Characterization of biological contaminants in the Rio Grande from Las Cruces, New Mexico in the United States to Ciudad Juarez, Chihuahua, Mexico using a hollow-fiber ultrafiltration system

The contamination of the Rio Grande by pathogenic microorganisms is of public health concern on both sides of the U.S.-Mexico border. The aims of this dissertation were: (i) to optimize an ultrafiltration system to simultaneously concentrate and detect viruses, bacteria and protozoa; (ii) to develop a selective detection method for the human pathogen Helicobacter pylori; and (iii) to survey the Paso del Norte region surface water for the presence of bacterial indicators of pathogenic microorganisms. During ultrafiltration the addition of Tween-80 clearly increased the recovery of seeded microbes from 10 L, which was 50, 60 and 90% for viruses, protozoa and bacteria, respectively.; Helicobacter pylori was enumerated in the Rio Grande at concentrations ranging from 0 to 2.0 x 102 colony forming units per liter (CFU/L) in five of six sites analyzed. Presumptive identification by cell culture was possible in five of twenty four water samples (25%), while PCR confirmation was obtained in 12 (50%) of the twenty four water samples. Levels of heterotrophic bacteria ranged from 3.9 x 10 4 to 1.0 x 1010 CFU/L, total coliforms ranged from 2.0 x 102 to 4.3 x 107 CFU/L, and values of fecal coliforms were between 7.5 x 101 and 1.8 x 108 CFU/L. Numbers of putative Salmonella species grown on selenite cystine ranged from 8.9 x 10 2 to 1.1 x 108 CFU/L. Conventional media was supplemented with a mixture of trimethoprim, sulfamethoxazole, polymyxin B, and vancomycin and these media were compared to tetracycline and ampicillin-amended agars and minus antibiotic agars.; Percentage of total coliforms, fecal coliforms and putative Salmonella species able to grown in the presence of antibiotics of ranged from 0 to 4.5, from 3 to 40, and from 4 to 23%, respectively. There was no apparent seasonal effect observed between samples. These results indicate that both Rio Grande and Agricultural drain samples harbor fecal bacteria that include pathogens like H. pylori and coliforms which can grow in the presence of antibiotics.