A Pilot Study on Novel Elastomers’ Antimicrobial Activity Against Legionella pneumophila and Salmonella Enteritidis
by
, , , , , , and
Marina Tesauro
1,2
,
Valerio M. Sora
1,*,
Gabriele Meroni
1,
Michela Consonni
1,
Francesca Zaghen
1,3,
Giulia Laterza
1,3,
Piera Anna Martino
1 and
Alfonso Zecconi
1 1
Department of Biomedical, Surgical and Dental Sciences-One Health Unit, School of Medicine, University of Milan, Via Pascal 36, 20133 Milan, Italy
2
Coordinated Research Center “EpiSoMI”, University of Milan, Via Carlo Pascal 36, 20133 Milan, Italy
3
Department of Clinical and Community Sciences, School of Medicine, University of Milan, Via Celoria 22, 20133 Milan, Italy
*
Author to whom correspondence should be addressed.
Appl. Sci. 2025, 15(10), 5632; https://doi.org/10.3390/app15105632
Submission received: 25 March 2025
/
Revised: 9 May 2025
/
Accepted: 15 May 2025
/
Published: 18 May 2025
Abstract
:Featured Application
By establishing these elastomers as potential materials to improve microbiological safety in critical situations and in new technical applications, their use in settings such as drinking water systems, hospitals, and dental offices—where infectious microorganisms pose a serious health threat to humans—could help safeguard public health.
Abstract
Both synthetic and natural rubber-like elastomers are widely employed in industrial applications (such as tires, seals, protective gloves, and damping absorbers) as well as in the food and animal husbandry industries. These materials should be regularly checked for contamination and the associated infectious risk since they frequently come into contact with food, animals, and people. Additionally, they could act as vehicle of microbes and, as a result, diseases. This pilot study investigates the antibacterial efficacy of novel elastomer formulations against Salmonella enterica subsp. enterica serovar Enteritidis and Legionella pneumophila, with possible applications in drinking water distribution systems (DWDSs). This study aims to evaluate the antimicrobial activity of two rubber and five silicone patented elastomers with antibacterial additives. Two microbiological concentrations (103 and 104 CFU/mL) were used to compare the efficacy of the elastomers. The results showed a significant decrease in bacterial load in several silicone formulations, with two of them showing the strongest bactericidal efficacy against L. pneumophila (0% and 3% survival rates for VMQ105 and VMQ500L formulations, respectively), despite the wide variations in S. Enteritidis inhibition. One rubber elastomer performed better than the other in terms of reducing bacterial survival for both pathogens (NBRCA) while NBROM showed a 0% survival rate only for L. pneumophila. The findings suggest that certain elastomer compositions might lessen the potential infectious risks in water systems or contaminated matrices. Future research may investigate in situ applications, particularly in hospitals or dental offices where these pathogens pose major health risks.
1. Introduction
Food contact materials (FCMs) include all materials (rubber, plastic, metal, ceramics, paper, and ink) that come into contact with food and drinks, such as containers and packaging, and also those used in food processing equipment or transport. Chemicals in FCMs, such as styrene, phthalates, and bisphenol A, could be transferred into the food, water, and drinks we consume. The European Food Safety Authority (EFSA) evaluates whether there are possible health risks due to such a transfer based on migration and toxicological data and periodically publishes technical reports and scientific opinions on this issue (https://www.efsa.europa.eu/en/topics/topic/food-contact-materials, accessed on 16 April 2025).
In addition, there is a microbiological hazard, since microorganisms in food or water can adhere to the biofilm that forms on FCMs, multiply, and be released in great numbers [1,2]. In recent decades, an increasing level of antimicrobial resistance in microorganisms has been observed, mainly due to the prolonged use of antimicrobial drugs, leading to a crucial problem in public health. Therefore, FCMs could act as vehicles of pathogens, causing antimicrobial resistance and infection [3,4]. For these reasons, new solutions are necessary and there is continuous research for novel materials that meet the characteristics of healthfulness and ease of production and use, according to international regulations (Regulation (EC) No 1935/2004, 2023/2006, and 1381/2019).
The term “elastomer” combines the words “elastic” and “polymer”. Elastomers are polymeric materials characterized by both elastic and viscous properties that can undergo significant elastic deformations with no fracture. Elastomers can be of synthetic or natural origin, as rubbers are extensively employed not only in industrial uses (e.g., tires, seals, protective gloves, and damping absorbers) [5], but also in food industries and food-producing animal activities [6].
