With the score tied, 1-1, Bruce singled and scored from third base on a fielder's choice by Paul Janish off reliever Charlie Manning (2-2). Mark Bellhorn, who singled to forge a tie in the ninth, scored on a groundout and Joey Votto followed with a two-run single to right. Aaron Herr's RBI base hit capped the frame for the Bats (52-53).
Calvin Medlock (2-1) walked one in two hitless frames for the win. Louisville starter Elizardo Ramirez allowed five hits in 6 2/3 scoreless innings, walking three and striking out two.
The late rally erased a sparkling outing by rehabbing Yankees starter Jeff Karstens, who limited the Bats (52-53) to a pair of hits and four walks with four strikeouts in six scoreless innings.
The 24-year-old right-hander suffered a broken leg on April 28 and has combined for eight Minor League starts since then. He gave up one run on three hits in six frames to beat Charlotte on July 22 in his first Triple-A start.
Angel Chavez hit a leadoff homer in the eighth for Scranton/Wilkes-Barre (58-45).