Tissue distribution of a coliphage and Escherichia coli in mussels after contamination and depuration

Abstract

Experiments were undertaken to determine the tissue distribution of Escherichia coli and a coliphage after contamination of the common mussel (Mytilus edulis). Mussels were contaminated with high levels of feces-associated E. coli and a 22-nm icosahedral coliphage over a 2-day period in a flowing-seawater facility. After contamination, individual tissues were carefully dissected and assayed for E. coli and the coliphage. Contaminated mussels were also analyzed to determine the tissue distribution of the contaminants after 24and 48-h depuration periods. The majority of each contaminant was located in the digestive tract (94 and 89% of E. coli and coliphage, respectively). Decreasing concentrations were found in the gills and labial palps, foot and muscles, mantle lobes, and hemolymph. Our results indicate that contamination above levels in water occurred only in the digestive tract. Contaminated mussels were depurated in a commercial-scale recirculating UV depuration system over a 48-h period. The percent reductions of E. coli occurred in the following order: digestive tract, hemolymph, foot and muscles, mantle lobes, and gills and labial palps. The percent reductions of the coliphage were different, occurring in the following order: hemolymph, foot and muscles, gills and labial palps, mantle lobes, and digestive tract. Our results clearly demonstrate that E. coli and the coliphage are differentially eliminated from the digestive tract. The two microorganisms are eliminated at similar rates from the remaining tissues. Our results also clearly show that the most significant coliphage retention after depuration for 48 h is in the digestive tract. Thus, conventional depuration practices are inappropriate for efficient virus elimination from mussels.

Uptake and persistence of human associatedEnterococcusin the musselMytilus edulis:relevance for faecal pollution source tracking

“…Faecal bacteria and viruses taken up by M. edulis are mainly located in the intestine and digestive gland (Power and Collins 1990; Doré and Lees 1995). Depuration for 48 h in noncontaminated seawater at temperatures above 5°C will often reduce concentrations of faecal bacteria to low or undetectable levels whereas viruses generally disappear more slowly (Doré and Lees 1995; Cusson et al.…”

“…2008). Faecal indicators taken up by M. edulis are mainly located in the intestine and digestive gland, and to a minor extend in the gills and labial palps (Power and Collins 1990; Doré and Lees 1995). After uptake, some bacteria are enzymatically degraded by M. edulis , and some are excreted again in a viable form.…”

Changes in the microbiological quality of shellfish, brought about by treatment with high hydrostatic pressure

“…are indigenous to the estuarine environment (Wekell et al, 1994), they would not normally be present in sufficient numbers to cause illness. However, molluscs filter feed and can concentrate pathogenic bacteria, particularly in the intestinal tract and gills (Power & Collins, 1990). This is of particular concern in oysters as they are often eaten raw (Wekell et al, 1994;Lo´pez-Caballero et al, 2000) and are consequently responsible for a very high proportion of the outbreaks of infectious disease associated with molluscan shellfish (Gillespie et al, 2001).…”

Evaluation of two viral extraction methods for the detection of human noroviruses in shellfish with conventional and real-time reverse transcriptase PCR

“…The extraction methods were tested on mussels being a representative for the bivalve shellfish category. Prior the extraction methods, the digestive glands which are the main concentrating organs of pathogens, were dissected reducing the amount of tissue residues (Metcalf et al 1979;Power and Collins 1990).…”