Impact of the physiological state of fungal spores on their inactivation by active chlorine and hydrogen peroxide

This study aimed at assessing the impact of the physiological state of fungal spores on inactivation by sodium hypochlorite, 0.1% and 0.2% active chlorine, and 3% hydrogen peroxide. In this context, two physiological states were compared for 4 fungal species (5 strains). The first physiological state corresponded to fungal spores produced at 0.99 a(w) and harvested using an aqueous solution (laboratory conditions), while the second one corresponded to fungal spores produced under a moderate water stress (0.95 a(w)) and dry-harvested (mechanical harvesting without use of any water, mimicking food plant conditions). Aspergillus flavus food plant conidia were more resistant to all tested fungicide molecules than the laboratory ones. The same phenomenon was observed for Penicillium commune UBOCC-A-116003 conidia treated with hydrogen peroxide. However, this isolate did not exhibit any inactivation difference between laboratory and food plant conidia treated with sodium hypochlorite. Similarly, the physiological state of Cladosporium cladosporioides conidia did not impact the efficacy of the tested biocides. P. commune UBOCC-A-112059 food plant and laboratory conidia were more resistant to hydrogen peroxide and sodium hypochlorite, respectively. As for Mucor circinelloides, laboratory spores were more resistant to all disinfectant than the food plant ones. Noteworthy, regardless of the physiological state, all M. circinelloides and C. cladosporioides conidia were inactivated for 5 min treatment at 0.2% active chlorine and for 2.5 min treatment at 0.1% active chlorine, while the conidia of all the other species remained viable for these treatments. The obtained data indicate that the efficacy of disinfectant molecules depends not only on the encountered fungal species and its intraspecific diversity but also on the spore physiological state.

Automated summary

This study aimed to evaluate the impact of the physiological state of fungal spores on the efficacy of various disinfectant molecules. The results indicate that the effectiveness of disinfectants depends on the encountered fungal species, its intraspecific diversity, and the spore physiological state.