Growth, Sporulation, and Germination of Clostridium perfringens in Media of Controlled Water Activity1

Abstract

Requirements in terms of water activity (a,) for the growth, sporulation, and germination of Clostridium perfringens were determined. Strain A48 was used in all phases, and in addition either NCTC 8239 or NCTC 8797 was used for growth, sporulation, and germination studies. The desired a, of the test media was obtained by the addition of one of three solutes: glycerol, sucrose, or sodium chloride. The freezing point depression method was used to determine the a,. The basal medium for growth and germination was Fluid Thioglycollate Medium. It had an a, of 0.995 and produced maximum growth and fastest growth rate among the six levels of a, tested. The lowest a, supporting growth and germination of C. perfringens was between 0.97 and 0.95 in the test media made with sucrose or sodium chloride and 0.93 or below in the test media adjusted with glycerol. Spore production by C. perfringens in Ellner's or modified medium required a higher a, than growth. An understanding of the influence of the available water in foods on the growth, sporulation, and germination of Clostridium perfringens may aid in control of this microorganism as a cause of foodborne illness. The available water activity (a,) in a food is affected by all of the constituents which have an affinity for water. These will include those which can be metabolized by the organism as well as those which cannot. In addition, food processing may alter the available water. Gough and Alford (5) tested the effects of NaCl, NaNO3, and NaNO2 on growth, survival, and heat resistance of several strains of C. perfringens. Growth occurred in concentrations of these salts which were higher than those used in the normal curing of meat. A NaCl concentration of 6% (w/v) in Fluid Thioglycollate Medium was required to inhibit growth significantly. The

The Effect of Water Activity on the Growth and Respiration of Pseudomonas fluorescens

“…The significantly greater inhibition of growth by NaCl or sucrose as compared with that for glycerol at various a, values and over a temperature range at 0.98 a, has been reported for Ps.Juorescens and other bacteria (Marshall et al 1971;Kang et al 1969), yeasts (Brown & Simpson 1972;Horner & Anagnostopoulos 1973) and fungi (Charlang & Horowitz 1971;Horner & Anagnostopoulos 1973). However, the greater inhibition by NaCl than glycerol at equivalent a, only applies to salt-sensitive microorganisms (Marshall el ul.…”

“…For example, halophiles and osmophiles require significant concentrations of solutes for rapid growth. However, for most types of micro-organisms, reductions in a, of the surrounding environment decreases their growth rate (Scott 1957; Pirt 1 9 7 9 , the respiration rate (Christian 1955;Brown 1975), enzyme activity (Baxter & Gibbons 1954: Brown & Simpson 1972, sporulation (Kang et al 1969) and toxin production (Troller 1973). The lowering of a, also increases the permeability of the cell membrane (Charlang & Horowitz 1974) and affects the intracellular composition (Christian & Waltho 1964;Brown 1974).…”

“…However, the assumption that the effect of a, on micro-organisms is independent of the type of solute used to control the a,, does not apply in all cases. Glycerol when used as the controlling solute is less inhibitory to certain micro-organisms than either sucrose or salts at an equivalent a, (Christian 1955;Horner & Anagnostopoulos 1973;Kang et al 1969: Marshall et al 1971). l n this paper, glycerol is shown to inhibit the growth and respiration rates of Ps..fluorescens less than either sucrose or NaCl at similar a, values.…”

The Effect of Water Activity and aw‐Controlling Solute on Sporulation of Bacillus cereus

“…Thus, for this organism the a, requirements for sporulation seem to be very similar to the requirements for vegetative growth. Kang et al (1969), using NaCI, glycerol and sucrose as controlling solutes found that spore production by CZ. perfringens required a significantly higher a, than did growth.…”

ANTIMICROBIAL EFFECTS OF SODIUM AND OTHER IONS IN FOODS: A REVIEW1

“…It is generally advanced that the minimal aw that permits sporulation is similar to or slightly above that for growth, while spore germination may occur even at lower aw(Baird-Parker and Freame 1967 ; Ingram and Kitchell 1967; J . N. SOFOS Kang et al 1969;Troller 1973;1980 Jakobsen andSperber 1983).…”