Aug 27 (Reuters) - The U.S. Food and Drug Administration on Monday approved Tetraphase Pharmaceuticals Inc's antibiotic for complicated intra-abdominal infections, providing a new option to combat the growing problem of treatment-resistant bacteria.

The approval allows use of the drug, Xerava, in patients aged 18 and older.

The company said it expects to launch the drug in the United States in the fourth quarter. (Reporting by Saumya Sibi Joseph and Tamara Mathias in Bengaluru; Editing by Sriraj Kalluvila)