No abstract

The composition of the insoluble "integuments" and soluble "contents" fractions of spores of four Bacillus species of widely differing heat resistance were compared. Electron microscopy of thin sections was also used to determine and compare the morphological structures in the integument preparations. The soluble fractions of the thermophiles, B. coagulans and B. stearothermophilus, had a higher content of hexose and dipicolinic acid. The hexose content of both fractions of the four species was related to heat resistance. Integument fractions consisted chiefly of protein together with variable amounts of the mucopeptide constituents, a, e-diaminopimelic acid (DAP) and hexosamine. In the thermophiles the DAP and hexosamine were found chiefly in the insoluble integuments fractions, while in B. cereus and B. subtilis most of this material was soluble. Integument preparations, containing mainly protein with little mucopeptide, consisted chiefly of outer and inner spore coats, while preparations having more mucopeptide contained also residual cortical material and a cortical membrane (possibly the germ cell wall). The results suggest that spore integuments consist of mainly proteinaceous outer and inner coats together with variable amounts of residual cortex and cortical membrane which contain the mucopeptide material.

Summary. Faecal samples from 123 infants who died with sudden infant death syndrome (SIDS) and from a comparative group of 52 age-matched babies were analysed for toxigenic bacteria and their toxins. Serum samples from the SIDS infants were also analysed for these toxins. A significantly higher proportion of toxigenic bacteria and their toxins were found in faecal samples of SIDS babies than in samples from the comparative group. These toxins were also found in serum from the SIDS babies. Formula-fed SIDS babies had a significantly higher incidence of C. dzgicile k2 = 6.654, p < 0-Ol), C. perfringens k2 = 6-422, p < 0.05), and its enterotoxin k2 = 7.787, p < 0.01) in faeces, and a higher incidence (non-significant) of C. perfringens enterotoxin in their serum, faecal HLML toxin, and S. aureus and its enterotoxin, than breast-fed babies. Male SIDS babies had a significantly higher incidence of C. perfringens k2 = 7.687, p < 0-01) and higher incidences (non-significant) of C. perfringens enterotoxin, HLML toxin, C. dzgicile, and S. aureus and its enterotoxin than female babies. SIDS babies dying in winter had a significantly higher incidence of C. dzgicile than those dying in summer k2 = 5.328, p < 0-05) and spring 01' = 4.444, p < 0.05). C. perfringens, S. aureus and their enterotoxins occurred in more babies dying in autumn and winter than in spring and summer. The incidence of these bacteria and their toxins did not differ for position of death. These results provide some support for the idea that intestinal toxins have a pathogenic role in SIDS.

SUMMARYThe heat resistance of the spores of six species of bacteria varied with water activity (a,) at which the spores were heated, although the magnitude of the changes differed greatly between species. At all a, values there was an approximately linear relation between the logarithm of the number of viable spores and the time of heating. The slopes of these straight lines were used to describe the observed death-rates as the time ( D value) required to decrease the population by one log. unit. For all six species the greatest heat resistance was manifest at a, values of about 0.2-0.4, the maximum D values at 110' varying from about 2 to 24 hr. A t a, values less than 0.2 the heat resistance decreased; for spores rigorously dried over P,O, (0.00 a,) the D values at 110" now varied between about 30sec. and 30min. When the spores were heated a t a, values above 0.4 the resistance of 4 species decreased considerably, being lowest at 1-00 a,; with spores of Bacillus coagulans and B. stearothermophilus the heat resistance decreased less at the high a, values; at 1.00 a, their D values were slightly greater than at 0.00 a,. At the high a, values the D values a t 110' varied from less than 0.1 sec. for Clostridium botulinum type E to about 40 min. for B. coagulans and B. stearothermophiZus. The Qlo for thermal death was about 10 at high a, values, decreasing to about 2 at a, values below 0-3. Under very moist conditions spores of B. stearothermophilus were about 50,000 times more heat resistant than were spores of C . botulinum type E ; but at a, values less than about 0.5 this ratio fell to about 10. The convergence of this ratio resulted from more than a 100,OOo-fold increase in the resistance of the type E spores, and only a 20-fold increase in the resistance of the spores of B. stearothermophilus.

SUMMARYThe heat resistance of the spores of six species of bacteria varied with water activity (a,) at which the spores were heated, although the magnitude of the changes differed greatly between species. At all a, values there was an approximately linear relation between the logarithm of the number of viable spores and the time of heating. The slopes of these straight lines were used to describe the observed death-rates as the time ( D value) required to decrease the population by one log. unit. For all six species the greatest heat resistance was manifest at a, values of about 0.2-0.4, the maximum D values at 110' varying from about 2 to 24 hr. A t a, values less than 0.2 the heat resistance decreased; for spores rigorously dried over P,O, (0.00 a,) the D values at 110" now varied between about 30sec. and 30min. When the spores were heated a t a, values above 0.4 the resistance of 4 species decreased considerably, being lowest at 1-00 a,; with spores of Bacillus coagulans and B. stearothermophilus the heat resistance decreased less at the high a, values; at 1.00 a, their D values were slightly greater than at 0.00 a,. At the high a, values the D values a t 110' varied from less than 0.1 sec. for Clostridium botulinum type E to about 40 min. for B. coagulans and B. stearothermophiZus. The Qlo for thermal death was about 10 at high a, values, decreasing to about 2 at a, values below 0-3. Under very moist conditions spores of B. stearothermophilus were about 50,000 times more heat resistant than were spores of C . botulinum type E ; but at a, values less than about 0.5 this ratio fell to about 10. The convergence of this ratio resulted from more than a 100,OOo-fold increase in the resistance of the type E spores, and only a 20-fold increase in the resistance of the spores of B. stearothermophilus.