Central Maine Medical Center in Lewiston, which had been assigned a C grade from a national hospital safety group, now has an A rating.

The Leapfrog Group, a Washington, D.C.-based nonprofit that tracks health care safety, quality and value at hospitals, made the upgrade in its latest assessment of U.S. hospitals. CMMC is now one of the highest-rated hospitals in the state.

Hospital staff said it wasn’t one thing that accounted for the improved rating, but noted there were significant decreases in central line infections, urinary tract infections, surgical site infections and post-operative infections along incision lines since they started re-educating staff about standards of care and infections over the past year or so. The hospital also had improved outcomes for treating bedsores and avoiding deaths related to treatable complications such as pneumonia or heart attacks after surgery.

Other hospitals that received A ratings were St. Mary’s Regional Medical Center in Lewiston, Maine Coast Memorial Hospital in Ellsworth, Mercy Hospital in Portland, Northern Light Inland Hospital in Waterville and SMHC Medical Center in Biddeford. Maine Medical Center in Portland scored a B.