Updated from 11:30 a.m. EDTMoody's Investors Service downgraded American Express' ( AXP) debt ratings following the card company's first-quarter earnings report, which beat estimates, but showed that credit quality is getting worse. Moody's on Friday lowered its rating on the financial institution's senior long-term debt by one notch to A2 from A3. The short-term rating was lowered to Prime-2 from Prime-1. The agency reiterated its negative outlook for the company. The ratings service also downgraded the long-term senior debt and deposit ratings of American Express Travel Related Services and its rated operating subsidiaries, including American Express Credit Corp., to A2 from A1. Moody's cut its rating on American Express bank subsidiaries to C-minus from B-minus.