Persistence of vegetative and sporulated forms of Clostridium perfringens exposed to air at different relative humidities

C. perfringens, an anaerobic bacterium, is a common cause of food poisoning that can persist on surfaces in slaughterhouses. However, the mechanisms governing its survival in such environments - characterised by variations in relative air humidity (RAH) - remain poorly understood. This study aimed to evaluate the effect of air exposure on C. perfringens survival and to identify the mechanisms responsible for its inactivation. Vegetative cells and spores of C. perfringens were deposited on inert surfaces and exposed to different RAH (11 %, 43 %, 75 %, 100 %) under both aerobic and anaerobic conditions, to assess the contributions of osmotic and oxidative effects induced by dehydration to cell death. At low RAH, more than 99 % of vegetative cells were inactivated within one day, regardless of oxygen presence. Epifluorescence microscopy and flow cytometry analyses revealed that dehydration and rehydration disrupted membrane integrity, contributing to inactivation through lethal mechanical damage. At 100 % RAH, vegetative cells survived over 3 days under aerobic conditions (>1 %) and over 30 days under anaerobic conditions (>0.003 %). The composition of the dehydration medium had little effect on cell survival. In contrast, spores were much more resistant, with around 10 % survival after two months of stress in presence of oxygen, without any significant effect of dehydration. These results highlight the potential of exploiting RAH fluctuations to develop control strategies targeting C. perfringens vegetative cells. However, the extreme resilience of spores confirms the need for specific and targeted decontamination methods to eliminate them effectively.