There are several studies confirming MDR TB transmission in newly detected cases that have never been treated with antituberculous drugs.
This one in Russia for example, more than half of new cases of MDR TB are among people never before treated for TB, pointing to the importance of transmission
http://www.ncbi.nlm.nih.gov/books/NBK62463/
In South Africa transission of XDR TB was confirmed by genotyping methods (spoligotyping or IS6110 RFLP )