import re

string = ("1John Radcliffe Hospital/Oxford/United Kingdom, 11Ruhr-Universität \n"
          "3/Bochum/Bochum/Germany, 3University of British Columbia/Vancouver/Canada, 4National \n"
          "Institute of Neuroscience, National Center of Neurology and Psychiatry/Tokyo/Japan, \n"
          "5University of Catania/Catania/Italy, 6F. Hoffmann-La Roche Ltd/Basel/Switzerland, 7 \n"
          "University of Colorado School of Medicine/Aurora/United States of America")

result = re.sub(r'(?:^|, )\d+(?!/)', r'\g<0>=', string, 0, re.MULTILINE).strip()
print(result)