Survival characteristics of diarrheagenic E scherichia coli pathotypes and H elicobacter pylori during passage through the free‐living ciliate, T etrahymena sp.

Free‐living protozoa have been implicated in the survival and transport of pathogens in the environment, but the relationship between non‐Shiga toxin‐producing E scherichia coli or H elicobacter pylori and ciliates has not been characterized. Six diarrheagenic pathotypes of E . coli and an isolate of H . pylori were evaluated for their susceptibility to digestion by T etrahymena , an aquatic ciliate. T etrahymena strain MB 125 was fed E . coli or H . pylori , and the ciliate's egested products examined for viable bacterial pathogens by the B ac L ight ™ LIVE / DEAD ™ assay, a cell elongation method, and by colony counts. All six diarrheagenic E . coli pathotypes survived digestion, whereas H . pylori was digested. Growth of E . coli on agar plates indicated that the bacteria were able to replicate after passage through the ciliate. Transmission electron micrographs of E . coli cells as intact rods vs. degraded H . pylori cells corroborated these results. Scanning electron microscopy revealed a net‐like matrix around intact E . coli cells in fecal pellets. These results suggest a possible role for T etrahymena and its egested fecal pellets in the dissemination of diarrheagenic E . coli in the environment. This bacterial–protozoan interaction may increase opportunities for transmission of diarrheagenic E . coli to mammalian hosts including humans.