Dear Miriam,

I suggest you to contact with the authors of the paper in PLoS citing these strains, asking to share them with your institution.

Dear Miriam,

Here are some good resources for finding strains of E. coli:

 For clinical and shiga toxin-producing strains there is the STEC Center at Michigan State University and the E. coli Reference Center at Penn State (see links below).

The STEC Center has the ECOR15 strain you are looking for, but I haven't yet found a source for the other strain you seek.

If you are looking for a positive control for PCR, the best strain for that purpose depends on where your primer sequences came from.  If you are using the standard E. coli reference genome for primer sequences (usually this is MG1655 or W3110), then the best positive control would be the strain that your primer sequences were taken from.  Both of these strains are available at the E. coli Genetic Stock Center at Yale University, (again the link is below).

In this interest of full disclosure I should mention that I run the E. coli Genetic Stock Center.

http://shigatox.net/new/

http://vbs.psu.edu/research/centers/ecoli

http://cgsc.biology.yale.edu

Thank you so much John!

You've been extremely helpful!