HOUSTON (AP) - Brandon Backe got through the first inning, then led the Houston Astros to their fifth straight victory.

Backe struck out six in seven effective innings, Ty Wigginton homered and drove in three runs and the Astros beat the San Francisco Giants 3-1 on Monday night.

Jose Valverde shut out the Giants in the ninth for his 29th save after LaTroy Hawkins pitched a perfect eighth for the Astros, who've won nine of their last 11. Houston has won five in a row for the first time since May 2-7.

Houston has reached the .500 mark (59-59) for the first time since June 11.

Backe (7-11) allowed a run and four hits to win for just the third time in eight starts. He rebounded from his worst outing of the season, when he gave up 11 runs in 3 1-3 innings against the Chicago Cubs last Wednesday.

''I've got to make up a lot of ground for the start I had the last time,'' said Backe, who threw 103 pitches. ''Tonight, I stayed focused on what the plan was and executed my pitches. That's pretty much the difference from being good and being horrible.''

Backe has struggled in first innings this season, allowing 21 of his 80 earned runs. He walked two batters in the first on Monday, but gave himself a psychological boost by not allowing a run.

''It's huge,'' Backe said. ''Obviously, you start the game off and you're down by one or two runs, all of a sudden you're back's against the wall. You want to steer clear of it.''

Jonathan Sanchez (8-9) didn't allow a hit for five innings, but again got no support from San Francisco's bats. The Giants have scored one run or less during 12 of his 24 appearances this season.

Sanchez didn't speak to the media after the game.

''It was a tough loss,'' said Giants manager Bruce Bochy . ''It wasn't like they hit him hard. Anytime you throw the way he did, it's a tough one to lose.''

Humberto Quintero led off the Houston sixth with a broken-bat single just over shortstop Ivan Ochoa . Backe beat out a bunt that got past Sanchez and Kaz Matsui advanced the runners with a sacrifice bunt.

Wigginton then singled to center field to give Houston a 2-1 lead.

Backe walked Rich Aurilia with one out in the seventh, but Emmanuel Burriss hit a hard grounder back to the mound to start a double play. Backe pumped his fist as he ran back to the dugout.

''Games like this are what I need to get past the previous start,'' Backe said. ''Not only did I pitch well, I pitched well in a game I needed to.''

Hawkins set down the Giants in order in the eighth, striking out two of the three batters. Wigginton hit a solo homer to left off Billy Sadler in the Astros' eighth.

The Giants won their last two games after trailing in the ninth inning or later, but Valverde made sure that didn't happen this time.

He struck out Fred Lewis , got Bengie Molina on a groundout and fanned Aaron Rowand to end it.

The Giants took a 1-0 lead in the third after Ochoa doubled and scored on Lewis' single to left. Wigginton bobbled the ball as Ochoa rounded third and his throw home was late. Wigginton made his first start of the season in left field in place of Carlos Lee , who's out 6-to-8 weeks with a broken left little finger. Lee had surgery earlier Monday.

Wigginton caught only one fly ball on Monday night, his sixth career start in left field and first since October 2006.

''It was fine,'' he said. ''It's not like I got a whole lot of action, either.''

Sanchez retired the first eight batters he faced, then walked Backe with two outs in the Houston third. Matsui flew out to end the inning.

The Astros went down in order again in the fourth. Sanchez retired seven of the first 12 Houston hitters he faced on groundouts.

Mark Loretta and Hunter Pence flied out to start the Astros' fifth and Sanchez fanned Michael Bourn for his first strikeout.

''He threw great,'' Bochy said. ''It's hard to throw better than he did tonight. He had good command, he located very well, he had good stuff.''

Notes: Sanchez has lost his last five decisions and San Francisco has lost in his last seven starts. ... Wigginton has 12 homers this season and 21 RBIs in his last 26 games with an at-bat. ... Before the game, the Astros honored Bill Blair, a former pitcher in the Negro Leagues.