I no longer purchase ground meat in any form. Not after learning of how stores (major ones and little ones) do not clean their equipment properly, to avoid contamination.
Dateline showed purchased meat in many locations across the country and then tested the ground meat. This was after several people in NY were sickened and some died from ground beef contaminated with pork. (These were Jewish patients, who did not eat pork).
Frozen patties are often generic meat, and if you watch the recalls for e. coli and the like, you'll find they are typically often included in the massive recalls of tainted meat.
The NBC show is now archived, but there is a short description of that long segment:
This is a NBC followup to the adulterated ground beef...naming stores etc:
I myself was sickened one summer (1982) from contaminated McDonalds' meat. I won't go into detail, as it is gross, but never again will I eat there. We were on vacation and my son was a year old, and really, I thought my number was up! 2wks later the news reported the northern midwest states were affected the most. So I can avoid burgers now quite easily!
There was just a news item out last week about how much contamination is present in pork today. One can never be too careful where ground meat is involved!
The grinding of meat leads to all sorts of problems, and sadly places tend to not clean the equipment often enough or thoroughly enough. Grinding your own at home is the only way to control that...and make sure you do clean up properly.
And if this isn't enough--now C. difficile in meat!?