A common application of elastomers is in the drinking water distribution system (DWDS). In this system, materials in contact with water must not alter the natural characteristics of water (smell, taste, and color) and its wholesomeness over time. Furthermore, these materials must not promote microbial growth (i.e., biofilm), avoiding compromising human health directly or indirectly. Additive polymers are used in medicine to create antimicrobial active medical devices to prevent hospital-acquired infections [7]. Previous research of our group [6] evaluated the antimicrobial activity of two different types of nationally patented and internationally patent-pending elastomers (rubber and silicone) and nine formulations against three major dairy cow mastitis pathogens (Staphylococcus aureus, Streptococcus agalactiae, and Escherichia coli), simulating the application of these elastomers in teat liners applied to cow milking machines. Based on the proven antimicrobial action of silver-based molecules and zinc pyrithione [8,9,10], the positive results of previous work and research published in the literature, such as from Pittol and colleagues [11], supported the present study which investigates novel (commercially available from 1 January 2025) elastomers to be used against Salmonella enterica subsp. enterica serovar Enteritidis and Legionella pneumophila in the food industry and DWDSs. Indeed, Salmonella enterica subsp. enterica serovar Enteritidis and Legionella pneumophila are common microorganisms that are involved in foodborne and waterborne infections and play a crucial role in the hygienic–sanitary quality of food production and water distribution [12,13,14,15,16]. The occurrence of food and water-borne infections highlights the need to increase the availability of materials and knowledge for their possible applications in processing activities and transport, without the necessity of adding ex novo/increasing the quantity of antimicrobial products used as disinfectants in the aforementioned activities, but, on the contrary, minimizing the use of further chemical products and exploiting the antimicrobial properties of the elastomers examined. Therefore, this study aims to evaluate the in vitro antimicrobial activity of different formulations of elastomers against these two bacteria for new in situ applications in food industries and/or DWDSs.
2. Materials and Methods
2.1. Elastomer Characteristics
Six distinct silicone (including controls) and two rubber elastomers (with respective controls) formulations, based on performances assessed in a previous study [6], were evaluated in this study. Patented antimicrobial additives (PAAs) were included in each of them. Both of the elastomers and all of the additives are approved by the United States Food and Drug Administration (USFDA) for their use and contact with food. Table 1 and Table 2 provide a thorough breakdown of the main components.
2.2. Bacterial Species and Culture Conditions Used
Legionella pneumophila ATCC 33152 and Salmonella enterica subsp. enterica serovar Enteritidis ATCC 25928 (later referred to as S. enteritidis) were used to evaluate the antimicrobial activity for DWDSs and food contamination settings, respectively. Starting from a −20 °C bacterial stock, 10 µL of S. enteritidis were plated on Tryptic Soy Agar (Microbiol, Macchiareddu, Italy) and aerobically incubated overnight at 37 °C. L. pneumophila ATCC 33152 was cultivated on Buffered Charcoal Yeast Extract Agar (BCYE—Oxoid Ltd., United Kingdom) for ten days at 37 °C and 2.5% CO2. Bacteria inocula were prepared by resuspending bacterial colonies into a sterile saline solution (NaCl, 0.9% w/v) until reaching a concentration of 0.5 McFarland units (equal to 1.5 × 108 colony forming units/mL (CFU/mL)) determined with a densitometer (BioSan, Medical-Biological Research and Technologies, Riga, Latvia). From each bacterial inoculum, serial dilutions in a sterile saline solution were performed to obtain 104 and 103 CFU/mL final concentrations.
2.3. Sample Preparation and Antibacterial Activity Test
The methods have been previously described by Meroni et al. [6]. Briefly, each elastomer sheet was cut into a circular shape of 1.21 cm2 and placed at the bottom of a 24-well plate (Cellstar, Greiner bio-one, Milan, Italy); subsequently, 1 mL of each bacterial suspension was pipetted into each well. A sterility control, consisting of a well of a plate filled with an elastomer disc and 1 mL of the same stock of saline solution previously used to prepare the bacterial suspension for each 24-well plate, was added. The elastomer antibacterial activity was evaluated at four distinct time points: T0 (contact), T1 (one hour after contact), T2 (six hours after contact), and T3 (twenty-four hours after contact). Fifty µL of the bacterial suspension of S. enteritidis were taken from each well at each time point, plated on Tryptic Soy Agar (Micro-biol, Italy), and then incubated aerobically for 24 h at 37 °C. The same was performed for L. pneumophila except for the medium used (BCYE) and the incubation parameters (ten days at 37° and 2.5% CO2).
For both microorganisms and all elastomers, the antimicrobial activity was tested in triplicate at each time point. After incubation, the colonies were counted on each plate.
2.4. Statistical Analysis
Data were collected in an Excel spreadsheet, and the survival rate was calculated using the following equation:
where S (%) is the surviving bacterial population (percentage, %), CFUtn is the bacterial concentration (CFU/mL) at time n > 0, and CFUt0 is the initial bacterial concentration (CFU/mL). The killing activity during the full 24 h follow-up period was compared using the Kaplan–Meier technique (XLstat 2023.1.4 Addinsoft, New York, NY, USA). Even when time is erratic, the Kaplan–Meier approach enables the comparison of populations using their survival curves.
