Differential plating medium for quantitative detection of histamine-producing bacteria.

A histidine-containing agar medium has been devised for quantitative detection of histamine-producing bacteria that are alleged to be associated with scombroid fish poisoning outbreaks. The responsible bacteria produce a marked pH change in the agar, with attendant color change of pH indicator adjacent to the colonies, thus facilitating their recognition. Proteus morganii and Klebsiella pneumoniae were the two most common histidine-decarboxylating species isolated from scombroid fish and mahi mahi.

Aerobic Plate Counts of Frozen Blanched Vegetables Processed in the United States.

Aerobic plate counts were determined for 575 packages of frozen vegetables processed by 24 factories located in 12 states. The type of vegetable and the method of processing both influenced microbial populations; peas yielded some of the lowest counts while French style green beans gave higher figures than the cut variety. Using the 3-class sampling plan of the International Commission on Microbiological Specifications for Foods, the acceptance rate for the 115 lots would have been 74% for the m value specification of 10 per gram.

Application of replica plating and computer analysis for rapid identification of bacteria in some foods. II. Analysis of microbial flora in irradiated Dover sole (Microstomus pacificus).

This investigation was carried out to determine the nature of the microbial flora shifts in dover sole as a result of irradiation and storage at 6 C. The relationship was determined between the microorganisms which initially survive irradiation and those making up the final spoilage flora. A total of 2,723 isolates were examined by use of the replica-plating and computer analysis method.

Application of replica plating and computer analysis for rapid identification of bacteria in some foods. I. Identification scheme.

A method was devised and tested for a quantitative identification of microbial flora in foods. The colonies developing on the initial isolation plates were picked with sterile toothpicks and inoculated on a master plate in prearranged spacing and order. The growth on the master plates was then replicated on a series of solid-agar plates containing differential or selective agents.

CHEMICAL SENSITIZATION OF CLOSTRIDIUM BOTULINUM SPORES TO RADIATION IN MEAT.

Beef ground round inoculated with 1,000,000 spores of Clostridium botulinum 33-A per gram and containing various additives was exposed to gamma radiation. Spores were inactivated in samples (irradiated at 2.0, 2.