Q-230. Bacterial Pathogens in the Rio Grande Basin

K. L. Sternes, K. Little, D. Sauerzopf;
Sul Ross State Univ., Alpine, TX.

Water in the western United States is a scarce commodity and assuring the continued good quality of water for use in agriculture is a constant battle. The Rio Grande Basin watershed supplies water for three US states and four Mexican states. This research provides a four year survey of selected pathogens present in the Rio Grande from its headwaters in Colorado to its mouth in the Gulf of Mexico and provides a baseline for seasonality and distribution of these potential pathogens. During the years 2004 through 2007, over 700 samples each of water, sediment and biofilm were collected. These samples were collected 4 times a year from among 71 pre-selected sites which are divided into six regions. Samples from all years were analyzed using both chromogenic and non-chromogenic media and, beginning in 2006, DNA was extracted from all water and sediment samples for molecular studies. The following pathogens were targeted: Escherichia coli, E. coli O157, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella spp., Staphylococcus aureus and Vibrio. Significant differences were found between regions, seasons and between sampling dates for several of the target organisms. The Rio Grande from Albuquerque, NM upstream to the headwaters in Colorado had quite low numbers of bacteria. From Albuquerque, NM down to Canutillo, TX incidence of these pathogens was slightly higher but not statistically different (P=0.05). The numbers of pathogens in the Texas section of the Rio Grande was significantly higher (P=0.05), double or more of that in the lower New Mexico section. The highest numbers of pathogenic bacteria were recorded around El Paso, Laredo, Roma, and Brownsville, TX. The section of the river that falls along the Texas/Mexico border from El Paso, Texas to the Gulf of Mexico, had numerically consistently higher pathogen levels that the regions north of El Paso. The distribution of the organisms of interest are influenced by environmental factors such as wildlife, precipitation and snow melt and anthropogenic factors such as population density agriculture, industry, recreation, illegal immigration and wastewater treatment in the Rio Grande Basin.