Current and possible alternate indicators of fecal contamination in tropical waters: A short review

Bacteria that belong to the total and fecal coliform groups have been used for several decades as indicators of fecal pollution of waters and other systems. The prevailing idea behind this is that these two groups of bacteria cannot replicate outside the gastrointestinal tract of warm‐blooded animals. Several studies conducted by this and other laboratories have indicated that these bacteria may be naturally present in certain areas of the world. Naturally occurring fecal coliforms (the genera Escherichia and Klebsiella ) have been isolated from pristine sites and from sites where there was no apparent fecal contamination. All these results lead us to the conclusion that these groups of bacteria are not adequate indicators of fecal contamination in tropical areas of the world. Alternate indicators are being tested. This laboratory and others around the world are testing the adequacy of bacteriophages (more specifically, coliphages) for this purpose. In Puerto Rico coliphages have been detected only in areas known to be contaminated with domestic sewage, but not in pristine areas, although high levels of fecal coliforms can be detected at the latter sites. All these results suggest that coliphages may be used as indicators that more realistically demonstrate fecal contamination of waters in tropical areas of the world. In addition, newer techniques, although still in the trial stages, can be used to directly detect pathogens in the environment. Of all the techniques currently available, the polymerase chain reaction is the most promising for the direct detection of pathogens and therefore for the unequivocal evaluation of the biological quality of waters.