Occurrence of Escherichia coli O157:H7 in hamburgers produced in Brazil.

The occurrence of Escherichia coli O157:H7 was evaluated in 886 samples of hamburgers produced by eight manufacturers in the south and southeast of Brazil from January to September of 1997. The pathogen was not detected in any of the samples analyzed, although 17 (1.9%) showed the presence of E. coli strains, which presented agglutination with O157 antiserum. These strains were not confirmed, since a subsequent identification indicated that they were fermentation positive for sorbitol, incapable of agglutination with the antisera of other commercial brands, and nonproducers of verocytotoxins. A high rate of false-presumptive-positive tests was observed with strains of enterobacteria when isolated by the culture method and when using a commercially purchased enzymatic immunoassay. This high rate of false presumptive positives was likely because the initial screening for sorbitol-negative strains was carried out using phenol red sorbitol 4-methylumbelliferyl-beta-D-glucuronide agar, which was shown to be inadequate for this purpose.

Occurrence and properties of bacteriophages of Leuconostoc oenos in Australian wines.

Bacteriophages specific for Leuconostoc oenos were isolated from four red wines undergoing malolactic fermentation in one winery. Bacteriophages were not found in samples of 16 other wines. The morphology of the phages was examined by electron microscopy. The phages did not lyse all strains of L. oenos, and susceptibility correlated to some extent with the colony morphology of the strain. Phage survived in wines at pH values greater than 3.5 but was inactivated in wines of lower pH and by the addition of sulfur dioxide or bentonite. Phage did not affect the growth of a sensitive strain of L. oenos in filter-sterilized wine.