3. Results
The results of the antimicrobial activity against Legionella pneumophila and Salmonella enteritidis observed for silicone elastomers are reported in Table 3, while Table 4 corresponds to the rubber ones.
3.1. Silicone Elastomers
When looking at the silicone-based elastomers, it was noted that all of the tests showed a decrease in microbial counts for both microorganisms, including the controls. However, the difference in percentage of the median survival rate between the controls and silicone was statistically significant for silicones VQM500L, VQM561D, and VQM561L against both Legionella and Salmonella, except VQM500D, where the difference was statistically significant for Legionella but not for Salmonella, and VQM105 where a significantly lower activity was observed for Salmonella at 103 CFU/mL.
Looking at Table 3, it is evident that VQM105 was more effective in reducing L. pneumophila growth than other formulations, immediately followed by VQM500L and VQM500D. In the case of S. enteritidis, formulation VQM105 is curiously effective only at the concentration of 104 CFU/mL, while the best action against survival rate (%) is represented by VQM500L.
3.2. Rubber Elastomers
Table 4 compares the median survival rates, expressed as percentage, in rubber elastomers vs. controls. It is noted that, in the case of NBROM, the difference is statistically significant between rubber and the controls both in L. pneumophila and S. enteritidis, while in the other rubber named NBRCA, a difference is observed only for L. pneumophila and S. enteritidis at 104 CFU/mL.
In the comparison of the two rubber elastomers (NBROM and NBRACA), the most effective one for killing L. pneumophila was the NBROM formulation at both concentrations; however, NBRCA also showed significant effectiveness, achieving a survival rate of less than 5% for L. pneumophila and less than 10% for S. enteritidis.
Otherwise, we did not observe a clear efficacy in reducing Salmonella in a specific formulation of rubber, noticing a worse action at 103 CFU/mL rather than 104 CFU/mL in both NBRCA and NBROM.
Interestingly enough rubber control CACONT presented good activity against S. enteritidis, but the same was not observed against L. pneumophila, while OMCONT showed to be active vs. L. pneumophila like its additive counterpart and to be more active than NBROM against S. enteritidis.
4. Discussion
Elastomers are manufactured or natural polymeric materials with elastic and viscous qualities that are widely used in the food and medical industries, in addition to industrial settings. Investigations on the antimicrobial activity of newly formulated compounds on microorganisms responsible for nosocomial or foodborne infections are relatively few.
The present study aimed to evaluate the antimicrobial activity of 10 different elastomers (two treated rubbers and two controls, five treated silicones and one untreated control) against L. pneumophila and S. enteritidis, which are considered indicators to be of water quality in specific environmental/artificial conditions and fecal pollution in DWDSs or in food industries.
The tested elastomers, in addition to the control composition, contain additives (already approved by the USFDA) with antimicrobial properties. They were tested at two different bacterial concentrations and compared to elastomers without additives used as controls. The elastomers with additives are patented and the specific composition was known only at the end of the experiments; their composition is reported in Table 1 and Table 2. According to the manufacturer’s information, the antimicrobial action is due to the contact of the microorganisms to the elastomer surface and not to the spread of the additives in the tested solution, as confirmed by the UNI EN 13130-1:2005 [17] test procedure for specific migration, with values of <0.0001 mg/kg.
It is worth noting that L. pneumophila growth was better controlled by silicone VQM105, followed by VQM500L at both concentrations. The survival rate of S. enteritidis was less clearly defined, sometimes showing better results at 104 CFU/mL and other times at 103 CFU/mL. Rubber elastomers revealed better antimicrobial efficacy of NBROM than NBRCA on L. pneumophila and reverse results on S. enteritidis. These unexpected results could depend on the low counts of the tested solution and/or on the mechanisms or method of exposure to the antimicrobial additives.
L. pneumophila seemed to be more susceptible for reasons that cannot be conclusively demonstrated. There is not a specific literature on this topic or even experience on these elastomers reported from other research groups; the data presented herein are the first set of experiments on these materials and on these microorganisms. It could be speculated that the differences may depend on the different interactions with the substrate, on the greater adhesion properties or on the different communication capabilities through the quorum sensing of L. pneumophila compared to S. enteritidis. More experiments need to be carried out on these specific topics to confirm or deny these hypotheses.
VQM105 is a complete silicone formulation containing both accelerators, zinc oxide and magnesium oxide, which are known to be additives that improve abrasion resistance and are crosslinkers for viscosity enhancement at the manufacturing stages. For these compounds, a small amount of antibacterial action is already recognized, as demonstrated by a recent study [18]. In the VQM105 formulation, all antimicrobial silver-based additives and zinc pyrithione, whose antibacterial and antifungal action is already demonstrated, were present. The other silicone formulations are still efficacious against L. pneumophila and S. enteritidis, although in different and sometimes contrasting ways. These different levels of antimicrobial activity could depend on the absence of one of the main components and/or one of the accelerators that could change the structure of the elastomers and therefore the exposure of the tested bacteria to the antimicrobial additives.
