BOSTON -- An outbreak of an unusual form of yeast infection in an intensive care ward for newborns has been traced to the medical staff's failure to wash their hands after playing with their dogs.
The yeast, first identified in a rhinoceros in 1925, made 15 babies sick at Dartmouth-Hitchcock Medical Center in Lebanon, N.H., from 1993 to 1995. Epidemiologists from the Centers for Disease Control and Prevention were called in to investigate.
The medical detectives believe that dogs carried the yeast, known as Malassezia pachydermatis, and that the pet owners got it on their hands. When they got to the hospital, they handled babies without washing thoroughly. One and perhaps more got infected. Then nurses and doctors spread the yeast from baby to baby when they touched them.
In newborns, the yeast causes a variety of symptoms, including fever and irritability, and can be fatal. But none of the babies at Dartmouth-Hitchcock died of the infection.
Dr. William R. Jarvis, one of the CDC investigators, said the case is a clear example of why scrubbing up is so critical, especially when dealing with premature babies with underdeveloped immune defenses.
"Hand washing is probably the most effective way to interrupt the transfer of pathogens," he said.
Yet failure to wash is a major problem in hospitals, where doctors and nurses often feel rushed and find scrubbing easy to skip.
When asked about their habits, the Dartmouth-Hitchcock staff said they usually did wash their hands. In fact, two-thirds claimed they scrubbed between patients 100 percent of the time.
However, when the investigators watched them work, they found they actually washed up between patients only one-third of the time.
"It's been a problem for hundreds of years and one we keep working on," Jarvis said.
The CDC team wrote up its investigation in Thursday's issue of the New England Journal of Medicine.
An accompanying editorial by Drs. Leonard and Eugenia Marcus of Newton, Mass., recommended that medical people get their pets treated promptly if they get sick. They should also change their clothes when they get to the hospital to minimize the chance of bringing in germs.
The discovery also illustrates the continuing threat of what doctors call zoonoses -- diseases that pass from animals to people. These include such things as rabies, cat scratch fever and salmonella.
M. pachydermatis is minor player in this menagerie. It sometimes causes ear infections in dogs. However, it's rarely a problem in people.
Sick premature babies are an occasional exception. Their immune defenses are low. They are hooked to catheters that give germs an entry way into their bodies. And they receive fat-rich feeding solutions that are ideal growing mediums for yeast.
In all, the CDC found the exact same strain of the yeast was carried by the 15 babies who got sick, as well as nine other infants and one health care worker who showed no signs of infection, plus three dogs.
The last case was seen in January 1995, and the yeast has not been spotted in the hospital since.
"The outbreak was really controlled by reinforcing basic infection-control practices, of which hand washing is most important," said Dr. C. Fordham von Reyn, chief of infectious diseases at the hospital.