Relationship of human-associated microbial source tracking markers with Enterococci in Gulf of Mexico waters.

Human and ecosystem health can be damaged by fecal contamination of recreational waters. Microbial source tracking (MST) can be used to specifically detect domestic sewage containing human waste, thereby informing both risk assessment and remediation strategies. Previously, an inter-laboratory collaboration developed standardized PCR methods for a bacterial, an archaeal, and a viral indicator of human sewage. Here we present results for two subsequent years of field testing in fresh and salt water by five laboratories across the U.S. Gulf Coast (two in Florida and one each in Mississippi, Louisiana and Texas) using common standard operating procedures (SOPs) developed previously. Culturable enterococci were enumerated by membrane filtration, and PCR was used to detect three MST markers targeting domestic sewage: human-associated Bacteroides (HF183), Methanobrevibacter smithii and human polyomaviruses BK and JC (HPyVs). Detection of sewage markers in surface waters was significantly associated with higher enterococci levels and with exceedance of the recreational water quality standard in four or three regions, respectively. Sewage markers were frequently co-detected in single samples, e.g., M. smithii and HF183 were co-detected in 81% of Louisiana samples, and HPyVs and M. smithii were co-detected in over 40% of southwest Florida and Mississippi samples. This study demonstrates the robustness and inter-laboratory transferability of these three markers for the detection of pollution from domestic sewage in the waters impacting the Gulf of Mexico over a coastal range of over 1000 miles.

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

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 .

Evaluation of Methods for Extraction of Enteric Virus from Louisiana Oysters.

Six techniques were evaluated for recovery of poliovirus from Louisiana oysters. The methods were compared for percent recovery rates, toxicity, ease of extraction, bacterial contamination, and final volume of oyster concentrate. Oyster samples were contaminated with 30-40 plaque forming units of Poliovirus type 1 and processed by six variations of adsorption-elution-precipitation and elution-precipitation methods. The method developed by Ellender et al. (Natural enterovirus and fecal coliform contamination of gulf coast oysters. J. Food Prot. 43:105-110) was judged to be the preferred method for gulf coast oysters.

Detection of Enteroviruses and Bacterial Indicators and Pathogens in Louisiana Oysters and Their Overlying Waters.

Field studies were conducted for 1 year to determine levels of enteroviruses in Louisiana Gulf Coast oysters and their overlying waters. Levels of human enteric viruses were compared with bacterial pathogens ( Salmonella and Vibrio parahaemolyticus ), fecal coliform levels, and physicochemical water parameters (pH, salinity, temperature, and conductivity). Samples of 20-30 oysters and 380 L of overlying water were collected monthly from both "open" and "closed" oyster growing areas. Enteric viruses were found predominantly in January and February. Viruses were isolated only from areas which exceeded the 14 fecal coliforms/100 ml standard for shellfish harvesting waters.