Overlapping activity was observed in the case of the complete formulation NBROM, including the already mentioned accelerators and antimicrobial additives. It showed complete efficacy versus L. pneumophila but much less toward S. enteritidis (a 0% vs. 18.5% survival rate). NBRCA seems to be more active against both bacteria, assuming that it could depend on the different composition and structure of this latter rubber which contains different compounds and accelerators.
In a recent literature search regarding elastomers and their antimicrobial activity, it was found that there are two main areas of research, one more common on in vitro experiments and the other on the application of new molecules or active compounds in different fields. For instance, Iyigundogdu and colleagues investigated thermoplastic elastomers (TPEs) incorporated with six different formulations for mechanical and antiviral performance, showing that TPE samples containing zinc pyrithione and disodium octaborate tetrahydrate presented biocidal action against several pathogens (Staphylococcus aureus, Methicillin Resistant S. aureus, Escherichia coli, Candida albicans, Aspergillus niger, Adenovirus, Bovine Coronavirus, Poliovirus, and Norovirus), and these formulations can be used to develop antimicrobial products for multiple touchpoints within a vehicle and micro-mobility [8]. Some authors have demonstrated that silver is an antibacterial agent with high activity and limited bacterial resistance. The mechanism of action relies on positively charged silver ions (Ag+) attracting the sulfhydryl group on the enzyme protein in the bacteria. Particularly, in a Graphene oxide–Ag nanocomposite, bactericide action against the Gram-negative E. coli occurred through disrupting bacterial cell wall integrity, whereas a bacteriostatic effect inhibiting cell division for Gram-positive S. aureus was demonstrated [19,20]. The compound silver and tannin modified hydroxyapatite may serve as a promising and easy-to-produce antimicrobial mineral for the development of antimicrobial orthopedic composite implants to prevent surgical infections [21], while for other clinical applications of elastomers, leakage resistance and the antimicrobial properties of porous liquid metal–elastomer composites for skin-interfaced bioelectronics were verified [22].
Quintero-Quiroz and colleagues incorporated Ag nanoparticles (AgNPs) into a silicone elastomer to assess their antimicrobial activity, along with their physico-mechanical properties and cytotoxic effects, for developing prosthetic liners, and measured the maximum antimicrobial activity vs. S. aureus and methicillin-resistant S. aureus [23].
Sehmi et al. demonstrated that polyurethane containing crystal violet and zinc oxide nanoparticles have excellent bactericidal activity against hospital-acquired pathogens, including multidrug-resistant E. coli, Pseudomonas aeruginosa, methicillin-resistant S. aureus, and endospores of Clostridioides difficile, hoping to implement their use to reduce the transmission of pathogens between people and the environment [24].
Antimicrobial activity was also tested in the textile industry in instances of medical and personal protection applications by examining four types of antimicrobial fillers, namely, metal oxides (zinc, titanium, and copper) and nanosilver, as fillers in Polyamide 12 fibers. In these studies, it was found that metal oxides combined with silver showed significantly higher antifungal activity than those with only a mixture of metal oxides [25].
Finally, Meroni et al. [6] tested innovative elastomers, different from those considered in this paper, against the three major mastitis pathogens (S. aureus, S. agalactiae, and E. coli), for their potential use during milking and in the food industry. They noticed that basic rubber materials have intrinsic antimicrobial activity, and, on the contrary, silicone elastomers did not exhibit the same action. Nevertheless, a significant decrease in bacterial survival curves was observed for all the formulations with additives, with different results in different formulations and manufacturing processes [6]. In our study, rubber controls CACONT and OMCONT presented good activity against both bacteria in different ways, confirming an intrinsic antimicrobial activity of these elastomers.
To date, this is the first research that evaluates the antimicrobial activity of these novel and patented elastomers with additives on L. pneumophila and S. enteritidis. This could represent an advantage, as there is an increasing need to improve the knowledge on materials that could control Legionella colonization or fecal contamination in artificial pipelines, as in DWDSs or the food industry. Nevertheless, the lack of other studies on the antimicrobial activity of these elastomers, impairing the ability of the authors to compare results, could be considered a limitation. It should be added that these new elastomers exhibit very good resistance and elasticity. The spread of these materials into new market areas is also supported by the relative ease of production and cost, making future applications highly plausible. As a result of the present in vitro experiments, there is an increasing need to test the silicones’ and rubbers’ antimicrobial activity directly in situ.
Salmonella is still a major cause of foodborne illness, and its control in food processing is still suboptimal. Although the antibacterial activity of the tested elastomers against this bacterium was lower than L. pneumophila, their application in food production plants could help in lowering the overall microbial load and consequent risk of food contamination.
