Both of Guthrie's goals come from free-kicks - the first unintended, as it flew through a packed Birmingham penalty area, and the second an accurate set-piece that found the net via a post.
Those goals helped Reading make it 13 points from their last five league games and leave Birmingham unable to cap a memorable week with a third successive victory.
Lee Clark's men beat Sheffield Wednesday 4-1 in the league last time out and then followed that up with a 3-1 cup win over Swansea, and buoyed by those successes they started brightly.
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Manali has Friday morning's forecast for the west of the Meridian region.
Manali has Friday morning's forecast for the east of the Meridian region.
The schools attended by two teenagers killed with their parents when their seaplane crashed in Canada have paid tribute to the pair.