must be considered. In this study, we examined the antibacterial activity of microscale rough surfaces formed by FPB. We applied FPB to a stainless-steel surface and evaluated the antibacterial effect of FPB-treated surfaces based on JIS Z 2801 (a modified test method from ISO 22196:2007). Our results indicated that the FPB-treated surfaces (FPB-1 (avg. pitch: 0.72 µm) and FPB-2 (avg. pitch: 3.56 µm)) exhibited antibacterial activity both against Escherichia coli and Staphylococcus aureus.

Pre-surgical hand preparation in veterinary practice

The objective of this paper is to review the evidence for different methods of surgical hand preparation applicable to veterinary practice. Surgical hand preparation is an essential step in performing surgery as a veterinarian. Recommended protocols and products for surgical hand preparation have varied since its inception in the late 1800s. Many factors must be considered when assessing the efficacy, safety, and users' compliance with any available product. Traditional scrub methods employing chlorhexidine gluconate or povidone-iodine have been compared to alcohol-based rub protocols with respect to immediate and prolonged efficacy, safety, compliance, requirements for theatre furniture, cost and water usage. Although much of the comparative data has been generated in human medical facilities, extrapolation of the data to veterinary surgery is appropriate. Considerations for veterinary practice are specifically discussed. Overall, the benefits of alcohol-based rubs indicate that this should be the preferred method of pre-surgical hand preparation for veterinarians in all types of practice.

Surgical hand preparation in an equine hospital: Comparison of general practice with a standardised protocol and characterisation of the methicillin-resistant Staphylococcus aureus recovered

Presurgical hand asepsis is part of the daily routine in veterinary medicine. Nevertheless, basic knowledge seems to be low, even among specialised veterinary surgeons. The major objectives of our study were to assess current habits for presurgical hand preparation (phase 1) among personnel in a veterinary hospital and their effectiveness in reducing bacteria from hands in comparison to a standardised protocol (phase 2). Assessment of individual habits focused on time for hand washing and disinfection, the amount of disinfectant used, and the usage of brushes. The standardised protocol defined hand washing for 1 min with liquid neutral soap without brushing and disinfection for 3 min. All participants (2 surgeons, 8 clinic members, 32 students) used Sterillium®. Total bacterial counts were determined before and after hand washing, after disinfection, and after surgery. Hands were immersed in 100 ml sterile sampling fluid for 1 min and samples were inoculated onto Columbia sheep blood agar using the spread-plate method. Bacterial colonies were manually counted. Glove perforation test was carried out at the end of the surgical procedure. Differences in the reduction of relative bacterial numbers between current habits and the standardised protocol were investigated using Mann-Whitney-Test. The relative increase in bacterial numbers as a function of operation time (≤60 min, >60 min) and glove perforation as well as the interaction of both was investigated by using ANOVA. Forty-six and 41 preparations were carried out during phase 1 and phase 2, respectively. Individual habits differed distinctly with regard to time (up to 8 min) and amount of disinfectant (up to 48 ml) used both between participants and between various applications of a respective participant. Comparison of current habits and the standardised protocol revealed that the duration of hand washing had no significant effect on reducing bacteria. Contrary, the reduction in bacterial numbers after disinfection by the standardised protocol was significantly higher (p<0.001) compared to routine every-day practice. With regard to disinfection efficacy, the standardised protocol completely eliminated individual effects. The mean reduction in phase 1 was 90.72% (LR = 3.23; right hand) and 89.97% (LR = 3.28; left hand) compared to 98.85% (LR = 3.29; right hand) and 98.92% (LR = 3.47; left hand) in phase 2. Eight participants (19%) carried MRSA (spa type t011, CC398) which is well established as a nosocomial pathogen in veterinary clinics. The isolates could further be assigned to a subpopulation which is particularly associated with equine clinics (mainly t011, ST398, gentamicin-resistant). Glove perforation occurred in 54% (surgeons) and 17% (assistants) of gloves, respectively, with a higher number in long-term invasive procedures. Overall, bacterial numbers on hands mainly increased over time, especially when glove perforation occurred. This was most distinct for glove perforations on the left hand and with longer operating times. Our results demonstrate that standardised protocols highly improve the efficacy of hand asepsis measures. Hence, guiding standardised protocols should be prerequisite to ensure state-of-the-art techniques which is essential for a successful infection control intervention.

Antiseptic Agents Elicit Short-Term, Personalized, and Body Site-Specific Shifts in Resident Skin Bacterial Communities

Despite critical functions in cutaneous health and disease, it is unclear how resident skin microbial communities are altered by topical antimicrobial interventions commonly used in personal and clinical settings. Here we show that acute exposure to antiseptic treatments elicits rapid but short-term depletion of microbial community diversity and membership. Thirteen subjects were enrolled in a longitudinal treatment study to analyze the effects of topical treatments (i.e., ethanol, povidone-iodine, chlorhexidine, and water) on the skin microbiome at two skin sites of disparate microenvironment: forearm and back. Treatment effects were highly dependent on personalized and body site-specific colonization signatures, which concealed community dynamics at the population level when not accounted for in this analysis. The magnitude of disruption was influenced by the identity and abundance of particular bacterial inhabitants. Lowly abundant members of the skin microbiota were more likely to be displaced, and subsequently replaced, by the most abundant taxa prior to treatment. Members of the skin commensal family Propionibactericeae were particularly resilient to treatment, suggesting a distinct competitive advantage in the face of disturbance. These results provide insight into the stability and resilience of the skin microbiome, while establishing the impact of topical antiseptic treatment on skin bacterial dynamics and community ecology.