Do European Standard Disinfectant tests truly simulate in-use microbial and organic soiling conditions on food preparation surfaces?

Synergistic Strategies of Heat and Peroxyacetic Acid Disinfection Treatments for Salmonella Control

The food industry has recognized a pressing need for highly effective disinfection protocols to decrease the risk of pathogen emergence and proliferation in food products. The integration of antimicrobial treatments in food production has occurred as a potential strategy to attain food items of superior quality with respect to microbiological safety and sensory attributes. This study aims to investigate the individual and synergistic effects of heat and peroxyacetic acid on the inactivation of bacterial cells, considering various contact times and environmental conditions. Four Salmonella serotypes, isolated from industrial meat production surfaces, were employed as model organisms. By systematically assessing the impacts of individual factors and synergistic outcomes, the effectiveness of bacterial cell inactivation and the efficiency of heat and peroxyacetic acid could be predicted. To better approximate real-world food processing conditions, this study also incorporated a bovine albumin-rich condition as a simulation of the presence of organic loads in processing steps. The findings revealed the essential need for a synergistic interplay of investigated parameters with the following optimized values: 1.5% concentration of peroxyacetic acid, temperature range of 60-65 °C, and contact time of 3 min for the complete effect regardless of the degree of contamination.

Use of the European standardization framework established by CEN/TC 216 for effective disinfection strategies in human medicine, veterinary medicine, food hygiene, industry, and domestic and institutional use - a review

The SARS-CoV-2 pandemic illustrates the necessity of effective preventive measures for existing and newly emerging pathogens. When confronted with pathogens or spoilage agents, especially if they are not yet well studied, effective hygiene protocols are needed immediately. In the medical field, effective preventive measures are key to prevent vulnerable patients from infections. In production areas, effective hygiene measures are needed to protect goods from spoilage or microbial contamination. The European standardization framework established by the European Committee for Standardization (CEN) ensures that effective hygiene measures are available and can be immediately implemented when needed. Based on a broad portfolio of standards/laboratory tests, activity claims specifically addressing the special features of applications of antimicrobial formulations are substantiated. In this review, the concept of using standardized surrogate test organisms is explained, and the European standardized test approach to claim microbicidal and virucidal efficacy, the specificity of claims and their relevance for infection prevention measures is illustrated. Furthermore, relevance of the European Norm test methods is elucidated in the light of legal requirements. Finally, the review explains the systematics of the standardized methodological portfolio of CEN, Technical Committee 216, which is very useful when effective strategies for fighting or preventing microbial and viral induced infections, contaminations or spoilage are needed on an immediate basis.

Antimicrobial Activity of a Novel Cu(NO3)2-Containing Sol-Gel Surface under Different Testing Conditions

In this study, assessment of the antimicrobial activity of a novel, plasma-cured 2.5% (w/v) Cu(NO₃)₂-containing sol–gel surface was performed. In contrast to state-of-the-art sol–gel coatings, the plasma curing led to a gradient in cross-linking with the highest values at the top of the coating. As a result, the coating behaved simultaneously hard, scratch-resistant, and tough, the latter due to the more flexible bulk of the coating toward the substrate. Further, the diffusion and permeation through the coating also increased toward the substrate. In our study, tests according to ISO 22196 showed antibacterial activity of the 2.5% (w/v) Cu(NO₃)₂-containing sol–gel surface against all bacterial strains tested, and we expanded the testing further using a “dry” evaluation without an aqueous contact phase, which confirmed the antimicrobial efficacy of the 2.5% (w/v) Cu(NO₃)₂-containing sol–gel surface. However, further investigation under exposure to soiling with the addition of 0.3% albumin, used to simulate organic load, led to a significant impairment in the antibacterial effect under both tested conditions. Furthermore, re-testing of the surface after disinfection with 70% ethanol led to a total loss of antibacterial activity. Our results showed that besides the mere application of an antimicrobial agent to a surface coating, it is also necessary to consider the future use of these surfaces in the experimental phase combining industry and science. Therefore, a number of tests corresponding to the utilization of the surface should be obligative on the basis of this assessment.

Survival and inactivation of human norovirus GII.4 Sydney on commonly touched airplane cabin surfaces

Human norovirus (HuNoV) is one of the leading causes of acute gastroenteritis globally. HuNoV outbreaks have been recently reported during air travels. Contaminated surfaces are known as a critical transmission route at various settings. The aim of this study was to provide key information about the survival and the decontamination of HuNoV on three commonly touched airplane cabin surfaces. In this study, we monitored the survival of HuNoV on seat leather, plastic tray table, and seatbelt for 30 days, with and without additional organic load (simulated gastric fluid). The efficacy of two EPA registered anti-norovirus disinfectants were also evaluated. Results showed that HuNoV was detected at high titers (>4 log₁₀ genomic copy number) for up to 30 days when additional organic load was present. Both tested disinfectants were found highly ineffective against HuNoV when the surface was soiled. The study showed that when the organic load was present, HuNoV was highly stable and resistant against disinfectants. Findings from this study indicated that appropriate procedures should be developed by airline companies with the help of public health authorities to decrease passengers' exposure risk to HuNoV.

