The FDA has approved broader use for Cubist Pharmaceuticals’ Cubicin intravenous antibiotic to also treat bloodstream infections, including a form of endocarditis.Cubist plans to market Cubicin for the new indication immediately, the Lexington, MA-firm said.Cubicin was originally approved in late 2003, for the treatment of complicated skin and skin structure infection and has reached $100 million in sales since then.In November 2005, the company announced it would boost the size of its hospital sales force from 99 to 135 in anticipation of today’s regulatory approval.