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The ability of Campylobacter jejuni ATCC 11168 to survive on beef and pork stored under chilled, vacuum packaged and retail display conditions were examined. In addition, the effect of natural microflora on commercial beef and pork on the survival of C. jejuni under these storage conditions was examined. When sterile cores of beef and pork were inoculated with ∼ 10(5) to 10(6) cfu cm(-2)C. jejuni, and were stored under aerobic or vacuum packaged conditions at -1.5 or 4 °C, its numbers dropped significantly and C. jejuni could not be enumerated by direct plating after 21 d of the 6 wks study. In contrast, survival of C. jejuni on commercial vacuum packaged beef and pork was significantly enhanced, resulting in only 1 log cfu cm(-2) reduction at the end of 6 wks. During 7 d of display in a retail case, numbers of C. jejuni dropped quickly, but could be enumerated by direct plating even after the 7 d. The presence of high numbers of inoculated C. jejuni on beef and pork had no significant effect on the natural microflora numbers compared to uninoculated controls when the meat was stored either in vacuum or in a retail display case. These results show that natural microflora on vacuum packaged meat afford enhanced survival of C. jejuni present on the surfaces of both beef and pork when stored at refrigeration temperatures. Hence, strict hygienic practices or the implementation of decontamination technologies are recommended to ensure safety of meat with respect to this pathogen.

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A new bacteriophage (phage ggg) and its host, Leuconostoc gelidum LRC-BD, were isolated from vacuum-packaged pork loins. Homogenates of pork loin tissue were enriched with L. gelidum LRC-BD to isolate phages. Cultural, biochemical and genetic methods were used to compare L. gelidum LRC-BD and the type strain, L. gelidum ATCC 49366. The phages were characterized by host range, morphology and phage-bacterial interaction in All Purpose Tween (APT) broth and on pork adipose tissue. With the exception of its inability to produce dextran from sucrose and the fermentation of l-arabinose, L. gelidum LRC-BD was culturally and biochemically similar to L. gelidum ATCC 49366. DNA-relatedness of the strains was confirmed by sequencing of the 16s rRNA gene. Electron microscopic observation revealed that phage ggg was a member of the Siphoviridae. The host range was limited to L. gelidum isolates from meats. Phages were able to replicate and limit the growth of L. gelidum LRC-BD in APT broth incubated aerobically and anaerobically at 4 degrees C, with a multiplicity of infection (MOI) of 0.001. When inoculated pork adipose tissue was stored at 4 degrees C in air or vacuum, phages could multiply but a higher MOI (0.01 to 1000) was necessary to limit the growth of L. gelidum LRC-BD. Naturally occurring phages may affect the numbers of L. gelidum and other lactic acid bacteria residing in meats and thereby alter the storage quality or the preservative potential of competitive strains.

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The effect of a bacteriocinogenic Brochothrix campestris ATCC 43754 upon the growth of Brochothrix thermosphacta and a 4 strain mixture of Listeria monocytogenes was determined in All Purpose Tween (APT) broth and on pork adipose tissue discs at 4 degrees C. Inocula were prepared to give initial numbers of B. campestris of 6-7 log cfu/ml or cm(2) and 3-4 log cfu/ml or cm(2) of B. thermosphacta and L. monocytogenes. Adipose tissue discs were evaluated by a sensory panel to determine the intensity and acceptability of any off-odours produced during the growth of B. campestris. During co-culture in APT broth with B. campestris the growth of B. thermosphacta or L. monocytogenes was 4 log cycles less than growth in its absence. B. campestris showed limited growth on inoculated pork adipose tissue, increasing from initial numbers of about 6 log cfu/cm(2) to a maximum of 7 log cfu/cm(2) within 7d. B. campestris at numbers of 7 log cfu/cm(2) produced slight off-odours but these were not perceived by the panel as unacceptable. When co-inoculated on adipose tissue discs with B. campestris the numbers of B. thermosphacta or L. monocytogenes was limited to about 2-3 log units less than the numbers attained in its absence. B. campestris ATCC 43754 may be useful for meat preservation because it can inhibit B. thermosphacta and L. monocytogenes in situ while producing little change in the sensory properties of the product.

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Adipose tissue discs were coinoculated with Brochothrix thermosphacta and homologous bacteriophages (phages) to determine the effects these had on phage multiplication, bacterial growth, and off-odor development during storage at 2 degrees C or under simulated retail display at 6 degrees C. In the presence of about 10(5) bacteria/cm2 and an equivalent number of phages, there was a 3-log increase in phage numbers and a 2-log decrease in bacterial numbers, and objectionable off-odors were suppressed during refrigerated storage. Up to 68% of the surviving bacterial population were resistant to phages. The storage life of adipose tissue could be increased from 4 days in controls to 8 days in phage-treated samples by preventing the development of off-odors associated with the growth of B. thermosphacta. Phages may provide a novel approach to extending the storage quality of chilled meats.

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Hydrophobic grid membrane filtration (HGMF) was investigated as an alternative to conventional plate counts for enumerating spoilage bacteria recovered from raw beef. The HGMF method was compared to conventional procedures for the selective enumeration of total psychrotrophic bacteria, pseudomonads, total Enterobacteriaceae . Brochothrix thermosphacta , and lactic acid bacteria. Bacteria were recovered both from beef which had been artificially inoculated with identified strains and from naturally contaminated beef from a commercial abattoir. There were no significant differences (P > 0.05) in numbers of any bacterial group recovered from naturally contaminated beef using HGMF procedures when compared to conventional plating on selective media. The recoveries of the total psychrotrophic population, Escherichia coli . B. thermosphacta , and Lactobacillus sake inoculated onto meat were unaffected by the enumeration procedure (P > 0.05). However, the populations of Pseudomonas sp. recovered from inoculated beef by a HGMF procedure were 0.8 log cycles lower (P < 0.05) when compared to the conventional spread plate procedure.