The good antimicrobial activity showed by some of the tested elastomers against L. pneumophila supports their application in specific water systems, such as the water systems of hospitals, where fragile patients are particularly exposed to the risk of legionellosis, or in dental clinics, where dental water lines have been shown to be colonized by L. pneumophila and where aerosols could be vehicles for microorganisms in the respiratory system of patients. [26,27,28,29,30,31,32].
5. Conclusions
The present study offers important new information on the antibacterial properties of novel elastomer formulations, especially against S. enteritidis and L. pneumophila, two important markers of water contamination and quality; nevertheless the low number of tests performed and the lack of follow-up tests on adhesion and quorum sensing of bacterial cells could be seen as a limitation of this study. Certain silicone (VMQ105 and VMQ500L) and rubber (NBROM) elastomers showed notable antibacterial activity among the tested formulations; VMQ105 was especially effective against L. pneumophila. These results lend credence to the possible use of these elastomers in settings such as drinking water systems, hospitals, and dentistry offices. Given L. pneumophila’s great vulnerability to certain formulations, further practical studies are necessary in order to better understand interactions with the tested materials and to confirm the hypothesis that adhesion properties and quorum sensing has a role in bacterial cell survivability. In the end, this might assist in safeguarding public health by establishing these elastomers as potential materials to improve microbiological safety in crucial situations, as stated above, and in new technical applications.
6. Patents
National patent: N. 102022000002048 “Composizione adatta alla realizzazione di un elastomero termoindurente con capacità antimicrobiche tramite vulcanizzazione per stampaggio”. Date of release: 2 April 2022
National patent classification: C08L
International patent application: PCT/IB2023/050905 “A composition suitable for the production of a thermosetting elastomer with antimicrobial capabilities by means of vulcanization by molding”.
International patent classification: C08K3/04 C08K3/32 C08K5/00 C08L7/00 C08L23/16 C08L27/16 C08L43/04.
Author Contributions
Conceptualization, G.M. and A.Z.; methodology, G.M., V.M.S., G.L. and M.C.; software, A.Z. and F.Z.; formal analysis, A.Z., F.Z. and V.M.S.; investigation, M.T. and A.Z.; resources, A.Z. and M.T.; data curation, V.M.S. and A.Z.; writing—original draft preparation, M.T., V.M.S. and A.Z.; writing—review and editing, P.A.M., G.L. and M.C.; supervision, M.T., V.M.S., A.Z. and P.A.M. All authors have read and agreed to the published version of the manuscript.
Funding
This study was partially funded by Scudo Technologies PRP, Italy.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Raw data are available on request from the corresponding author.
Acknowledgments
This research is part of the project “One Health Action Hub: University Task Force or the Resilience of territorial ecosystems” supported by Università degli Studi di Milano—PSR2021-GSA-Linea 6.
Conflicts of Interest
The authors declare no conflicts of interest. The funders had no role in the design of this study, the collection, analyses, or interpretation of data, the writing of the manuscript, or the decision to publish the results.
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Table 1.
The chemical composition of the six silicones tested.
| Main Components | Acronym (In Tables) |
|---|---|
| Silicon rubber (CAS 63394-02-5) 95–99% Dicumyl peroxide (CAS 80-43-3) 0.3–1.2% 2.5-Dimethyl-2,5-di(tert-butylperox) hexane (CAS 78-63-7) 0.3–1.2% | CONTROL |
| Silicon rubber (CAS 63394-02-5) 95–99% Dicumyl peroxide (CAS 80-43-3) 0.3–1.2% 2.5-Dimethyl-2,5-di(tert-butylperox) hexane (CAS 78-63-7) 0.3–1.2% Effectiveness accelerators: Zinc oxide (CAS 1314-13-2) 1–5% Magnesium oxide (CAS 1309-48-4) 1–5% Antimicrobial additive 1%: Silver chloride (CAS 7783-90-6) Silver phosphate glass (CAS 308069-39-8) Zinc pyrithione (CAS 13463-41-7) | VQM105 |
| Silicon rubber (CAS 63394-02-5) 95–99% Dicumyl peroxide (CAS 80-43-3) 0.3–1.2% Antimicrobial additive 1%: Silver chloride (CAS 7783-90-6) Silver phosphate glass (CAS 308069-39-8) Zinc pyrithione (CAS 13463-41-7) | VQM500D |
| Silicon rubber (CAS 63394-02-5) 95–99% 2.5-Dimethyl-2,5-di(tert-butylperox) hexane (CAS 78-63-7) 0.3–1.2% Antimicrobial additive 1%: Silver chloride (CAS 7783-90-6) Silver phosphate glass (CAS 308069-39-8) Zinc pyrithione (CAS 13463-41-7) | VQM500L |
| Silicon rubber (CAS 63394-02-5) 95–99% Dicumyl peroxide (CAS 80-43-3) 0.3–1.2% Effectiveness accelerators: Zinc oxide (CAS 1314-13-2) 1–5% Magnesium oxide (CAS 1309-48-4) 1–5% Antimicrobial additive 1%: Silver chloride (CAS 7783-90-6) Silver phosphate glass (CAS 308069-39-8) Zinc pyrithione (CAS 13463-41-7) | VQM561D |
| Silicon rubber (CAS: 63394-02-5) 95–99% 2.5-Dimethyl-2,5-di(tert-butylperox) hexane (CAS 78-63-7) 0.3–1.2% Effectiveness accelerators: Zinc oxide (CAS 1314-13-2) 1–5% Magnesium oxide (CAS 1309-48-4) 1–5% Antimicrobial additive 1%: Silver chloride (CAS 7783-90-6) Silver phosphate glass (CAS 308069-39-8) Zinc pyrithione (CAS 13463-41-7) | VQM561L |
The recipe without an antimicrobial additive represents the control.
