Survival and detection of Bacteroides spp., prospective indicator bacteria

Preliminary experiments were performed to assess the use of intestinal Bacteroides spp. as indicators of fecal contamination of water. Viable counts of Bacteroides fragilis, an anaerobic bacterium, declined more rapidly than those of Escherichia coli and Streptococcus faecalis. However, a fluorescent antiserum prepared against B. fragilis successfully detected high proportions (18 to greater than 50%) of B. fragilis cells suspended for 8 days in aerobic water in dialysis bags at the ambient temperature. These percentages were higher than the percent viable recoveries of the two indicator bacteria used for comparison. Thus, the fluorescent antiserum test for B. fragilis might serve as a useful indicator of fecal contamination of water. An advantage of this approach over coliform analysis is the rapidity at which the test can be performed.