Enterovirus and Bacterial Evaluation of Mississippi Oysters

Abstract

The numbers of enteric viruses and fecal coliform bacteria in oysters and water samples collected along the Mississippi Gulf coast during 1979 were determined. Ten viral isolates, representing members of the poliovirus group, were identified from an approved oyster harvesting site. The number of virus isolations increased to 51 when oysters were collected from a prohibited harvesting location. The majority of isolates were identified as poliovirus type 1 or 2, coxsackievirus B3 and B4, and echovirus type 24. Fecal coliforms in water samples collected at approved and prohibited locations confirmed the classification assigned to each area by the Mississippi State Board of Health. The numbers of fecal coliforms in oyster samples collected at the identical sites did not reflect the levels observed in water samples. There was no positive correlation between indicator bacteria in the water column and the number of viruses in the shellfish examined. These results imply that viral analyses of shellfish may be needed as an adjunct to bacteriological analyses so that shellfish safety is verified. TABLE 1. Fecal coliform levels in water and oyster samples taken during 1979. Pass Christian Reef Graveline Bayou Water Water Median MPN/ 100 ml Oyster Median MPN/lOO ml Oyster Month Surface Bottom Mean MPN/lOO gr Surface Bottom Mean MPN/lOO gr

Relaying to Decrease the Concentration of Oyster-Associated Pathogens

“…Little correlation has been observed between the level of fecal coliforms and viruses in oysters (5,6,29). This study has shown that indicator bacteria and enteric pathogens are eliminated at similar rates, but in some instances, viruses were detected after the fecal coliform level had reached <50 per 100 g (study 1C, Table 2 and 5).…”

“…The filter feeding mechanism of the oyster (10,11,18) is the process by which contamination occurs. Bacteria (13,21,26,27,28), viruses (5,6,8,13,22,30), and other microorganisms as well as foodstuff (23) are ingested.…”

Indicator organisms for estuarine and marine waters

“…The coliform MPN of water and coliform MPN, E. coli MPN, and aerobic plate count of the oysters, thus, were not indicative of the presence of viruses [158]. No correlation was found between fecal coliforms in water and the number of viruses isolated from oysters collected from approved and prohibited oyster harvesting sites in coastal Mississippi [164,165]. Rather than using fecal coliforms as indicators, it was proposed that a virus, such as poliovirus type 1, could be helpful, and that concentrations of a viral or bacterial indicator in the sediment might also be valuable as a predictor of health risk from viral contamination.…”

“…Contamination of shellfish with enteric viruses has been well documented, and the subject has been reviewed extensively by several investigators [163][164][165]. Enteric viruses have been isolated from shellfish collected from approved shellfishing waters.…”

“…Fecal streptococci and enterococci, which survive longer in seawater than coliforms, but have not been studied as thoroughly as the coliforms, have been proposed as indicators for the presence of enteric viruses [71,173], but, as stated above, cannot be relied upon to indicate the presence of viruses. Viral indicators, suggested for waste-water, include Sabin vaccine poliovirus [164,[174][175][176], cyanophage [177,178], and coliphage [179,180]. The difficulties associated with the use of a virus as an indicator are many, the most important of which are: no single human virus is always present in every sewage-impacted area; viruses are often present only in relatively small numbers; and better methods for virus concentration are badly needed [175].…”