Raw milk samples collected from bulk tank trucks of milk suppliers in Wisconsin, Michigan, and Illinois were analyzed for Salmonella, Campylobacter jejuni, and Yersinia enterocolitica. Salmonella spp. were isolated from 32 (4.7%) of 678 samples, and C. jejuni was found in one (0.4%) of 237 samples. Although Y. enterocolitica was recovered from 114 (48.1%) of 237 samples, all isolates were environmental, non-virulent strains.
An international comparative study, undertaken by six laboratories to assess the performance of four selective media commonly used for the enumeration of Staphylococcus aureus in foods, revealed that Baird-Parker agar performed most satisfactorily. There was no significant difference among milk salt, tellurite polymyxin egg yolk, and kalium rhodanid - actidione - natriumazid - eigelb - pyruvat (KRANEP) agars. The type of food examined appeared to influence the performance of the media, but no specific patterns could be determined. Cultures yielding 3+ and 4+ coagulase reactions are most likely to possess thermostable nuclease activity, and are therefore most likely to be S. aureus.
The microbiological quality of 10 spices or herbs was determined by a national survey at the retail level. Aerobic plate count values for the 10 products ranged from <100 to 3.1 x 108 per g; mean values of the individual spices or herbs ranged from 1,400 to 820,000 per g. Coliform counts ranged from <3 to 1.1 x 106 per g; however, mean values were <20 per g for all products. Escherichia coli counts ranged from <3 to 2,300 per g. Except for celery seed, which had a mean value of 7 per g, all mean values were <3 per g. Yeast and mold counts were made for 5 of the 10 products. Mean values were generally low; the highest mean (290 per g) was obtained for cinnamon.
A comparison was made of enrichment broths for recovery of Campylobacterjejuni from food by the methods of Doyle and Roman (Appi. Environ. Microbiol. 43:1343-1353) and of Park et al. (Can. J. Microbiol. 27:841-842). No significant differences were found between the results obtained with the two broths. Recovery was greater, however, with a constant gas flow into the broths than with an evacuation-replacement method.
A collaborative study was conducted in 14 laboratories to evaluate the performance of the hydrophobic grid membrane filter method against the official final action method, 46.016, for enumeration of colif orms in foods. Twelve artificially contaminated samples of nonfat dry milk and canned custard were analyzed by each laboratory. The random errors (Sr2) associated with the hydrophobic grid membrane filter method were significantly lower than those of the official method, and the counts obtained by the new method fell within the 95% confidence interval of the reference method. The colif orm counts obtained by tiie hydrophobic grid membrane filter method did not differ significantly from those obtained by the reference method as measured by a 3-way analysis of variance. The new method has been adopted official first action.
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