Anisakid Parasites, Staphylococcus aureus and Bacillus cereus in Sushi and Sashimi from Seattle Area Restaurants

Abstract

Samples of salmon, tuna, mackerel, and rockfish sushi were analyzed for parasites from 32 of the approximately 50 restaurants in the Seattle area that prepare sushi. The restaurants were sampled up to three times over a 19-month period. Some specialty grocery stores providing restaurants and consumers with sashimi were also sampled. Salmon sushi was most commonly affected with almost 10% of pieces infected with a maximum of 3 nematodes per piece. Only single infections were present in mackerel sushi with frequency of 5%; and tuna and rockfish sushi were free of nematodes. All nematodes were third-stage juveniles of the genus Atiisakis. Except for two moribund nematodes, all juveniles from sushi were dead, most likely the result of the practice of using fish that have been previously frozen. The two moribund nematodes were present in one salmon sushi sample, indicating that incompletely frozen product had been used. For the sashimi, no parasites were found in tuna; however, a live anisakid was found in one collection of rockfish sashimi. Efforts to detect anisakid nematodes with nondestructive methods were generally unsuccessful. Neither inspection per ultraviolet light nor by candling was effective for salmon sushi. Candling was also ineffective for mackerel but was useful for rockfish and appears to be appropriate for the analysis of tuna sushi. Results of analyses of rice from sushi samples from 19 of the restaurants indicated that the pH levels were at 4.6 or below, and no fecal coliforms were detected. Most of the aerobic plate counts were below log 6, with only 2 between log 6 and log 7. Bacillus cereus and Staphylococcus aureus were detected in rice from six restaurants each, but in no samples were these two organisms found together, and levels were well below those of public health importance.