WASHINGTON - One "bad apple" can spread negative behavior like a virus to bring down officemates or destroy a good team, according to a new study examining conflict in the workplace.

Negative behavior outweighs positive behavior, so a bad apple can spoil the whole barrel, but one or two good workers can't "unspoil" it, researchers at the University of Washington said in the current issue of the journal Research in Organizational Behavior.

"Companies need to move quickly to deal with such problems because the negativity of just one individual is pervasive and destructive and can spread quickly," said co-author Terence Mitchell, a professor of management and organization.

If a bad apple slips through screening in the hiring process, he or she should be placed to work alone as much as possible, the study's lead author, William Felps, said.

The study defines negative workers as those who do not do their fair share of the work, are chronically unhappy and emotionally unstable, or bully or attack others.

Felps said he was inspired to investigate workplace conflict by his wife's experience with a "bad apple" and what happened when the worker was out sick for several days.

"When he was gone my wife said the atmosphere of the office changed dramatically," Felps said. "People started helping each other, playing classical music on their radios, and going out for drinks after work. But when he returned to the office, things returned to the unpleasant way they were."

"He truly was the bad apple that spoiled the barrel," Felps said.

The researchers said they found that a single "toxic" or negative team member can be the catalyst for a group's downward spiral.

In a follow-up study, the researchers found the vast majority of the people they surveyed could identify at least one "bad apple" with whom they had worked and who had produced organizational dysfunction.

Hiring managers could head off the problem by being more thorough when screening potential employees, Felps said.

He recommends checking references and administering personality tests to weed out those who are "really low on agreeableness and emotional stability."