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Seasonal effects on accumulation of microbial indicator organisms by Mercenaria mercenaria
W Burkhardt1, W D Watkins, S R Rippey
1Department of Microbiology, University of Rhode Island, Kingston 02881.
Abstract:
The ability of hard-shelled clams (Mercenaria mercenaria) to accumulate fecal coliforms and other microorganisms (Escherichia coli, Clostridium perfringens, and male-specific bacteriophages) was determined over a 1-year period. Twenty separate trails were conducted during different seasons to encompass a wide range of water temperatures. The greatest accumulation of microorganisms in hard-shelled clams occurred during certain periods in the spring, at temperatures ranging from 11.5 to 21.5 degrees C. These periods of hyperaccumulation did not always coincide for all organisms; the accumulation of bacteriophages was not predicted by the accumulation of either fecal coliforms or C. perfringens. Bacteriophages and C. perfringens showed significantly higher rates of accumulation than either the fecal coliform group or E. coli, especially during the spring. The higher incidence of human viral gastroenteritis associated with the consumption of shellfish during this period may be a result of the extraordinary concentration of certain microorganisms, including enteric viral pathogens.
Insights
Hard-shelled clams accumulate more fecal coliforms and other microbes in spring. This microbial accumulation, particularly bacteriophages and Clostridium perfringens, may increase shellfish-related gastroenteritis risks.
Area of Science:
- Marine microbiology
- Food safety
- Environmental health
Background:
- Shellfish can accumulate microorganisms from their environment.
- Understanding seasonal variations in microbial accumulation is crucial for public health.
Purpose of the Study:
- To determine the seasonal accumulation of fecal coliforms, Escherichia coli, Clostridium perfringens, and male-specific bacteriophages in hard-shelled clams (Mercenaria mercenaria).
- To investigate the influence of water temperature on microbial accumulation in clams.
- To assess potential links between microbial accumulation in clams and shellfish-related gastroenteritis.
Main Methods:
- Conducted 20 separate trials over a 1-year period.
- Monitored microbial accumulation in clams across a range of water temperatures.
- Analyzed accumulation rates for fecal coliforms, E. coli, C. perfringens, and bacteriophages.
Main Results:
- Greatest microbial accumulation occurred in spring, with water temperatures between 11.5 and 21.5 degrees C.
- Hyperaccumulation periods varied among different microorganisms.
- Bacteriophages and C. perfringens showed significantly higher accumulation rates than fecal coliforms or E. coli, especially in spring.
- Bacteriophage accumulation was not predictable by fecal coliform or C. perfringens accumulation.
Conclusions:
- Spring microbial accumulation in hard-shelled clams, particularly bacteriophages and C. perfringens, may be linked to increased risks of viral gastroenteritis from shellfish consumption.
- Seasonal monitoring of microbial loads in shellfish is essential for effective public health management.
- Further research is needed to understand the specific mechanisms and implications of differential microbial accumulation in shellfish.
