The bacteriological quality of hospital-prepared infant feeds

Twenty-four pasteurized infant feeds, prepared in a Glasgow hospital, were examined microbiologically. All produced a satisfactory total aerobic mesophilic count of less than or equal to 1.0x10(4) cfu/g (mean 6.3x10(1) cfu/g) within 1 h of preparation. Bacillus cereus was detected in two infant feeds immediately after preparation and one of these had a B. cereus count of 1.4x10(3) cfu/g exceeding the recommended safety limit of less than or equal to 1.0x10(3) cfu/g. Subsequent storage over a 14h period at 25 degrees C or greater resulted in the appearance of B. cereus in a further eight feeds, the majority of which exceeded the safety limit of 10(3) cfu/g. The microbiological quality of each infant feed depended on the type and number of organisms initially present, and on the temperature and duration of storage. Incubation of feeds at less than or equal to 10 degrees C for 14h did not alter the microbiological quality (P=0.05). While Bacillus licheniformis and Bacillus subtilis were the predominant organisms isolated within 8h of incubation (45.8 and 20.8% of feeds, respectively), additional storage resulted in the emergence of B. cereus I (25%) and II (20.8%) as dominant Bacillus spp. The addition of glucose polymers and other supplements to infant formulae did not affect the type and number of organisms present (P=0.05). Diarrhoeal enterotoxin was detected in three of the five formulations which supported the growth of B. cereus II via the B. cereus enterotoxin reverse phase latex agglutination test BCET-RPLA system. Although the infant feeds were of similar microbiological quality (P=0.05), the majority of Bacillus spp. isolated have been previously implicated in either foodborne illnesses and/or opportunist infections.