Effects of High-Pressure Treatment on Spores of Clostridium Species

Abstract

This work analyzes the high-pressure (HP) germination of spores of the food-borne pathogen Clostridium perfringens (with inner membrane [IM] germinant receptors [GRs]) and the opportunistic pathogen Clostridium difficile (with no IM GRs), which has growing implications as an emerging food safety threat. In contrast to those of spores of Bacillus species, mechanisms of HP germination of clostridial spores have not been well studied. HP treatments trigger Bacillus spore germination through spores' IM GRs at ϳ150 MPa or through SpoVA channels for release of spores' dipicolinic acid (DPA) at >400 MPa, and DPA-less spores have lower wet heat resistance than dormant spores. We found that C. difficile spores exhibited no germination events upon 150-MPa treatment and were not heat sensitized. In contrast, 150-MPa-treated unactivated C. perfringens spores released DPA and became heat sensitive, although most spores did not complete germination by fully rehydrating the spore core, but this treatment of heat-activated spores led to almost complete germination and greater heat sensitization. Spores of both clostridial organisms released DPA during 550-MPa treatment, but C. difficile spores did not complete germination and remained heat resistant. Heat-activated 550-MPa-HP-treated C. perfringens spores germinated almost completely and became heat sensitive. However, unactivated 550-MPa-treated C. perfringens spores did not germinate completely and were less heat sensitive than spores that completed germination. Since C. difficile and C. perfringens spores use different mechanisms for sensing germinants, our results may allow refinement of HP methods for their inactivation in foods and other applications and may guide the development of commercially sterile low-acid foods. IMPORTANCESpores of various clostridial organisms cause human disease, sometimes due to food contamination by spores. Because of these spores' resistance to normal decontamination regimens, there is continued interest in ways to kill spores without compromising food quality. High hydrostatic pressure (HP) under appropriate conditions can inactivate bacterial spores. With growing use of HP for food pasteurization, advancement of HP for commercial production of sterile low-acid foods requires understanding of mechanisms of spores' interactions with HP. While much is known about HP germination and inactivation of spores of Bacillus species, how HP germinates and inactivates clostridial spores is less well understood. In this work we have tried to remedy this information deficit by examining germination of spores of Clostridium difficile and Clostridium perfringens by several HP and temperature levels. The results may give insight that could facilitate more efficient methods for spore eradication in food sterilization or pasteurization, biodecontamination, and health care.

Killing of bacterial spores by dodecylamine and its effects on spore inner membrane properties

“…However, with spores of at least Clostridioides difficile , CaDPA release does not trigger completion of spore germination, although the CaDPA‐less spores have a higher core water content and are less wet heat resistant than dormant spores (Doona et al . 2016; Setlow et al . 2017).…”

Continuous Versus Discontinuous Ultra‐High‐Pressure Systems for Food Sterilization with Focus on Ultra‐High‐Pressure Homogenization and High‐Pressure Thermal Sterilization: A Review

“…Under these conditions the main inactivation force is the temperature (Reineke et al., ; Sevenich et al., ). Recently, the differences in germination under pressure between Clostridium spores and Bacillus spores have been revealed, showing interesting insights (Figure ; Doona et al., ; Lenz & Vogel, ; Paredes‐Sabja, Setlow, & Sarker, ). In Bacillus spp ., DPA release triggers cortex lytic enzyme (CLE) activation; CLE action is not essential for DPA release, but it can accelerate it.…”

“…In Clostridium difficile or Clostridium perfringens Doona et al. () observed that the inactivation mechanism differs in comparison to Bacillus species. For the tested strains the initiation of cortex hydrolysis by SleC precedes and triggers DPA release.…”

“…However, without heat activation these spores could not complete germination. DPA was released by both clostridial spores at 550‐MPa, but no complete germination for C. difficile spores could be attained and the spores remained heat resistant (Doona et al., ).…”

Evaluation of thermal destruction kinetics of Clostridium difficile spores (ATCC 17857) in lean ground beef with first‐order/Weibull modeling considerations

“…Therefore, they reported that heating of food to temperatures above 85 C would be necessary to inactivate viable spores of C. difficile. More recently, Redondo-Solano, Burson, and Thippareddi (2016) reported much higher thermal resistance for three hypervirulent and one nonvirulent strains of C. difficile spores ranging from 22.14 h at 70 C to 4.93 min at 70 to 90 C. Microwave heating (Malyshev, Williams, Lees, Baillie, & Porch, 2019;Ojha et al, 2016), high pressure treatment (Doona et al, 2016), and use of electrolyzed water (Tkhawkho, Jackson, Nitzan, & Peretz, 2017) have also been proposed for destruction of C. difficile spores.…”