Table 2.
Chemical composition of the four rubbers tested.
| Main Components | Acronym (In Tables) |
|---|---|
| Ethylene-propylene-diene polymer (CAS 25038-36-2) 35–45% Carbon black (CAS 1333-86-4) 25–35% Residual oils (CAS 64742-01-4) 5–8% Magnesium oxide (CAS 1309-48-4) 1–5% Zinc oxide (CAS 1314-13-2) 0–2% Poly(1,2-dihydro-2,2,4-trimethylquinoline) (CAS 26780-96-1) 0.5–1% bis(tert-butyldioxyisopropyl) benzene (CAS 25155-25-3) 1–2% Triallyl cyanurate (CAS 101-37-1) 0.5–1% | OMCONT |
| Ethylene-propylene-diene polymer (CAS 25038-36-2) 35–45% Carbon black (CAS 1333-86-4) 25–35% Residual oils (CAS 64742-01-4) 5–8% Magnesium oxide (CAS 1309-48-4) 1–5% Zinc oxide (CAS 1314-13-2) 0–2% Poly(1,2-dihydro-2,2,4-trimethylquinoline) (CAS 26780-96-1) 0.5–1% bis(tert-butyldioxyisopropyl) benzene (CAS 25155-25-3) 1–2% Triallyl cyanurate (CAS 101-37-1) 0.5–1% Effectiveness accelerators: Zinc oxide (CAS 1314-13-2) 1–5% Magnesium oxide (CAS 1309-48-4) 1–5% Antimicrobial additive 1%: Silver chloride (CAS 7783-90-6) Silver phosphate glass (CAS-308069-39-8) Zinc pyrithione (CAS 13463-41-7) | NBROM |
| Ethylene-propylene-diene polymer (CAS 25038-36-2) 40–50% Silica gel (CAS 112926-00-8) 15–20% Kaolin (CAS 92704-41-1) 2–6% Carbon black (CAS 1333-86-4) 25–35% Paraffin oil (CAS 97862-82-3) 17–21% Magnesium oxide (CAS 1309-48-4) 0–2% Polyethylene glycol (CAS 25322-68-3) 1–3% Zinc oxide (CAS 1314-13-2) 1–3% Stearic acid (CAS 57-11-4) 0.1–1% 2,2′-Dithiobis(benzothiazole) (CAS 120-78-5) 0.1–1% Tetramethylthiuram Disulfide (CAS 137-26-8) 0.1–1% Rubber Accelerator Zdbc/Bz (CAS 136-23-2) 0.1–1% Sulfur (CAS 7704-34-9) 0.1–1% | CACONT |
| Ethylene-propylene-diene polymer (CAS 25038-36-2) 40–50% Silica gel (CAS 112926-00-8) 15–20% Kaolin (CAS 92704-41-1) 2–6% Carbon black (CAS: 1333-86-4) 25–35% Paraffin oil (CAS 97862-82-3) 17–21% Magnesium oxide (CAS 1309-48-4) 0–2% Polyethylene glycol (CAS 25322-68-3) 1–3% Zinc oxide (CAS 1314-13-2) 1–3% Stearic acid (CAS 57-11-4) 0.1–1% 2,2′-Dithiobis(benzothiazole) (CAS 120-78-5) 0.1–1% Tetramethylthiuram Disulfide (CAS 137-26-8) 0.1–1% Rubber Accelerator Zdbc/Bz (CAS 136-23-2) 0.1–1% Sulfur (CAS 7704-34-9) 0.1–1% Effectiveness accelerators: Zinc oxide (CAS 1314-13-2) 1–5% Magnesium oxide (CAS 1309-48-4) 1–5% Antimicrobial additive 1%: Silver chloride (CAS 7783-90-6) Silver phosphate glass (CAS 308069-39-8) Zinc pyrithione (CAS 13463-41-7) | NBRCA |
The recipe without an antimicrobial additive represents the control.
Table 3.
A comparison of the median survival rates (%) calculated using the Kaplan–Meier method for the silicones with antimicrobial additives (PAAs) vs. controls in both Legionella pneumophila and Salmonella enteritidis.
Table 3.
