https://www.trueceylonspices.com/wp-content/uploads/Bactericidal-activities-of-plant-essential-oils.pdf

Bactericidal activities of plant essential oils and some of their isolated constituents against Campylobacter jejuni, Escherichia coli, Listeria monocytogenes, and Salmonella enterica.

Mode-of-action studies concluded that alkyldimethylbenzylammonium chloride (ADBAC) (a blend of C12, C14 and C16 alkyl homologues) and didecyldimethylammonium chloride (DDAC) are both membrane-active agents, possessing subtly different modes of action reflecting early cell interactions against Staphylococcus aureus. ADBAC and DDAC exhibited similar MIC behaviors from 0.4 ppm to 1.8 ppm over an inoculum range of 1 × 105 to 1 × 109 CFU/ml at 35°C. For ADBAC and DDAC, an increased rapidity of killing against S. aureus (final concentration, 2 × 109 CFU/ml) was observed at 35°C compared to 25°C. Concentration exponents (η) for killing were <2.5 for both agents, and temperature influenced the η value. Examination of leakage and kill data suggested that a single leakage marker was not indicative of cell death. ADBAC and DDAC possessed Langmuir (L4) and high-affinity (H3/4) uptake isotherms, respectively. ADBAC molecules formed a single monolayer of coverage of cells at the end of primary uptake, and DDAC formed a double monolayer. Rapid cell leakage occurred at bactericidal concentrations, with total depletion of the intracellular potassium and 260-nm-absorbing pools released in this strict order. Autolysis was observed for ADBAC and DDAC at concentrations of 9 μg/ml (0.0278 mM and 0.0276 mM, respectively) and above, together with the depletion of approximately 30% of the internal potassium pool. Autolysis contributed to ADBAC and DDAC lethality, although high biocide concentrations may have inhibited autolytic enzyme activity.

Action of Disinfectant Quaternary Ammonium Compounds against Staphylococcus aureus

Part 1 Risks: Range of microbial risks in food processing Biofilm risks Pathogen resistance to sanitisers Aerosols as a contamination risk Consumer perceptions of risks from food. Part 2 Improving design: Improving building design Improving zoning within food processing plants Improving the design of floors Improving design of walls Improving the hygienic design of closed equipment, heating equipment, equipment handling dry materials, packaging equipment, electrical equipment, valves, pipes, pumps, sensors. Part 3 Improving hygiene management and methods: Risk assessment in hygiene management Good Manufacturing Practice (GMP) in the food industry The use of Standard Operating Procedures (SOPs) Managing risks from allergenic residues Managing contamination risks from food packaging materials Improving hygiene in food transportation Improving control of insects in food processing Improving cleaning in place (CIP) Improving cleaning out of place (COP) Improving cleaning of heat exchangers Improving cleaning of tanks Ozone decontamination in hygiene management Enzymatic cleaning in food processing Contamination routes and analysis in food processing environments Testing surface cleanability in food processing Improving the monitoring of fouling, cleaning and disinfection in closed process plant Improving surface sampling and detection of contamination Improving air sampling Testing effectiveness of disinfectants and sanitisers Traceability of disinfectants and sanitisers Improving hygiene auditing.

Handbook of Hygiene Control in the Food Industry

This paper reports the preparation of poly(sodium acrylate) (PSA) cryogels decorated with silver nanoparticles (AgNPs) for point-of-use (POU) water disinfection. The PSA/Ag cryogels combine the high porosity, excellent mechanical and water absorption properties of cryogels, and uniform dispersion of fine AgNPs on the cryogel pore surface for rapid disinfection with minimal Ag release (<100 μg L–1). They were used in a process that employed their ability to absorb water, which subsequently could be released via application of mild pressure. Their antibacterial performance was evaluated based on the disinfection efficacies of E. coli and B. subtilis. The PSA/Ag cryogels had excellent disinfection efficacies showing close to a 3 log reduction of viable bacteria after a brief 15 s contact time. They were highly reusable as there was no significant difference in the disinfection efficacies over five cycles of operation. The biocidal action of the PSA/Ag cryogels is believed to be dominated by surface-controlle...

Superabsorbent Cryogels Decorated with Silver Nanoparticles as a Novel Water Technology for Point-of-Use Disinfection

Aims: The method of the sum of the fractional inhibitory concentrations (∑FIC) is used ubiquitously in the investigation of antimicrobial combinations. The inherent assumption of this simple equation is that in a mixture all antimicrobials have identical dose responses. The aim of this work was to analyse the outcome of removing this assumption.



Methods and Results: A model to describe the efficacy of combined inhibitors was produced which removed the assumption of identical dose responses. The results of several checkerboard experiments showed that the new model, termed the facomb was a more general form of the ∑FIC method, but the features described by the ∑FIC as either synergy or antagonism could be attributed to differences in the dose responses of antimicrobials in combination. Where the model failed to adequately describe experimental data it was suggested that these might be cases of true antagonism or synergy.



Conclusions: The ∑FIC methodology used to describe the effect of antimicrobial combinations (preservatives and antibiotics) is valid only when it is demonstrated that individual components of the mixture have identical dose responses. Otherwise the ∑FIC method is invalid. Descriptions of antimicrobial synergy may simply be due to the mixing of antimicrobials with differing dose responses.



Significance and Impact of the Study: Studies aimed at producing synergistic mixtures of antimicrobials, which ignore the dose response of the individual antimicrobials, may waste valuable research effort looking for a physiological explanation for an apparent synergy, where none, in-fact, exists. Conversely, mixing antimicrobials with very different dose responses might lead to mixtures with an ‘apparent’ synergy which may themselves be very useful therapeutically.

https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2672.2003.02039.x

A model for the efficacy of combined inhibitors.

A new method is described for screening potential biocides based on the traditional suspension test using the Bioscreen optical plate reader. This new method is rapid, reproducible, quantitative and cost effective. Data obtained by this new method are not directly equivalent to the log reduction normally quoted, but give a measurement of the total effect of the biocide on the microbe population, measuring the effect of injury as well as death (non-viability). The method allows for the routine examination of disinfection kinetics, the study of which leads to greater scientific insight into disinfection than that achieved by the standard 5 min, one-point, disinfection tests currently employed.

Johnston

Papers

Disinfectant testing: use of the Bioscreen Microbiological Growth Analyser for laboratory biocide screening