Antimicrobial efficacy and potential application of a newly developed plasma-based ultraviolet irradiation facility

A low-pressure mercury vapour discharge tube generating high-intensity ultraviolet (UV) resonance radiation at 254 nm was designed to achieve a nearly simultaneous all-round UV irradiation of products. Testing this 'universal homogeneous ultraviolet (UHUV) irradiation facility' with suspended Bacillus subtilis spores, resulted in a 10(6)-fold reduction in viable count within 30 s applying irradiation energy of 0.3 mW/cm(2). Moreover, this irradiation dose reduced the number of immobilized B. subtilis spores on several material surfaces (wood-free paper, aluminium foil, polystyrol, polypropylene, and polyethylene foil) 10(2)-10(4)-fold. To evaluate potential applications of this UHUV irradiation technique under more realistic conditions, dental hand pieces and orthodontic forceps were contaminated by a blood-saliva mix containing Staphylococcus aureus. Under these conditions, a reduction in viable count of 10(5)-10(6)-fold was achieved within 5-15 min, but higher irradiation energy levels up to 13 mW/cm(2) were necessary. Because of its construction, the shape of the newly developed UHUV irradiation device can be adapted to various shapes to achieve a fast and effective antimicrobial treatment.