Saints captain Bednarek sloppily conceded possession deep inside his own half with a poor clearance, which allowed Justin Kluivert to work the ball to Christie, who expertly whipped the ball into the bottom left corner from almost 25 yards.
Creative midfielder Christie conjured a fine assist for Dango Ouattara’s 14th-minute opener before swiftly firing home a superb second to help put the Cherries on the cusp of the Champions League qualification spots.
Saints were seeking to record consecutive top-flight wins for the first time since February 2022 following a 2-1 success at fellow strugglers Ipswich before last weekend’s FA Cup exit at the hands of Championship club Burnley.
As Bournemouth continued to sit back, Sulemana collected a pass from Paul Onuachu to drill his first Premier League goal since May 2023 into the bottom right corner.
Defeat for bottom club Southampton was their 20th of a miserable top-flight campaign as near neighbours Bournemouth deservedly claimed local bragging rights and a first league double in this fixture.