Jo Ellen Cockroft/Texas Great Dane Rescue/SASPCA ,texasgreatdane.com director jo ellen cockroft Lied to us when adopting out a great dane, dog was infected with staph on her side, and had a yeast infection in her ear. we went through a home check and app so they knew we had a toddler that could pipe creek, Texas

Obviously the rescue made a mistake in trusting you with a dog.  If you had done your homework on these typical dog health issues, you would not sound so uneducated nor be so angry.
 
Heartworms can be treated in a number of ways.  They do not need a veterinaran to inject the dog with the deadly immiticide.  And if that treatment is used, the dog will still test positive in 6 months and may continue to test positive for 8 to 10 months, depending on the severity of the infestation.  Ivermectin and Doxycycline regiment can rid the dog of heartworms in about the same length of time and at a 10th the cost and much less chance of killing the dog in the process.

Yeast infections, particularly in a dogs ears, are so common, they are probably up there with human headaches.  There are quite a few across the counter remedies and a 'yeast defense' in the diet can reduce or even eliminate future occurances.  
    What you refer to as a steph infection, I believe you are referring to what is commonly called a hot spot.  There is no absolute on why a dog gets them.  And they can literally appear over night.  Adding probotics to the diet can help their immune system fight them off.  You can get it at WalMart or even give a tablespoon (twice a day for a Dane) of plain non-fat Danon Yogurt (Must be Danon as the cheap stuff does not have the essentials.)

I'm sorry they called you names, but I suspect they were provoked.  Most rescues care very much about their rescues.  They do not short cut care, just because they give the shots themselves or use homeopathic veterinarian approved methods for cures.  And we are not psychics.  We can't predict what illness might appear tomorrow or the next day anymore then you can predict if your child will get a fever or an ear ache.   You should have let them have the dog back.  They would have refunded your money in full.  They would have treated the dogs medical issues and found a more suitable home for him.