Luis Valbuena hit a two-run homer in the top of the 13th off Alfredo Simon (2-1) for a 4-2 Cubs lead.
Michael Bowden (0-1) couldn't hold it. He gave up a single by Xavier Paul, Brandon Phillips' double and Bruce's two-run double that tied it.
Izturis' single past diving shortstop Starlin Castro sent the Reds to their seventh victory in eight games on their homestand.
Long games are the norm in Cincinnati, where the Reds have gone extra innings four times and had another game suspended overnight because of rain.
The Cubs have dropped seven of eight and 12 of 15, leaving them in last place in the NL Central at 5-13.
The game matched two starters who recently went head-to-head for the fifth spot in Cincinnati's rotation. Both gave up a pair of runs and didn't figure in the decision.
Left-hander Travis Wood, who was Cincinnati's second-round draft pick in 2005, couldn't hold a 2-0 lead in the seventh. Bruce led off with his first homer of the season and Chris Heisey singled. Jack Hannahan came off the bench and hit a triple off James Russell—his fifth pinch hit of the season—to tie it.
Wood was traded to the Cubs along with two minor leaguers for reliever Sean Marshall after the 2011 season, when the Reds chose to keep right-hander Mike Leake at the back of their rotation. Leake, who was Cincinnati's top pick in the June 2009 draft, had never pitched against Wood before.
David DeJesus opened the game with a home run on Leake's third pitch, the 13th leadoff homer of his career. Castro's RBI single in the third inning made it 2-0 and gave him a 14-game hitting streak, matching the best of his career. It's the longest active streak in the majors.
Cincinnati shortstop Zack Cozart was back in the lineup after missing one game with an injured index finger. He got hit by a ball while trying to bunt on Saturday and initially thought it was broken. X-rays were negative.
Yet another Reds player got hurt Monday, though.
Reliever Jonathan Broxton left in the eighth inning after knocking down Nate Schierholtz's liner up the middle. A trainer examined Broxton's right hand, and the pitcher flexed it several times before leaving the game. X-rays were negative.
The defending NL Central champions have been hit hard by injuries. Marshall, top starter Johnny Cueto, cleanup hitter Ryan Ludwick and catcher Ryan Hanigan are on the disabled list.
Shin-Soo Choo kept getting hit—and getting on base—at a phenomenal pace. Wood hit him in the right arm with a pitch in the sixth. Choo has been hit by pitches 10 times already, a Reds record for one month.
Choo has reached base safely in 14 of his 18 plate appearances over the last three games.
NOTES: Marshall started a rehab assignment with Triple-A Louisville. He hasn't pitched this season because of shoulder tendinitis. ... Castro also hit in 14 games from the end of the 2011 season through the start of 2012. ... The Reds have fanned at least 10 batters in five straight games for the first time in modern franchise history.
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