Bactericidal activity of 3 cutaneous/mucosal antiseptic solutions in the presence of interfering substances: Improvement of the NF EN 13727 European Standard?

The application of normative documents for determination of biocidal activity of disinfectants and antiseptics dedicated for medical area: a narrative review

Disinfectants and antiseptics are important weapons to reduce the number of microorganisms and thus to limit the number of infections. Different methods of antimicrobial activity testing, often not standardised, without appropriate controls and not validated are applied. To address these issues, several European Standards (EN) have been developed, describing the test methods to determine whether chemical disinfectants or antiseptic products have appropriate bactericidal, sporicidal, mycobactericidal or tuberculocidal activity; fungicidal or yeasticidal activity; or virucidal activity. In this narrative review, the 17 EN concerning evaluation of the above-mentioned antimicrobial activity of preparations dedicated to the medical area are briefly reviewed, together with recent publications on this topic. Suspension and carrier tests have been performed in clean and dirty conditions simulating the medical area. In addition, a wide range of applications of these standards has been presented in the research of biocides for hand antisepsis, surfaces disinfection, including airborne disinfection as well as medical device and medical textile disinfection. The role of normative documents in the investigation of antimicrobial activity of disinfectants and antiseptics to limit infections has been underestimated. This narrative review aims to persuade researchers to conduct antimicrobial activity testing in line with validated EN and highlights an existing gap in ongoing research. It also aims to raise awareness of the wide range of biocidal activity tests with standardised methods in medical area. We also pay attention to the recently developed European Pharmacopoeia monography concerning the testing of bactericidal and fungicidal activity of antiseptics classified as medicinal products.

Bactericidal and virucidal activity of ethanol and povidone-iodine

Ethanol and povidone‐iodine (PVP‐I) are important microbicides that inactivate bacteria and viruses. The present study provides a review of literature data on the concentration‐dependent bactericidal and virucidal activity of ethanol and PVP‐I in vitro. A systematic search was performed using the meta‐database for biomedicine PubMed. Eventually, 74 studies with original data on the reduction of bacterial and viral infectivity using in vitro tests were analyzed. A safe bactericidal effect of ethanol can be expected at concentrations between 60% and 85%, and the exposure times vary between ≤0.5 and ≥5 min. Within an exposure of up to 5 min, 80%–90% ethanol also exerts virucidal/low‐level activity, which includes its action against enveloped viruses plus adeno‐, noro‐, and rotaviruses. For PVP‐I, the best bactericidal and virucidal/high‐level effect is present at a concentration range of approx. 0.08%–0.9% depending on the free iodine concentration. The maximum exposure times are 5 min for bacteria and 60 min for viruses. The available data may help optimize the significant inactivation of bacteria and viruses in various areas. However, as the conditions in application practice can vary, concrete recommendations for the application can only be derived to a limited extent.

Comparison of bactericidal and fungicidal efficacy of antiseptic formulations according to EN 13727 and EN 13624 standards

Background/aim

In this study, the antibacterial and antifungal properties of the five most commonly used antiseptic formulations were evaluated in terms of different contact times and organic conditions.

Materials and methods

Solutions of chlorhexidine digluconate, povidone iodine, isopropyl alcohol, hydrogen peroxide, and tincture of iodine were prepared and tested according to European standards EN 13727 and EN 13624 with different parameters.

Results

The results showed that isopropyl alcohol (70% v/v) and tincture of iodine (2%) had greater bactericidal and fungicidal activity against the four tested bacteria and two fungi in all conditions.

Conclusion

When the results of the five different active substances were quantitatively evaluated regarding their bactericidal and fungicidal activities, it was found that contact time and organic load significantly affected the antiseptic efficacy.

Herpes simplex virus-1 entrapped in Candida albicans biofilm displays decreased sensitivity to antivirals and UVA1 laser treatment

BACKGROUND

Recently, we published data suggesting a mutualistic relationship between HSV-1 and Candida. albicans; in particular: (a) HSV-1 infected macrophages are inhibited in their anti-Candida effector function and (b) Candida biofilm protects HSV-1 from inactivation. The present in vitro study is aimed at testing the effects of Candida biofilm on HSV-1 sensitivity to pharmacological and physical stress, such as antiviral drugs (acyclovir and foscarnet) and laser UVA1 irradiation. We also investigated whether fungus growth pattern, either sessile or planktonic, influences HSV-1 sensitivity to antivirals.

METHODS

Mature Candida biofilms were exposed to HSV-1 and then irradiated with laser light (UVA1, 355 λ). In another set of experiments, mature Candida biofilm were co-cultured with HSV-1 infected VERO cells in the presence of different concentrations of acyclovir or foscarnet. In both protocols, controls unexposed to laser or drugs were included. The viral yield of treated and untreated samples was evaluated by end-point titration. To evaluate whether this protective effect might occur in relation with a different growth pattern, HSV-1 infected cells were co-cultured with either sessile or planktonic forms of Candida and then assessed for susceptibility to antiviral drugs.

RESULTS

UVA1 irradiation caused a 2 Log reduction of virus yield in the control cultures whereas the reduction was only 1 Log with Candida biofilm, regardless to the laser dose applied to the experimental samples (50 or 100 J/cm²). The presence of biofilm increased the IC₉₀ from 18.4-25.6 J/cm². Acyclovir caused a 2.3 Log reduction of virus yield in the control cultures whereas with Candida biofilm the reduction was only 0.5 Log; foscarnet determined a reduction of 1.4 Log in the controls and 0.2 Log in biofilm cultures. Consequently, the ICs₅₀ for acyclovir and foscarnet increased by 4- and 12-folds, respectively, compared to controls. When HSV-1 was exposed to either sessile or planktonic fungal cells, the antiviral treatments caused approximately the same weak reduction of virus yield.

CONCLUSIONS

These data demonstrate that: (1) HSV-1 encompassed in Candida biofilm is protected from inactivation by physical (laser) and pharmacological (acyclovir or foscarnet) treatments; (2) the drug antiviral activity is reduced at a similar extent for both sessile or planktonic Candida.

Viscosity is an important factor of resistance to alcohol-based disinfectants by pathogens present in mucus

Alcohol-based disinfectants play an important role in the prevention of healthcare-acquired infection (HAI). We investigated whether pathogens present in mucus acquire resistance to alcohol-based disinfectants, and elucidated the underlying mechanism. Both the resistance of influenza A virus and Escherichia coli to alcohol-based disinfectants or ultraviolet irradiation and the diffusion rate of ethanol were determined in artificial mucus or sputum samples obtained from 27 individuals with acute upper respiratory infection. Pathogens in mucus (artificial mucus or sputum samples) were not completely inactivated by alcohol-based disinfectants (survival rate >10%), suggesting that the alcohol-based disinfectants were ineffective. Pathogen survival and mucus viscosity were strongly correlated (correlation coefficient >0.7, P < 0.001). Additionally, the ethanol diffusion rate decreased with increasing mucus viscosity, which contributed to ethanol resistance. Pronase treatment of sputum samples significantly decreased sputum viscosity and increased the disinfectant effect (P < 0.001 for all). In contrast, complete inactivation was achieved by ultraviolet irradiation independently of mucus viscosity. Thus, mucus viscosity contributes to resistance of pathogens to alcohol-based disinfectants by decreasing the alcohol diffusion rate. These findings can provide a basis for developing new strategies, including improved disinfectants, for overcoming HAI.