In a controlled , randomized , and double blinded clinical trial , foals with ultrasonographic evidence of pulmonary abscesses ( abscess score @-@ cm ) were randomly allocated in @ treatment groups : ( @ ) gamithromycin IM q@ days ( n = @ ) ; ( @ ) azithromycin with rifampin , PO q@h ( n = @ ) ; or ( @ ) no antimicrobial treatment ( controls ; n = @ ) .