Sensitivity of Foodborne Bacteria (Spoilage and Pathogenic) to a Methanol-Acetone Extract of Milk Fermented by Streptococcus thermophilus

Abstract

Effects of an inhibitory methanol-acetone (MA) extract of Streptococcus thermophilus-fermented milk was tested on growth of Salmonella enteritidis, two strains of Staphylococcus aureus (types A and E), two strains of Clostridium perfringens (types A and C) and Pseudomonas fluorescens. Each organism was tested at three levels of the extract, e.g., 250, 500 and 1000 ppm. Results indicated that the degree of sensitivity among the test organisms varied. C. perfringens (C) was the most sensitive, with a mean % inhibition (average % inhibition over the three MA extract concentrations) of 73.3, while S. enteritidis was the least sensitive (mean % inhibition = 51.8) to the extract. The differences between the mean % inhibition of P. fluorescens (65.4), S. aureus (A) (64.8), and C. perfringens (A) (62.2) were not significant (P>0.05); however, the sensitivity of these three organisms to the extract was significantly less (P<0.05) than C. perfringens (C) but significantly greater (P<0.05) than S. aureus (E) and S. enteritidis.