A lack of predatory interaction between rumen ciliate protozoa and Shiga-toxin producing Escherichia coli.
OBJECTIVE
To investigate interactions between rumen protozoa and Shiga toxin-producing Escherichia coli (STEC) and to ascertain whether it is likely that rumen protozoa act as ruminant hosts for STEC.


RESULTS
The presence of stx genes in different microbial fractions recovered from cattle and sheep rumen contents and faeces was examined using PCR. In animals shedding faecal STEC, stx genes were not detected in the rumen bacterial or rumen protozoal fractions. Direct interactions between ruminal protozoa and STEC were investigated by in vitro co-incubation. Rumen protozoa did not appear to ingest STEC, a STEC lysogen or non-STEC E. coli populations when co-incubated.


CONCLUSIONS
The ruminal environment is unlikely to be a preferred habitat for STEC. Bacterial grazing by rumen protozoa appears to have little, if any, effect on STEC populations.


CONCLUSIONS
This study indicates that ruminal protozoa are unlikely to be a major factor in the survival of STEC in ruminants. They appear as neither a host that protects STEC from the ruminal environment nor a predator that might reduce STEC numbers.
Burow
L C
LC
Department of Microbiology, The University of Queensland, Brisbane, Qld, Australia.
Gobius
K S
KS
Vanselow
B A
BA
Klieve
A V
AV
D000818:Animals; D002417:Cattle; D016798:Ciliophora / Q000254:growth & development / Q000382:microbiology*; D004269:DNA, Bacterial / Q000032:analysis; D004926:Escherichia coli / Q000254:growth & development*; D016133:Polymerase Chain Reaction; D011235:Predatory Behavior; D012417:Rumen / Q000382:microbiology* / Q000469:parasitology*; D022603:Shiga Toxins / Q000096:biosynthesis* / Q000235:genetics
D004269:DNA, Bacterial; D022603:Shiga Toxins