Survival and inactivation of Salmonella enterica serovar Typhimurium on food contact surfaces during log, stationary and long-term stationary phases

One of the most important transmission routes of foodborne pathogens is through contaminated food contact surfaces. In this study, we investigated the survival and inactivation of Salmonella enterica serovar Typhimurium on frequently used food contact surfaces in household settings, including plastic cutting board (CB), formica laminate (LA), and stainless steel (SS) surfaces. S. Typhimurium at log (6 h), stationary (24 h), or long-term stationary (LTS) (14 days) phases were evaluated. Results showed that, at medium and high microbial loads, LTS phase cells had significantly higher survivor population compared to log and stationary phase cells at 24 h after inoculation (p < 0.05). Disinfection study showed that LTS phase cells were very resilient to sodium hypochlorite when the initial microbial load was high with disinfection efficacy ranging from 26 to 35%. Scanning electron microscopy of these surfaces at 24 h after inoculation with a high microbial load revealed an early biofilm structure.

Antimicrobial susceptibility and sessile behaviour of bacteria isolated from a minimally processed vegetables plant

In this study, 20 heterotrophic bacteria from a minimally processed vegetables (MPV) plant were tested for their susceptibilities to five antibiotics (tetracycline, erythromycin, ampicillin, levofloxacin and ciprofloxacin), their (co)aggregation abilities and their survival under gastric simulated conditions. Peracetic acid (PA) and sodium hypochlorite (SH), both at 50 ppm, were evaluated for their abilities to control biofilms of these bacteria. In general, the Gram-negative bacteria were found to be more resistant to the selected antibiotics. Two isolates, Rhanella aquatilis and Stenotrophomonas maltophilia, demonstrated multidrug resistance. Only Rhodococcus erythropolis presented aggregation potential, while no bacterium survived under the gastric conditions. The biofilm experiments showed PA as less efficient than SH in killing biofilms and neither of the disinfectants was able to fully eliminate the biofilms. Significant regrowth was observed for most of the biofilms. The results indicate that alternative and/or complementary disinfection strategies are required to guarantee food safety.

In vitro methods for the evaluation of antimicrobial surface designs

Bacterial adhesion and subsequent biofilm formation on biomedical implants and devices are a major cause of their failure. As systemic antibiotic treatment is often ineffective, there is an urgent need for antimicrobial biomaterials and coatings. The term "antimicrobial" can encompass different mechanisms of action (here termed "antimicrobial surface designs"), such as antimicrobial-releasing, contact-killing or non-adhesivity. Biomaterials equipped with antimicrobial surface designs based on different mechanisms of action require different in vitro evaluation methods. Available industrial standard evaluation tests do not address the specific mechanisms of different antimicrobial surface designs and have therefore been modified over the past years, adding to the myriad of methods available in the literature to evaluate antimicrobial surface designs. The aim of this review is to categorize fourteen presently available methods including industrial standard tests for the in vitro evaluation of antimicrobial surface designs according to their suitability with respect to their antimicrobial mechanism of action. There is no single method or industrial test that allows to distinguish antimicrobial designs according to all three mechanisms identified here. However, critical consideration of each method clearly relates the different methods to a specific mechanism of antimicrobial action. It is anticipated that use of the provided table with the fourteen methods will avoid the use of wrong methods for evaluating new antimicrobial designs and therewith facilitate translation of novel antimicrobial biomaterials and coatings to clinical use. The need for more and better updated industrial standard tests is emphasized.

STATEMENT OF SIGNIFICANCE

European COST-action TD1305, IPROMEDAI aims to provide better understanding of mechanisms of antimicrobial surface designs of biomaterial implants and devices. Current industrial evaluation standard tests do not sufficiently account for different, advanced antimicrobial surface designs, yet are urgently needed to obtain convincing in vitro data for approval of animal experiments and clinical trials. This review aims to provide an innovative and clear guide to choose appropriate evaluation methods for three distinctly different mechanisms of antimicrobial design: (1) antimicrobial-releasing, (2) contact-killing and (3) non-adhesivity. Use of antimicrobial evaluation methods and definition of industrial standard tests, tailored toward the antimicrobial mechanism of the design, as identified here, fulfill a missing link in the translation of novel antimicrobial surface designs to clinical use.

