Showing papers by "Michael E. Stiles published in 1973"
TL;DR: Sublethal heat treatment of two strains of Escherichia coli caused injury of the cells to be expressed, when they were plated on violet red bile agar compared to nutrient agar, and resuscitation for growth on the nonselective control medium (nutrient agar) also occurred.
Abstract: Sublethal heat treatment of two strains of Escherichia coli caused injury of the cells to be expressed, when they were plated on violet red bile agar compared to nutrient agar. Subsequent incubation in tryptic soy broth at either 20 or 37°C supported the resuscitation of the cells from injury, before the end of the lag phase. However, at a typical refrigeration temperature (4.4°C) resuscitation did not occur. In addition to resuscitation for growth on violet red bile agar, resuscitation for growth on the nonselective control medium (nutrient agar) also occurred.
15 citations
TL;DR: It is concluded that caution should be exercised in the interpretation of coliform estimates from samples which might contain stressed cells, and BDG (Buffered desoxycholate glucose) broth gave the best results for the estimation of the injured cells, however more trials on a wider range ofcoliform bacteria would be required.
Abstract: Many solid and liquid media are available for the isolation and identification of coliform bacteria. Since standards exist for coliform bacteria in some food products, reliable methods for enumerating these organisms, especially after exposure to conditions causing injury, are necessary. Solid media, such as violet red bile agar, desoxycholate agar, desoxycholate lactose agar and MacConkey agar all caused a marked underestimation of the viable counts of heat injured E. coli. Eosin methylene blue agar was eliminated from this work as a medium for enumerating coliform bacteria because its dark colour made counting of the colonies difficult. The liquid media also underestimated the viable counts of heat injured E. coli. BDG (Buffered desoxycholate glucose) broth gave the best results for the estimation of the injured cells, however more trials on a wider range of coliform bacteria would be required before this medium could be recommended for the estimation of coliform densities. Generally, it may be concluded that caution should be exercised in the interpretation of coliform estimates from samples which might contain stressed cells.
6 citations
TL;DR: Results of this study indicate that in the nonselective cooked meat medium resuscitation can be achieved in 5-6 hours, before growth of salmonellae or other contaminating microorganisms has occurred.
Abstract: Selective media are normally used for the enumeration or the enrichment of salmonellae in foods. The advantages of enriching injured salmonellae in nonselective media is known. Results of this study indicate that in the nonselective cooked meat medium resuscitation can be achieved in 5-6 hours, before growth of salmonellae or other contaminating microorganisms has occurred. Thereafter, the salmonellae could be transferred to a selective enrichment medium. However, the reliability of the dehydrated selective enrichment media appeared to be further complicated by brand and lot differences.
3 citations