Treating every patient who enters an intensive care unit with special disinfectant soaps and ointments greatly reduces the spread of MRSA, or methicillin-resistant Staphylococcus aureus, and cuts the rate of bloodstream infections in hospitals, a study shows. Currently, patients admitted to the I.C.U. are screened for MRSA, and those found to harbor it are placed in isolation. But a study published Wednesday in The New England Journal of Medicine found that using disinfectant soaps and ointments on every I.C.U. patient reduced bloodstream infections by up to 44 percent.