Quantitative Recovery of Listeria monocytogenes and Salmonella enterica from Environmental Sampling Media
Bazaco, Michael Constantine
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Environmental sampling is a pathogen monitoring technique that has become important in the food industry. Many food processing companies have adopted environmental sampling as a way to verify good manufacturing practices and sanitation plans in their facilities. Environmental sampling is helpful because it gives better information on the source of product contamination than end product sampling. Two specific pathogens of concern to the food industry are Listeria monocytogenes and Salmonella enterica. Environmental samples are rarely analyzed immediately, but instead may be batched for later analysis or shipped to an off site testing facility. Multiple media on the market today is used for storage and transport of environmental samples. These various media types, differences in holding temperatures and time create variability in test sample conditions. Select time, temperature and media combinations were tested to determine their effect on Listeria monocytogenes and Salmonella enterica populations during transport and storage of samples. Cocktails of Listeria monocytogenes and Salmonella enterica were added separately to sample tubes containing D/E Neutralizing Broth, Neutralizing Buffer or Copan SRK Solution. Bacterial counts at 0, 12, 24 and 48 hours post inoculation were compared. Neutralizing Buffer and Copan SRK Solution maintained consistent bacterial populations at all temperatures. At 10Â° and 15Â°C, D/E Broth supported bacterial growth. This study helps validate the use of D/E Neutralizing Broth, Neutralizing Buffer and Copan SRK Solution for environmental sample transport and storage at proper holding temperatures. At temperatures >10Â°C Neutralizing Buffer or Copan SRK solution should be used if quantifying microbial recovery.
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