The survival patterns of selected faecal bacteria in tropical fresh waters

The survival of various faecal bacteria used as indicators of the faecal contamination of water supplies has been investigated in a tropical environment (Sierra Leone). Isolates representing the thermotolerant coliform (TtC) and faecal streptococcus (FS) groups, Clostridium perfringens and Salmonella spp. were studied over a 48 h period of immersion in water from three different sources. Survival patterns varied according to source type, but some general observations were made: a portion of the TtC group was apparently capable of substantial regrowth; FS organisms died off at a faster rate than TtC organisms initially, but survived longer; vegetative cells of C. perfringens died off rapidly; and Salmonella spp. could survive for as long as the other faecal organisms tested. The implications of results for the analysis of tropical waters for faecal contamination are discussed.