MBNA Corp. announced that it has acquired the $550 million credit card portfolio of AmSouth Bancorp., for an undisclosed sum. Under terms of the agreement, MBNA will own AmSouth's credit card receivables and will manage the card program under the AmSouth brand. MBNA will also be responsible for all credit, Customer Service, Customer Assistance and operational decisions concerning the 390,000 account portfolio. Additionally, MBNA will market credit card products and services to AmSouth's existing and future customers through AmSouth's 670 bank locations and the AmSouth web site.