The bacteria contained in processed fresh edible sea urchin (uni in Japanese) were identified with high accuracy using 16S ribosornal DNA (rDNA) sequence analysis. The 586 isolates that were recovered from ten domestic products comprised 13 genera and 18 species. The food poisoning-related bacteria Bacillus cereus (B. cereus), Bacillus weihenstephanensis (B. weihenstephanensis), and Staphylococcus aureus (S. aureus) were detected in 4/10 samples, while the causative agents of bacterial opportunistic infections, Staphylococcus equorum (S. equorum), Stenotrophomonas maltophilia (S. maltophilia), Burkholderia cepacia (B. cepacia), and Serratia proteamaculans (S. proteamaculans), were detected in all 10 samples. It is not known whether these pathogens were components of the sea urchin microflora or were the result of contamination from the environment or human contact during the manufacturing process. Nevertheless, strict quality control standards are needed for the processing of fresh edible sea urchin. This is the first comprehensive analysis of the bacterial microflora of processed fresh edible sea urchin.

Yeasts of 17 processed fresh edible raw sea urchins obtained from seven countries were analyzed. In total, 45 to 7 10 4 colony-forming units CFU /g of sea urchins were recovered, and 23 yeast species were identified. Of these species, six pathogenic yeasts Candida albicans, C. sake, Debaryomyces hansenii, Pichia anomala, Rhodotorula mucilaginosa, and Trichosporon mucoides were detected from 11 sea urchins 65% . As these yeasts are opportunistic pathogens, infections in healthy individuals normally will not occur, but it should be understood that processed fresh edible sea urchin includes such opportunistic yeast pathogens.

Since no definitive standard exists for setting the expiration date of edible raw sea urchins, it is up to the importer or domestic processing manufacturer to assign an expiration date. In the present study, we performed a microbiological examination of 126 raw sea urchin samples collected from distributors at Tsukiji Market (Tokyo Metropolitan Central Wholesale Market) and evaluated their expiration dates. The expiration dates were set at 5 to 8 days after processing in approximately 80% of the products; however, microbiological examination of the samples indicated that the dates were not sufficiently accurate. Of the products, 27% did not meet the microbiological standards for freshness established by the Tokyo metropolitan government during the period preceding their expiration dates. Our results suggest that the expiration date of edible fresh raw sea urchins should be based on a microbiological examination.