We investigated involvement of feral swine in contamination of agricultural fields and surface waterways with Escherichia coli O157:H7 after a nationwide outbreak traced to bagged spinach from California. Isolates from feral swine, cattle, surface water, sediment, and soil at 1 ranch were matched to the outbreak strain.

A protease-sensitive antibacterial substance, produced by a strain of Lactobacillus plantarum isolated from fermented corn, was classified as a bacteriocin and designated plantaricin KW30. The bacteriocin was stable to heat, pH and treatment with surfactants, and unaffected by a-amylase, lipase or lysozyme. Plantaricin KW30 exhibited a bactericidal and non-bacteriolytic mode of action againstindicator cells, and inhibitory activity was limited to other lactobacilli. Maximum production was in MRS broth, and coincided with the onset of stationary phase under conditions of low pH and high cell numbers. In a complex medium bacteriocin production was enhanced by the presence of sodium acetate and Tween 80. Curing experiments gave derivatives that no longer produced the bacteriocin but retained immunity to it. These Bac-derivatives showed the same plasmid pattern as the parent strain suggesting a chromosomal location for the genes for bacteriocin production.

Pulsed-field gel electrophoresis of chromosomal DNA digested with NotI or SfiI was used to differentiate individual strains of Leuconostoc oenos. L. oenos isolates with 13 different restriction digest patterns were detected in New Zealand wines undergoing malolactic fermentation. The average genome size was estimated to be 1,800 kb. In cool-climate wine-growing regions, such as New Zealand, malolactic fermentation (MLF) has a significant role in wine quality. In this fermentation, lactic acid bacteria convert L-malic acid from grapes to L-lactic acid and CO2, thus reducing the acidity of the wine (11). These bacteria also influence wine flavor and aroma (17). Leuconostoc oenos is the organism considered preferable for achieving MLF in wine because of its tolerance to low pH and high ethanol levels (11). Several strains of L. oenos may occur in a single fermentation (6); and with increasing use of L. oenos starter cultures in wine making, especially if strains with particular flavor characteristics become available (8), a method for accurately identifying L. oenos strains will be required to monitor the survival and contribution of inoculated and indigenous bacteria. The aim of this work was to determine whether pulsed-field gel electrophoresis (PFGE) patterns of restriction enzyme-digested chromosomal DNA could be used to differentiate individual strains of L. oenos. The L. oenos reference strains used in this study were NCFB 1674,

No abstract

No abstract