( ( Chlamydia ( pneumoniae infection ) ) ( ( has ( been ( linked ( to ( ( ( ( atherosclerosis , ) ( heart attack ) ) and ) stroke ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Chlamydia) (NN pneumoniae) (NN infection)) (VP (VBZ has) (VP (VBN been) (VP (VBN linked) (PP (TO to) (NP (NP (NNS atherosclerosis)) (, ,) (NP (NN heart) (NN attack)) (CC and) (NP (NN stroke))))))) (. .)))
Chlamydia pneumoniae infection has been linked to atherosclerosis, heart attack and stroke.
(ROOT (S (NP (DT A) (NN heart) (NN attack) (CC or) (NN stroke)) (VP (VBZ is) (ADVP (RB often)) (NP (NP (DT a) (NN result)) (PP (IN of) (NP (JJ untreated) (NNS atherosclerosis))))) (. .)))