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In investigations on three outbreaks of Bacillus cereus food poisoning in Spain and The Netherlands, the causative strains grew within a temperature range of 4-37 degrees C, but not at 43 degrees C. Such psychrotrophic types were found to occur in various dairy products (including ca 25% of 35 samples of pasteurized milk) and some mousses and cook/chill meals. Growth of and enterotoxin production by psychrotrophic B. cereus could be prevented by temperatures below 4 degrees C and pH-values not exceeding 5.0.

Chapman's medium designed for the enumeration of Staphylococcus aureus showed three shortcomings: (i) micrococci and many Bacillus spp. grow well on this agar and may obscure colonies of Staph. aureus; (ii) some strains of Staph. aureus fail t o dissimilate mannitol; among 1164 strains examined, mostly from clinical sources, 4.4 yo appeared unable to dissimilate mannitol; (iii) the agar has inhibitory properties to sublethally impaired cells of Staph. uureus. The latter deficiency not being correctable, the suitability of the egg yolk-tellurite-glycine-pyruvate agar (ETGPA) of Baird-Parker (1962b) was evaluated. Of 522 strains of Staph. aureus of human and food origin 97.5 yo developed characteristically and generally quantitatively on Baird-Parker's agar.Raird-Parker's medium has proved valuable in ecological studies on the occurrence and development of Staph. aureus in foods incriminated in staphyloenterotoxicosis : among 165 atypical black colonies isolated from 450 food samples only 2% were Staph. aureua.