Applicazione e valutazione di sistemi per la sanificazione in ambienti indoor a ridotto impatto ambientale

The present thesis aimed to evaluate the efficacy of devices, with reduced environmental impact, for biological sanitization of air and surfaces in indoor environments, gave rise to new evidence about the use of UV-C technology. The sanitizing efficacy of two UV-C LED devices was investigated. The first tested system, CSA System S14000, was installed in a university sports pressostatic structure. The sanitization efficacy of the device (which sanitizes up to 19000 m3/h of air) in its entire configuration, and of each single component was assessed following the procedures reported by the ISO 15714:2019. Second, the sanitization efficiency of the device was evaluated through on-site environmental tests in presence of athletes. The results showed high efficacy in eliminating airborne microorganisms, both during efficacy tests (inactivation rate around 99.92 ± 0.07%, log reduction of 3.22 ± 0.39) and in on-site environmental tests (inactivation rate around 70.7 ± 3.6% and 72.4 ± 3.3% for airborne bacteria and molds, respectively). The CSA System S14000 is a promising solution to guarantee efficient and healthy sanitation for athletes during sporting activity. Furthermore, the efficacy of a UV-C LED hand lamp, designed for surface disinfection in domestic or small-scale food-processing environments, was evaluated through in vitro decontamination tests using standard ATCC microorganisms, with different UV-C susceptibility (E. coli ATCC 25922, B. subtilis ATCC 6633, Cladosporium spp.). A bacterial titer <1 CFU/mL was achieved by applying a UV dose of 15.55 and 21.77 mJ/cm2, while against Cladosporium spp, an inactivation of 50 ± 14.14% was achieved with a higher UV dose (31.1 mJ/cm2). Then, the device disinfection efficacy in decontamination of stainless steel (SS), polypropylene (PP), and glass surfaces was assessed using four different foodborne bacterial isolated strains, after assessing individual UV-susceptibility. The results showed a different microbial inactivation on the three surfaces. On both SS and glass, a titer of <1 CFU/169 cm2 was achieved against all the isolated bacterial strains applying the highest UV dose, except with L. monocytogenes 1484. Despite this, lower microbial inactivation was obtained on PP. The use of a UV-C LED hand lamp could be an efficient disinfection method to reduce the cross-contamination of food. As well as the type of surface material, another factor that could reduce the UV-C irradiation efficacy is the presence of biofilm. Considering this, the UV-C irradiation (254nm) efficacy in inactivating microorganisms of hospital interest in a mature biofilm was assessed both in vitro and on SS discs. A UV dose of 946.7 mJ/cm2 was enough to reduce the bacterial load by 4.34 ± 0.70, 4.70 ± 0.60, and 4.85 ± 0.98 log10 units against MSSA ATCC 29213, MRSA ATCC 43300, and MRSE (isolated strain), respectively. Against gram negative bacteria biofilm, a UV dose of 467.8 mJ/cm2 was enough to achieve a microbial titer <1 CFU/mL. C. albicans ATCC 14053 showed higher UV resistance in a biofilm state (3.17 ± 0.08 log reduction). Regarding the 24h-biofilm on discs, applying a UV dose of 946.7 mJ/cm2 a microbial titer <1 CFU/mL was achieved against E. coli, while a log reduction >3 logs was achieved with all other microorganisms. Lastly, the ability of UV-C irradiation to induce a VBNC state in E. coli was investigated. The positivity of UV-treated culture-negative samples to enzymatic and resuscitation tests would indicate the possible presence of VBNC cells.