A project at seven big hospitals reduced infections after colorectal surgeries by nearly one-third. It prevented an estimated 135 infections, saving almost $4 million, the Joint Commission hospital regulating group and the American College of Surgeons announced Wednesday. The two groups directed the 2 1/2-year project. The average rate of infections linked with colorectal operations at the seven hospitals dropped from about 16% of patients during a 10-month phase when hospitals started adopting changes to almost 11% once all the changes had been made. Hospital stays for patients who got infections dropped from an average of 15 days to 13 days, which helped cut costs.