RESUMO
The antibacterial activity of the hexane, ethyl acetate and methanol extracts of the flowers, leaves and stems of Gnaphalium oxyphyllum var. oxyphyllum, G. liebmannii var. monticola and G. viscosum was investigated. The hexane extracts showed in all cases the higher inhibitions, G. oxyphyllum flower extract exhibiting the wider spectrum of activity.
Assuntos
Antibacterianos/farmacologia , Asteraceae , Bactérias/efeitos dos fármacos , Extratos Vegetais/farmacologia , Diterpenos/farmacologia , Flavonoides/farmacologia , Humanos , Testes de Sensibilidade Microbiana , Folhas de Planta/química , Caules de Planta/químicaRESUMO
The ability of a yogurt starter culture formed by Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp bulgaricus to inhibit the growth of four enterotoxin type A and B producers Staphylococcus aureus strains (ATCC 6538, S6, FRI-100 and a strain isolated from milk) during fermentation of milk and subsequent storage was investigated. Sterile skim milk was inoculated with about 10(6) CFU/ml of S. aureus and with about 10(6) CFU of starter culture, and incubated at 42 degrees C during 8 h, followed by refrigeration at 4 degrees C. Samples were taken every 2 h during fermentation and every 2 days during storage. Viable count of lactic acid bacteria and S. aureus as well as pH, acidity, thermostable deoxyribonuclease (TNase) and staphylococcal enterotoxin A (SEA) production were evaluated. Behavior of four strains was similar; S. aureus survived the 8 h fermentation with LAB, and its population began to decrease from the first day of storage, being completely inhibited at 9-10 days. TNase and SEA production were positive in all samples taken along the study. It was demonstrated that enterotoxigenic strains of S. aureus were able to survive the fermentation of milk with a yogurt starter culture and they were inhibited after several days during storage of the fermented product, contrary to the general belief which considered it very difficult due to the low pH. Even though S. aureus was inhibited, TNase and SEA were demonstrable along the storage. Therefore, fermented milks may play an important role in the transmission of this organism.
Assuntos
Enterotoxinas/biossíntese , Lactobacillus/fisiologia , Leite/microbiologia , Staphylococcus aureus/crescimento & desenvolvimento , Streptococcus/fisiologia , Iogurte/microbiologia , Animais , Fermentação , Conservação de Alimentos , Concentração de Íons de Hidrogênio , Nuclease do Micrococo/análise , Intoxicação Alimentar Estafilocócica/transmissão , Staphylococcus aureus/metabolismo , Fatores de TempoRESUMO
The purpose of this research was to determine the survival of Listeria monocytogenes in sterile skim milk during the fermentation with a yogurt starter culture and during storage at refrigeration temperature. Sterile skim milk was inoculated with 10(3), 10(5) and 10(7) cfu/ml of L. monocytogenes and with 10(6) cfu of lactic acid bacteria. Inoculated milks were fermented for 8 h at 42 degrees C, followed by refrigeration at 4 degrees C. Samples were taken at 2 h intervals during fermentation and at 2 days intervals during storage. Acidity and pH were measured, as well as viable count of lactic acid bacteria and pathogen. L. monocytogenes survived 8h, 10 days and 32 days in the fermented milk, when the inocula were 10(3), 10(5) and 10(7) cfu/ml, respectively. Inhibition of the pathogen was associated with a decrease of pH below 4.0 and increase in acidity. It was demonstrated that this pathogen is able to survive several weeks in milk fermented with a starter culture, contrary to the general belief which considered it very difficult due to the low pH. Therefore fermented milks may play an important role in the transmission of these bacteria.