Plutko, a junior right-hander pitching in what is likely his game for the Bruins, tamed the Bulldogs on four hits, walking one and striking out two en route to the victory.
David Berg tossed the final 1 2/3 innings for the save, an NCAA-record 24th of the season, as the Bruins remained undefeated in the College World Series and moved within one victory of their first NCAA baseball title.
Pat Valaika supplied a first-inning RBI single and the Bruins added two unearned runs in the fourth on Eric Filia's hit.
Mississippi State starter Trevor Fitts was tagged with the loss after yielding one run over just 1 1/3 innings.
C.T. Bradford drove in the Bulldogs' only run.