Jan 31 - Fitch Ratings has affirmed the credit ratings of Corrections Corp. of America (CCA) as follows: --Issuer Default Rating (IDR) at 'BB+'; --$785 million secured credit facility at 'BBB-'; --$645 million senior unsecured notes at 'BB+'. The Rating Outlook is Stable. The affirmation of CCA's ratings considers the company's intention to convert to a REIT from a C-Corp. with a Taxable REIT Subsidiary (TRS) structure, which would become effective Jan. 1, 2013 given a favorable Private Let