We don't have a washer in the MH, but it's no different than a front loader at the S&B. We used a detergent that claimed to be safe for all washers, but it wasn't specifically labeled as HE (High Efficient). After awhile, we had a bad odor in our washer. After reading an article about smells in front loader washers, we switched to a HE labeled detergent.
The HE detergents don't make as much soap suds. As a previous poster mentioned, it is the soap residue that causes the odor. The soap residue attracts bacteria. The odor was greatly reduced by switching to an HE detergent. We also clean the door seal regularly. Ours usually traps a little bit of water, even with the door open all the time, it usually doesn't completely dry.
Between the HE detergent and cleaning the door seal on a monthly or so basis, we have eliminated the odor in our Front Load washer.
-Michael