Porcine enterotoxigenic Escherichia coli O149: Virulence and molecular tools to study its distribution

Enterotoxigenic Escherichia coli O149 (ETEC O149) is a dominant serogroup of ETEC causing porcine postweaning diarrhea (PWD) worldwide. The objectives of the study were to (a) assess the virulence of an emerged clone of ETEC O149:H10 in an experimental PWD model (b) develop an effective detection tool to identify pigs infected with ETEC O149 and (c) study the distribution and kinetics of ETEC O149 in sows, piglets, and their environment on two swine farms.;A new ETEC O149:H10 clone has been associated with increased intensity and frequency of diarrhea in piglets in Ontario, Canada. This new clone harbours a plasmid pTENT2, carrying the tetracycline resistance gene tetA and the virulence genes estA, paa, and sepA which were not present in earlier ETEC O149 clones from the same region. In the present study, the severity of diarrhea was significantly higher in piglets inoculated with a pTENT2-positive ETEC O149 compared to piglets inoculated with a pTENT2-negative ETEC O149, suggesting an important role played by this plasmid in the increased intensity of diarrhea. The use of tetracycline in feed had no effect on severity of diarrhea and on persistence of ETEC O149 in the intestine when the piglets were inoculated with pTENT2-positive ETEC O149. This suggests a minimal effect of tetracycline in PWD induced by pTENT2-positive ETEC O149.;A real-time PCR assay was developed as a diagnostic and epidemiological tool using a sequence specific for E. coli O149 present on its 0 antigen gene cluster. The assay was highly specific and sensitive for the qualitative but not quantitative detection of E. coli O149 in swine fecal samples. This tool was successfully applied to assess the E. coli O149 environmental contamination and carriage by sows, and to study the kinetics of ETEC in piglets during the preweaning period. Both sows and fomites were potential sources of ETEC for the piglets. Differences were observed in the frequency of environmental contamination and sow colonization, and kinetics of ETEC in piglets between a problem and non-problem farm. Further investigations are needed to identify the influence of these factors and of immunity on the occurrence of PWD.