At completion of intensive phase , cultures on solid media were negative in 81.3 % of participants in the rifampin group versus 92.5 % ( P = 0.097 ) , 89.4 % ( P = 0.29 ) , and 94.7 % ( P = 0.049 ) in the rifapentine 10 , 15 , and 20 mg/kg groups .