The Efficiency of Non-Thermal Plasma on the Inhibition of Environmental Isolates of Cryptococcus neoformans from Pigeon Droppings

This study evaluated the antifungal efficacy of a non-thermal plasma (NTP) jet against environmental isolates of Cryptococcus neoformans, a pathogenic fungus commonly found in pigeon droppings and associated with serious infections in immunocompromised individuals. Given the increasing concern over environmental fungal contamination and drug-resistant strains, this research aimed to identify optimized plasma conditions for effective fungal inactivation without relying on chemical disinfectants. Environmental C. neoformans isolates were cultured on Sabouraud dextrose agar and subjected to NTP treatment under systematically varied parameters: input power (30, 50, and 70 W), exposure time (30 s, 1, 2, and 3 min), and air flow rates (1, 1.5, and 2 LPM) mixed with a constant 12 LPM argon gas. Following treatment, plates were incubated at 37°C for 24 hours, and antifungal activity was assessed by measuring the inhibition zone. The highest antifungal effect was achieved at 70 W, with a 3-minute exposure and Ar:Air flow ratio of 12:2 LPM, producing a clear zone of 0.93 ± 0.05 cm². This value corresponded to 28.6% of the inhibition zone produced by the Amphotericin B positive control (3.25 ± 0.08 cm²). All treatment conditions exhibited statistically significant inhibition (p < 0.05), with increased efficacy at higher airflow and longer exposure durations. The generation of reactive oxygen and nitrogen species (RONS) is believed to be the primary mechanism underlying fungal inactivation. These findings demonstrate that Argon-Air-based NTP jet systems offer a promising, eco-friendly, and non-chemical approach for controlling fungal pathogens in environmental settings. The method has potential for application in urban sanitation and public health contexts where fungal contamination from bird droppings poses ongoing risks.