Use of 70% alcohol for the routine removal of microbial hard surface bioburden in life science cleanrooms

ABSTRACT 

Alcohol-based disinfectants are used for the removal of microbial hard surface bioburden in Life science Cleanrooms. Evidence for using formulations containing 70% alcohol has been lost over time but probably originates from historical observations of the activity of 60–70% alcohol. Tradition is no longer adequate to inform contemporary cleaning practice. We evaluated the efficacy of ethanol, isopropanol and trade-specific denatured alcohol 7 against vegetative Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Enterococcus hirae using standardized European Suspension and Hard Surface tests. All three alcohols were effective at lower concentrations than the 70% standard. This constitutes the first evaluation of disinfectant formulations containing ≤70% alcohol using standard methodology. The utility of trade-specific denatured alcohol #7 and evidence-based cleanroom practice warrant further validation.

Comparative efficacy evaluation of disinfectants routinely used in hospital practice: India

AIM

The aim of this study was to evaluate and compare practically achieved disinfection efficacy of some locally available disinfectants on surfaces and infectious microbiological hospital waste.

MATERIALS AND METHODS

Seven disinfectants were tested at concentrations recommended by manufacturers on rough and smooth surfaces that were contaminated experimentally by locally circulating isolates of methicillin-resistant Staphylococcus aureus, multidrug-resistant Acinetobacter baumannii, Klebsiella pneumoniae, Enterobacter aerogenes, Pseudomonas aeruginosa strains, standard isolate of Salmonella typhi and Candida albicans. Reduction in microbial counts before and after surface disinfection was expressed as log reduction. A very heavy microbial waste load was simulated by immersing culture plates with heavy microbial growth in disinfectants. Daily, a sample of disinfectant was taken and subjected to in-use test.

RESULTS

The highest average log reduction of test microbes on the rough surface was given by DesNet (5.05) and Bacillocid special (5.02). A comparable average log reduction of test microbes on a smooth steel surface was noted (5.68, 5.67, 5.50) for Lysol, Bacillocid sp. and DesNet, respectively. In the discard jars, Bacillocid special worked satisfactorily for 4 days, DesNet for 3 days and Hi-giene Germitol for 1 day. The remainder of the disinfectants failed in the in-use test on Day 1. Phenolics, although widely used in our settings, may not be as good surface disinfectants as newer formulations like DesNet and Bacillocid special.

CONCLUSIONS

Newer quaternary ammonium compounds and aldehyde formulations were found to be the best disinfectants for disinfection of heavy contamination.

New insights for rapid evaluation of bactericidal activity: a semi-automated bioluminescent ATP assay

AIMS

  A new assay, much more rapid and efficient than the existing standardized tests, is introduced for the evaluation of bactericidal activity of chemical disinfectants and antiseptics under simulated practical conditions of use.

METHODS AND RESULTS

  The bactericidal activity of biocides was quantified using a novel semi-automated assay based on the European Norm (EN) standard suspension tests but determining bacterial cell viability by intracellular adenosine tri-phosphate (ATP) content quantification instead of traditional culture-based microbiological techniques. The new test was validated by comparison to the standard suspension tests EN 1276 and EN 13727. During the validation, the linearity of the ATP detection system, limit of detection, specificity, sensitivity, relative accuracy and precision (repeatability and reproducibility) were determined.

CONCLUSIONS

  The validation study showed that the new assay evaluates the activity of biocides as well as the EN standard suspension tests, but it allows a large number of test conditions to be efficiently analysed.

SIGNIFICANCE AND IMPACT OF THE STUDY

  The new test can therefore be applied to accurately establish the lowest active concentration (MBCs) of disinfectants or antiseptics under simulated practical conditions of use and to compare the susceptibility of a large number of strains and conditions via inactivation curves. This is not possible in any reasonably practicable way with the EN standards considering the time and cost required for each determination.

Evaluation of the sporicidal activity of different chemical disinfectants used in hospitals against Clostridium difficile

Decontamination of surfaces and medical equipment is integral to the control of Clostridium difficile transmission, and many products claim to inactivate this bacterium effectively. Thirty-two disinfectants were tested against spores of C. difficile in a suspension test based on European Standard BS EN 13704:2002, with contact times of 1 and 60 min in simulations of clean (0.3% albumin) and dirty (3% albumin) conditions. The addition of a 1-min contact time was chosen as a more realistic simulation of probable real-life exposures in the situation being modelled than the 60 min specified by the Standard. The manufacturer's lowest recommended concentrations for use were tested. Sixteen products achieved >10(3) reduction in viability after 60 min (the pass criterion for the Standard) under both clean and dirty conditions. However, only eight products achieved >10(3) reduction in viability within 1 min under dirty conditions. Three products failed to reduce the viability of the C. difficile spores by a factor of 10(3) in any of the test conditions. This study highlights that the application of disinfectants claiming to be sporicidal is not, in itself, a panacea in the environmental control of C. difficile, but that carefully chosen environmental disinfectants could form part of a wider raft of control measures that include a range of selected cleaning strategies.