Discriminant analysis of ribotype profiles of Escherichia coli for differentiating human and nonhuman sources of fecal pollution

Estuarine waters receive fecal pollution from a variety of sources, includi ng humans and wildlife. Escherichia coil is a ubiquitous bacterium in the i ntestines of warm-blooded animals and is used as an indicator of fecal poll ution. However, its presence does not specifically differentiate sources of pollution. A total of 238 E. coli isolates from human sources (HS) and non human sources (NHS) were collected from the Apalachicola National Estuarine Research Reserve, from associated sewage treatment plants, and directly fr om animals and tested for ribotype (RT) profile. HS and NHS isolates shelve d 41 and 61 RT profiles, respectively. At a similarity index of ca. 50%, HS and NHS isolates demonstrated four clusters, with the majority of HS and N HS isolates located in clusters C and D; isolates obtained directly from hu man and animal feces also could be grouped within these clusters. Discrimin ant analysis (DA) of RT profiles showed that 97% of the NHS isolates and 10 0% of the animal fecal isolates were correctly classified. The average rate of correct classification for HS and NHS isolates was 82%. We conclude tha t DA of RT profiles may be a useful method for identifying HS and NHS fecal pollution and may potentially facilitate management practices.