A comparison of the median survival rates (%) calculated using the Kaplan–Meier method for the silicones with antimicrobial additives (PAAs) vs. controls in both Legionella pneumophila and Salmonella enteritidis.
| Pathogen | Median Survival Rate (%) ± std.err. | Control vs. PAA Added p= | |||||
|---|---|---|---|---|---|---|---|
| CONTROL | VQM105 | ||||||
| L. pneumophila | T1 a | T2 | T3 | T1 | T2 | T3 | |
| 103 CFU/mL | 80 ± 0.53 | 82 ± 0.66 | 15 ± 0.54 | 88 ± 0.41 | 56 ± 0.71 | 0 ± 00 | <0.0001 |
| 104 CFU/mL | 97 ± 0.09 | 60 ± 0.31 | 71 ± 0.40 | 93 ± 0.11 | 58 ± 0.25 | 0 ± 0.00 | <0.0001 |
| S. enteritidis | |||||||
| 103 CFU/mL | 98 ± 0.49 | 70 ± 1.86 | 27 ± 1.82 | 100 ± 0.00 | 86 ± 1.48 | 43 ± 2.61 | <0.0001 |
| 104 CFU/mL | 100 ± 0.00 | 68 ± 0.59 | 36 ± 0.65 | 100 ± 0.00 | 60 ± 0.77 | 0 ± 0.00 | <0.0001 |
| CONTROL | VMQ500D | ||||||
| L. pneumophila | T1 a | T2 | T3 | T1 | T2 | T3 | |
| 103 CFU/mL | 80 ± 0.53 | 82 ± 0.66 | 15 ± 0.54 | 94 ± 0.17 | 71 ± 0.36 | 3 ± 0.16 | <0.0001 |
| 104 CFU/mL | 97 ± 0.09 | 60 ± 0.31 | 71 ± 0.40 | 88 ± 0.08 | 67 ± 0.13 | 5 ± 0.06 | <0.0001 |
| S. enteritidis | |||||||
| 103 CFU/mL | 98 ± 0.49 | 70 ± 1.86 | 27 ± 1.82 | 96 ± 0.19 | 77 ± 0.54 | 14 ± 0.47 | n.s. |
| 104 CFU/mL | 100 ± 0.00 | 68 ± 0.59 | 36 ± 0.65 | 95 ± 0.07 | 85 ± 0.15 | 6 ± 0.11 | n.s. |
| CONTROL | VMQ500L | ||||||
| L. pneumophila | T1 a | T2 | T3 | T1 | T2 | T3 | |
| 103 CFU/mL | 80 ± 0.53 | 82 ± 0.66 | 15 ± 0.54 | 91 ± 0.23 | 76 ± 0.39 | 3 ± 0.17 | <0.0001 |
| 104 CFU/mL | 97 ± 0.09 | 60 ± 0.31 | 71 ± 0.40 | 90 ± 0.07 | 75 ± 0.12 | 3 ± 0.07 | <0.0001 |
| S. enteritidis | |||||||
| 103 CFU/mL | 98 ± 0.49 | 70 ± 1.86 | 27 ± 1.82 | 89 ± 0.32 | 75 ± 0.54 | 5 ± 0.25 | <0.0001 |
| 104 CFU/mL | 100 ± 0.00 | 68 ± 0.59 | 36 ± 0.65 | 91 ± 0.09 | 88 ± 0.14 | 4 ± 0.09 | <0.0001 |
| CONTROL | VMQ561D | ||||||
| L. pneumophila | T1 a | T2 | T3 | T1 | T2 | T3 | |
| 103 CFU/mL | 80 ± 0.53 | 82 ± 0.66 | 15 ± 0.54 | 93 ± 0.20 | 84 ± 0.38 | 2 ± 0.17 | <0.0001 |
| 104 CFU/mL | 97 ± 0.09 | 60 ± 0.31 | 71 ± 0.40 | 93 ± 0.07 | 82 ± 0.13 | 10 ± 0.10 | <0.0001 |
| S. enteritidis | |||||||
| 103 CFU/mL | 98 ± 0.49 | 70 ± 1.86 | 27 ± 1.82 | 93 ± 0.26 | 73 ± 0.53 | 9 ± 0.44 | <0.0001 |
| 104 CFU/mL | 100 ± 0.00 | 68 ± 0.59 | 36 ± 0.65 | 97 ± 0.06 | 66 ± 0.16 | 11 ± 0.21 | <0.0001 |
| CONTROL | VMQ561L | ||||||
| L. pneumophila | T1 a | T2 | T3 | T1 | T2 | T3 | |
| 103 CFU/mL | 80 ± 0.53 | 82 ± 0.66 | 15 ± 0.54 | 100 ± 0.00 | 79 ± 0.57 | 7 ± 0.41 | <0.0001 |
| 104 CFU/mL | 97 ± 0.09 | 60 ± 0.31 | 71 ± 0.40 | 82 ± 0.10 | 85 ± 0.13 | 21 ± 0.13 | <0.0001 |
| S. enteritidis | |||||||
| 103 CFU/mL | 98 ± 0.49 | 70 ± 1.86 | 27 ± 1.82 | 97 ± 0.00 | 91 ± 1.48 | 10 ± 2.61 | <0.0001 |
| 104 CFU/mL | 100 ± 0.00 | 68 ± 0.59 | 36 ± 0.65 | 97 ± 0.06 | 83 ± 0.16 | 17 ± 0.21 | <0.0001 |
a: time post-contact.
