Survival and distribution ofYersinia enterocolitica in a tropical rain forest stream

Abstract

The survival and activity ofYersinia enterocolitica andEscherichia coli in a tropical rain forest stream were studied in situ in membrane diffusion chambers. Direct counts ofY. enterocolitica decreased by one order of magnitude during the first 6 h and then remained constant. Densities ofE. coli increased over time, doubling after 2 days. Physiological activity ofE. coli dropped initially and then stabilized at 85%. Physiological activity forY. enterocolitica increased during the first 6 h, then declined to 50%. The percentage of respiring cells as measured by 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride reduction decreased forE. coli to 10%, whereasY. enterocolitica remained near 25%;Y. enterocolitica is a survivor in tropical freshwater, as isE. coli. Indirect and direct fluorescent antibody (FA) methods were evaluated for the direct detection ofY. enterocolitica in natural habitats. Natural densities of FA-positive cells were always less than 10 cells ml−1, and no isolates were obtained by culturing samples.