Hundreds of thousands of patients each year suffer from infections after surgery, and experts say more than half of those infections stem from bacteria the patients themselves are carrying in their nose or on their skin. Otherwise harmless bacteria can enter the body through surgical incisions and cause infections that can require expensive treatment, slow recovery or even cause death.

But two new studies suggest relatively simple ways hospitals can prevent many infections by killing the bacteria on the patient before surgery, with methods of screening, scrubbing or pretreating the patient that many hospitals do not typically use.

“This is going to be a huge help to the infection-control crowd,” said Marcia Patrick, a nurse and board member of the Association for Professionals in Infection Control and Epidemiology, who was not involved with either study. “How can we not do this? It would truly be penny-wise and pound-foolish. And it’s the right thing to do for patients.”

The studies, published Thursday in The New England Journal of Medicine, examined infections that develop at the site of surgery, often around the incision, and afflict more than 300,000 patients a year in the United States.

While experts are increasingly trying to stop hospital-acquired infections by approaches including stepped-up hand-washing by doctors and nurses, the new studies looked at the bacteria patients may be carrying before entering the hospital, especially a common bacteria, staphylococcus aureus.

“About one-third of people at any one time carry this bacterium in their nose or on their skin,” said a co-author of one study, Dr. Henri Verbrugh, a professor of medical microbiology at Erasmus University Medical Center in the Netherlands. “It does not give them any problem, but if they go to a hospital and the skin is somehow breached, they are really prone to invasion or infection by their own bacteria.”

Dr. Verbrugh and colleagues tested patients for the bacteria using nasal swabs. They treated about 500 who carried the bacteria for five days with an antibiotic ointment on their noses and showers with soap treated with chlorhexidine, an antiseptic. After surgery, which sometimes occurred during the five-day treatment, those patients were 60 percent less likely to develop infections than patients receiving a placebo of ointment and soap.

The study included only patients whose operations were extensive enough to require at least five days of hospitalization. Dr. Richard P. Wenzel, an infectious disease specialist at Virginia Commonwealth University, who wrote an editorial about the studies, said he would recommend the approach primarily for serious operations like heart surgery or joint replacements, or patients with immune system problems.

But Dr. Wenzel said the method used in the second study should be adopted across the board. That study, conducted at six United States hospitals, compared the skin disinfectant hospitals use 75 percent of the time before surgery with another one. The researchers found that patients receiving the standard disinfectant, povidone-iodine, were significantly more likely to develop infections. Those cleaned with the alternative, chlorhexidine-alcohol, got 40 percent fewer total infections, and half as many staphylococcus aureus infections.

A study author, Dr. Rabih O. Darouiche, a professor of medicine at the Michael E. DeBakey Veterans Affairs Medical Center in Houston, said chlorhexidine-alcohol was recommended a decade ago by the Centers for Disease Control and Prevention for cleaning when catheters were inserted, but had not been extensively studied for surgical preparation.

Ms. Patrick said most hospitals still used the iodine solution largely because “we’ve always done it this way.”

Cost is a factor with both studies’ methods. Dr. Darouiche said chlorhexidine-alcohol costs about $12 per patient compared with $3.50 for povidone-iodine. His study was financed by CareFusion, which makes both products. It had no access to the data.

Dr. Verbrugh, whose study was financed by several companies, said the most expensive part of his approach was the rapid-screening test for bacteria, about $20. He said some United States cardiac departments had begun using the nasal ointment for all heart surgery patients, without screening them for bacteria.

Experts not involved in the studies said the added costs of the methods were dwarfed by the money saved preventing infections, which can run to tens of thousands of dollars per patient.

“Everybody wins on this,” Dr. Wenzel said. “Patients obviously have less morbidity, and hospitals and medical centers and insurers save a lot of money.”