A comparison of the levels of faecal indicator bacteria in water and human faeces in a rural area of a tropical developing country (Sierra Leone)

Abstract

The levels of faecal coliforms (FC), indole-positive FC (presumptive Escherichia coli), faecal streptococci (FS), Streptococcus faecalis and Clostridium perfringens in the natural water sources used by 29 rural settlements in Sierra Leone were investigated. Levels of the same indicators in human faeces were also investigated. The incidence of Salmonella spp. in both habitats and the temperature, pH and conductivity of water sources were also recorded. All water sources were contaminated with the indicator bacteria, mean numbers of which occurred in the relationship FC > presumptive E. coli ≏ FS ≏ C. perfringens > S. faecalis. FC were also predominant in human faeces, the relationship of means being FC ≏ presumptive E. coli > FS > S. faecalis > C. perfringens. The need for confirmation of FC counts obtained from water sources was indicated by the large number of positive tubes produced in the FC multiple-tube dilution test from some samples which could not be confirmed as presumptive E. coli. Salmonella spp. were isolated from 13 water sources and 6% of faecal samples. Mean water temperature was high (26·2 °C), pH low (5·04) and conductivity low (34μS cm−1). Presumptive E. coli was considered the most appropriate indicator of faecal pollution of the types of water investigated. © 1982, Cambridge University Press. All rights reserved.