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February 2002
Vol. 5, No. 2, p 15.
news in brief

Calming cuts away?

opening artSkin wounds from surgery or an accident are susceptible to opportunistic infections, such as Staphylococcus aureus and β-hemolytic Streptococcus. When wounds become infected by microorganisms they heal more slowly, are more likely to scar, and could even affect an individual’s overall health. According to a recent study performed by researchers from Ohio State University (Columbus), psychological stress increases the frequency of such infections.

“Stress affects basic mechanisms of protection from infection from organisms commonly found in our environment,” says Phillip T. Marucha, coauthor of the study and associate professor of periodontology at Ohio State University.

To look at this connection more closely, Marucha and his team examined how wounded mice healed while under extreme stress. The study found that stressed mice were three times as likely to develop an infection as unstressed mice, and the rate of wound healing slowed by nearly one-third (Brain Behav. Immun. 2002, in press). The mice were stressed when researchers placed them in tubes for 15 hours a day and deprived them of food and water during this period. After three days of this restraint, the mice were wounded and then restrained for another five days. The control mice were also deprived of food and water, but they could roam freely in their cages. They were wounded at the same time as the confined mice.

Researchers then exposed some of the wounded mice to a strain of Streptococcus. Two hours after the initial exposure, the researchers began sacrificing the mice and continued to do so for the next 13 days to measure bacterial levels in the wounds. After removing the wounded area from each sacrificed mouse, scientists discovered that 85% of the stressed mice had infected wounds, compared with 27% of the unstressed mice. The researchers also found the presence of opportunistic Staphylococcus bacteria (the leading cause of hospital-acquired infections in humans) in the wounds of many of the stressed mice.

The bacterial levels peaked about five days after the initial wounding. The levels in the stressed mice were about 100,000 times greater than in the control mice. The wounds on the stressed mice also took 30% longer to close.

“We already know that stress delays healing by as much as 40%,” says Marucha. “In combination with [the] increased possibility of infection and delayed wound closing, the results of this study are significant for anyone who needs surgery or has a healing wound.”

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