Table 4.
A comparison of the median survival rates (%) calculated using the Kaplan–Meier method for the rubber with antimicrobial additives (PAAs) vs. controls in both Legionella pneumophila and Salmonella enteritidis.
Table 4.
A comparison of the median survival rates (%) calculated using the Kaplan–Meier method for the rubber with antimicrobial additives (PAAs) vs. controls in both Legionella pneumophila and Salmonella enteritidis.
| Pathogen | Median Survival Rate (%) ± std.err. | Control vs. PAA Added p= | |||||
|---|---|---|---|---|---|---|---|
| OMCONT | NBROM | ||||||
| L. pneumophila | T1 a | T2 | T3 | T1 | T2 | T3 | |
| 103 CFU/mL | 86 ± 0.40 | 54 ± 0.64 | 0 ± 0.00 | 91 ± 0.37 | 53 ± 0.74 | 0 ± 0.00 | <0.0001 |
| 104 CFU/mL | 71 ± 0.21 | 16 ± 0.17 | 0 ± 0.00 | 87 ± 0.16 | 51 ± 0.26 | 0 ± 0.00 | <0.0001 |
| S. enteritidis | |||||||
| 103 CFU/mL | 93 ± 0.89 | 68 ± 1.93 | 14 ± 1.35 | 81 ± 0.86 | 65 ± 1.15 | 21 ± 0.85 | <0.0001 |
| 104 CFU/mL | 100 ± 0.00 | 62 ± 0.75 | 10 ± 0.42 | 95 ± 0.21 | 82 ± 0.45 | 16 ± 0.46 | <0.0001 |
| CACONT | NBRCA | ||||||
| L. pneumophila | T1 a | T2 | T3 | T1 | T2 | T3 | |
| 103 CFU/mL | 80 ± 0.53 | 82 ± 0.66 | 15 ± 0.54 | 91 ± 0.23 | 83 ± 0.39 | 3 ± 0.17 | <0.0001 |
| 104 CFU/mL | 97 ± 0.09 | 60 ± 0.31 | 71 ± 0.40 | 89 ± 0.07 | 83 ± 0.12 | 5 ± 0.07 | <0.0001 |
| S. enteritidis | |||||||
| 103 CFU/mL | 93 ± 0.89 | 68 ± 1.93 | 14 ± 1.35 | 87 ± 1.02 | 78 ± 1.57 | 11 ± 1.13 | n.s. |
| 104 CFU/mL | 100 ± 0.00 | 62 ± 0.75 | 10 ± 0.42 | 70 ± 0.15 | 52 ± 0.16 | 1 ± 0.02 | <0.0001 |
a: time post-contact; OMCONT and CACONT are untreated controls of NBROM and NBRACA, respectively.
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Tesauro, M.; Sora, V.M.; Meroni, G.; Consonni, M.; Zaghen, F.; Laterza, G.; Martino, P.A.; Zecconi, A. A Pilot Study on Novel Elastomers’ Antimicrobial Activity Against Legionella pneumophila and Salmonella Enteritidis. Appl. Sci. 2025, 15, 5632. https://doi.org/10.3390/app15105632
AMA Style
Tesauro M, Sora VM, Meroni G, Consonni M, Zaghen F, Laterza G, Martino PA, Zecconi A. A Pilot Study on Novel Elastomers’ Antimicrobial Activity Against Legionella pneumophila and Salmonella Enteritidis. Applied Sciences. 2025; 15(10):5632. https://doi.org/10.3390/app15105632
Chicago/Turabian StyleTesauro, Marina, Valerio M. Sora, Gabriele Meroni, Michela Consonni, Francesca Zaghen, Giulia Laterza, Piera Anna Martino, and Alfonso Zecconi. 2025. "A Pilot Study on Novel Elastomers’ Antimicrobial Activity Against Legionella pneumophila and Salmonella Enteritidis" Applied Sciences 15, no. 10: 5632. https://doi.org/10.3390/app15105632
APA StyleTesauro, M., Sora, V. M., Meroni, G., Consonni, M., Zaghen, F., Laterza, G., Martino, P. A., & Zecconi, A. (2025). A Pilot Study on Novel Elastomers’ Antimicrobial Activity Against Legionella pneumophila and Salmonella Enteritidis. Applied Sciences, 15(10), 5632. https://doi.org/10.3390/app15105632
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