from any culture collection in Germany DSM or UsA ATCC.search for reference if it is registered

try the following google scholar search http://scholar.google.com/scholar?hl=en&q=coli+EC538

most if not all the listed papers reported use of the strain, so you can request any of the corresponding authors for the strain.

Dear Ahmed and Avijit

Thank you for your help.

Ahmed, I've checked and it looks like this strain is not registered. There are no strains available at ATCC with this number.

Avijit, I've already asked some authors for this strain but unfortunately got no answer for my request. But I'll keep on trying.