Seasonal Variation in the Fecal Coliform Population of Louisiana Oysters and its Relationship to Microbiological Quality

Abstract

Seasonal variation was observed in the type of bacteria which comprised the fecal coliform population of oysters. Escherichia coli was the principal fecal coliform when water temperatures were below 22°C. Conversely, Klebsiella sp. predominated during the summer months. No significant relationship was observed between levels of E. coli and enterococci and non-E. coli fecal coliforms in oysters. Fecal coliform and E. coli levels were significantly (p >0.001) related in water. Klebsiella sp. isolated from oysters demonstrated considerably less multiple antimicrobial agent resistance than clinical isolates of K. pneumoniae. Fecal coliform-positive Klebsiella species had characteristics of environmental organisms. Results of this study suggest that high levels of non-E coli fecal coliforms in oysters harvested in the summer from beds meeting the fecal coliform water standard are not indicative of sewage pollution. Furthermore, it is suggested that the safety indicator in the guideline for oyster meats should be changed form fecal coliforms to E. coli.