We developed a simple, rapid method for demonstrating bacterial flagella with Ryu staining solution that gave satisfactory results for numerous motile and nonmotile bacteria. Two major advantages of this method are that the staining solution, ready for use, is stable at ambient temperature indefinitely and that microscopic examination of bacteria in the stained drop preparations can be performed rapidly.

The test for hippurate hydrolysis is critical for separation of Campylobacterjejuni and C. coli strains. Glycine and benzoic acid are formed when hippurate is hydrolyzed by C. jejuni. The test used in most laboratories is one of several variations of the ninhydrin tube test described by Hwang and Ederer (M. Hwang and G. M. Ederer, J. Clin. Microbiol. 1:114-115, 1975) for detection of glycine. We evaluated three modifications of the Hwang and Ederer method and the gas-liquid chromatographic (GLC) method described by Kodaka et al. (H.

Compact Dry TC qualifies as a rapid method kit for determining aerobic colony counts in foods. The plates are presterilized and contain culture medium and a cold-soluble gelling agent. The medium is rehydrated by inoculating 1 mL diluted sample into the center of the self-diffusible medium and allowing the solution to diffuse by capillary action. The plates can then be incubated and the colonies counted without any additional steps. The Compact Dry TC method was validated with 5 different raw meats. The performance tests were conducted at 35° and 30°C. In all required performance studies, no apparent differences were observed between the Compact Dry TC method and the Standard Pour Plate method (AOAC Official Method 966.23) for the detection level of aerobic microorganisms. For the accuracy claim (n = 60), a correlation factor of r235 = 0.9977 (35°C) and r230 = 0.9932 (30°C) could be assigned, as stated in the application for “Performance Tested Method.SM” Quality consistency and storage robustness studies, showed no significant variations in plate count results with different production lots or plates of diverse storage age.

We studied injury of Escherichia coli O157:H7 cells in 11 food items during freeze storage and methods of isolating freeze-injured E. coli O157:H7 cells from foods. Food samples inoculated with E. coli O157:H7 were stored for 16 weeks at ؊20°C in a freezer. Noninjured and injured cells were counted by using tryptic soy agar and sorbitol MacConkey agar supplemented with cefixime and potassium tellurite. Large populations of E. coli O157:H7 cells were injured in salted cabbage, grated radish, seaweed, and tomato samples. In an experiment to detect E. coli O157:H7 in food samples artificially contaminated with freeze-injured E. coli O157:H7 cells, the organism was recovered most efficiently after the samples were incubated in modified E. coli broth without bile salts at 25°C for 2 h and then selectively enriched at 42°C for 18 h by adding bile salts and novobiocin. Our enrichment method was further evaluated by isolating E. coli O157:H7 from frozen foods inoculated with the organism prior to freezing. Two hours of resuscitation at 25°C in nonselective broth improved recovery of E. coli O157:H7 from frozen grated radishes and strawberries, demonstrating that the resuscitation step is very effective for isolating E. coli O157:H7 from frozen foods contaminated with injured E. coli O157:H7 cells.Examination of frozen foods for the presence of pathogenic bacteria has been increasing in recent years because food service operations and consumers use frozen foods and food ingredients frequently. Furthermore, food samples are often frozen as test samples for investigations of food poisoning. Selective reagents are often used for enrichment culturing of food samples, including frozen food samples, because these reagents are required for preserving small numbers of the target bacteria by suppressing the growth of other contaminating bacteria. However, it has been observed that these reagents can inhibit the growth of injured pathogens (7). Thus, a method that both resuscitates injured target bacteria and suppresses the growth of other contaminating bacteria is required to isolate pathogens from food samples that may be contaminated with injured target bacteria. Since Escherichia coli O157:H7 was recognized as a food-poisoning agent in 1982, there have been many outbreaks linked to ingestion of not only beef but also vegetables and fruits, including lettuce, cantaloupe, cabbage, alfalfa sprouts, radish sprouts, and apple juice (2,4,14,15,23,25; M. Ackers, B. Mahon, E. Leahy, T. Damrow, L. Hutwagner, T. Barrett, W. Bibb, P. Hayes, P. Griffin, and L. Slutsker, Abstr. 36th Intersci. Conf. Antimicrobial Agents Chemother., abstr. K43, 1996). Many selective enrichment broth media have been used for isolation of E. coli O157:H7 from foods (5,6,8,17). We have shown previously that an enrichment method in which modified E. coli broth supplemented with bile salts and novobiocin (mECϩn) (16) is used is better than other methods for isolating E. coli O157:H7 from beef and radish sprouts artificially contaminated with the organism (10). Ho...