Using standard procedures, aerobic plate counts (APC), total and fecal coliform most probable number (MPN) determinations, and analyses for Salmonella, Arizona, Shigella and Edwardsiella tarda were performed on 335 fresh and 342 frozen sample units of channel catfish. APC values for 93.0% of the fresh and 94.5% of the frozen samples were
The behavior of microorganisms was studied in mung beans and alfalfa seeds before and after germination in modified, commercially available bean-sprouting kits. The microorganisms were enumerated by the aerobic plate count (APC) and by total yeast and mold count procedures. Salmonella species were artificially inoculated into selected samples and were enumerated by the most probable number (MPN) method. After germination of the beans or seeds into mature sprouts, significant increases were noted in APCs and in MPN values of Salmonella species. Although counts of yeasts and molds did not increase significantly after germination, these samples showed an increase in toxic Aspergillus flavus and potentially toxic Alternaria species. The presence of toxic Penicillium cyclopium molds also increased substantially in 5 samples of a single brand of mung beans. Analysis of selected sprout samples, however, showed no presence of aflatoxin.
Four methods of sample preparation were compared for their relative efficiency in recovering Salmonella from imported frog legs. No significant difference (P > 0.10) was observed in the efficiency of submersion, blending, and stomaching methods, but rinsing recovered significantly fewer (P < 0.01) Salmonella-positive frog legs than the other three methods. No significant difference (P > 0.25) was observed in the number of positive frog legs recovered by selenite cystine or tetrathionate broth. Salmonella-Shigella agar, when streaked from either of these broths, gave significantly fewer (P < 0.01) Salmonellapositive frog legs than brilliant green, bismuth sulfite, xylose lysine deoxycholate, and Hektoen-enteric agars. Use of xylose lysine deoxycholate and Hektoenenteric agars, as a supplement to the other three selective agars, resulted in detection of an additional 11 and 6 Salmonella-positive frog legs, respectively. A variety of serotypes, mostly uncommon, was recovered. One Salmonella serotype (6,14,24:r,i:e,n,z15), possessing a heretofore unreported antigenic formula, was isolated.
An assay for the enzyme glucuronidase was used to determine the presence of Escherichia coli in selected, naturally contaminated high moisture foods. Raw pork sausage, ground turkey, and ground beef were inoculated into tubes containing the substrate 4-methylumbelliferyl beta-D-glucuronide (MUG) in lauryl tryptose (LT) medium. After incubation at 35°C for 24 h, the inoculated LT-MUG tubes were examined under longwave ultraviolet light for the presence of a fluorogenic glucuronidase end product. A fluorescing tube indicated the presumptive presence of E. coli. The 10 day most probable number method of the AOAC and the LT-MUG procedure gave comparable recoveries of E. coli.
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