Salmonella, Campylobacter and Enterococcus spp.: their antimicrobial resistance profiles and their spatial relationships in a synoptic study of the Upper Oconee River basin.

Rivers may serve as reservoirs for enteric organisms. Very little is known about the boundaries of microbial communities in moving bodies of water so this study was undertaken to find the limits of distribution of some bacteria, focusing on enteric organisms. The presence of Salmonella, Campylobacter, and Enterococcus spp. and the antimicrobial resistance phenotypes carried by these organisms was evaluated for the Upper Oconee River basin, a small river in the lower Piedmont of northeastern Georgia, USA. Samples were obtained from 83 sites during a 3-h period on a spring day (April 2005) in an approximately 30 x 20 km region. Campylobacter spp. was isolated at 12 sites. The Campylobacter isolates from three sites were resistant to tetracycline. Of the five short-variable region (SVR) subtypes of Campylobacter that were found, three were found at more than one site, two types were found twice, and one subtype was found three times. Enterococcus was isolated at 71 sites. E. casseliflavus was the most common species. Based on species identification and antimicrobial resistance patterns, 24 types of Enterococcus were found. Salmonella was isolated from 62 sites. Of the 19 Salmonella serovars that were isolated, serovar Muenchen accounted for about 20% of the isolates. The next three most common serovars isolated, Rubislaw, Hartford, and Give, accounted for about 44% of the river isolates. Antimicrobial resistance profiling offered limited differentiation of Salmonella isolates because only seven isolates were resistant to any antimicrobial. The sites at which Salmonella, Campylobacter, or Enterococcus were isolated did not correlate with each other or with the total coliform number or Escherichia coli count for the site. However, isolates of some of the same species and type occurred in clusters that were restricted to areas within 5 to 6 km.