EVALUATION OF MICROBIAL INDICATORS FOR THE DETERMINATION OF THE SANITARY QUALITY AND SAFETY OF SHELLFISH

Shellfish consumed either raw or partially cooked have been implicated in the transmission of viral gastroenteritis and hepatitis A. The eff ectiveness of bacterial indicators to signal the presence of human pat hogenic viruses has been questioned. Earlier viral assays made it impr actical to monitor shellfish for viral contaminants. There exists a ne ed for rapid and sensitive assays for human enteric viruses to ensure the sanitary quality of shellfish. Sample collections of hard-shell cl ams (Mercenaria mercenaria) were taken from approved, conditionally ap proved and prohibited shellfishing areas in Narragansett Bay, Rhode Is land between July 1989 and May 1990. Clams were assayed for poliovirus and other microbial indicators (total coliforms, fecal coliforms, Clo stridium perfringens, enterococci and male-specific bacteriophage) to evaluate their usefulness as viral indicators. Of these indicators, ba cteriophage were most consistently recovered from each of the collecti on areas, and enterococci were recovered with the least frequency. Pol ovirus was detected in clams from the conditionally approved and prohi bited area primarily during the fall and winter months. On one occasio n in the prohibited area, the coliform standards for water and shellfi sh were not exceeded, although poliovirus was detected by a hybridizat ion probe assay. A viral indicator system based on bacteriophage level s would require further development and evaluation to determine the co rrelation of specific human enteric viruses and phage. New advances in nucleic acid technology may soon enable routine monitoring of shellfi sh for enteric viruses.