In vitro growth control of selected pathogens by Lactobacillus acidophilus- and Lactobacillus casei-fermented milk.

AIMS: Food-borne pathogen inhibition was tested in the presence of a mixture of Lactobacillus acidophilus and Lactobacillus casei during fermentation under controlled pH conditions. METHODS AND RESULTS: The growth of Escherichia coli O157:H7, Salmonella serotype Typhimurium, Staphylococcus aureus, Listeria innocua, Enterococcus faecium and Enterococcus faecalis was evaluated for 48 h at 37 degrees C. In the presence of the lactic acid bacteria (LAB), an increase of the generation time was observed for all the gram-positive bacteria evaluated. Staphylococcus aureus was the most sensitive strain showing an increase of the generation time by 210%. However, for all the gram-negative bacteria evaluated, no inhibition occurred after 8 h of fermentation. The soluble portion of Lact. acidophilus- and Lact. casei-fermented milk was recuperated and tested for its antimicrobial activity. Listeria innocua and Staph. aureus were the most sensitive to the presence of fermented milk supernatant showing an inhibition of 85.9% and 84.7%, respectively. This soluble fraction was neutralized to eliminate the antimicrobial effect of the organic acids produced; the most sensitive strains were L. innocua and E. coli O157:H7 showing an inhibition of 65.9% and 61.9%, respectively. Finally, the soluble fraction was neutralized and irradiated at 45 kGy using a (60)Co source to eliminate the possible antimicrobial effect of both organic acids and bacteriocin-like substances. Enterococcus faecalis, E. coli O157:H7 and Staph. aureus were the most affected bacteria by this fraction, showing 39.1, 32 and 31.2% inhibition, respectively. CONCLUSIONS: The results obtained in this study suggest the implication of both organic acids and bacteriocin-like inhibitory substances in the antimicrobial activity observed in the soluble fraction of the probiotic preparation. SIGNIFICANCE AND IMPACT OF THE STUDY: This study revealed the antimicrobial mechanisms of action of Lact. acidophilus- and Lact. casei-fermented milk used to prevent antibiotic-associated diarrhoea.

[Incidence of UV rays on nutritional elements of baby foods according to the nature of the wrapping: white and dark glass]. / Etude expérimentale de l'incidence des rayons U.V. sur les éléments nutritionnels des "baby-foods" selon la nature du conditionnement: verre blanc-verre brun.

Drawing the inference from their experiment the authors have both pointed out the baneful influence of light on evolution of some vitamins and proved that the filter power of tinted packing is an important factor in this test mechanism: --vitamin C has a light development in an atmosphere without oxygen and is more sensitive about temperature than about light; --vitamin A is sensitive about both light and temperature. U.V. radiation applied to a product whose temperature is higher than 20 degrees C causes more damage to this product when packing is made of transparent glass; --the protector power of stained glass is still more obvious in vitamin B2.

[Pollution of human milk in France by organochlorine insecticide residues]. / La pollution des laits humains français par les résidus d'insecticides organochlorés

The monthly analysis of milk mixtures from ten French human milk banks, over a period of two years, showed that there was marked pollution by organochlorine insecticide residues. The following averages were noted: hexachlorocyclohexane + hexachlorobenzene 2,75 mg/kg of pure fat, DDT and derivatives 3,24 mg/kg fat, heptachlor epoxide 0,28, dieldrin 0,23. The main insecticides were, with average values, beta hexachlorocyclohexane (1,67), hexachlorobenzene (0,98), and dichlorodiphenyldichloroethylene (2,40). All these milks were invariably very polluted throughout the year, but there were however noted some qualitative differences according to the geographic position of the milk banks: South of the Loire river, the main polluting factor was hexachlorocyclohexane, whilst North of the Seine, fairly high values were found for heptachlor epoxide and dieldrin. The special study of human milk from Lille showed a 50% reduction in pollution between 1970 and 1973. The probable routes of contamination are human food and the ill-advised domestic use of pesticides.