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Washing machines can harbor multidrug-resistant pathogens

At a German children’s hospital, pathogens known as Klebsiella oxytoca were repeatedly transmitted to newborns in a neonatal intensive care unit. When researchers failed to find contamination in the incubators or among healthcare workers, they traced the source of the pathogens to the washing machine. 

The study, published by the American Society for Microbiology, revealed that pathogen transmission finally stopped when the washer was removed from the hospital. Prior to this investigation, it was not known that washing machines can harbor multidrug-resistant pathogens. 

“This is a highly unusual case for a hospital, in that it involved a household type washing machine,” said study first author Dr. Ricarda M. Schmithausen. German hospitals are required to use specialized machines that wash and disinfect clothing at high temperatures and with disinfectants.

According to Dr. Schmithausen, the research has implications for household washing machines, which have been recently designed to wash at lower temperatures for energy savings. The researchers found that resistance genes, as well as different microorganisms, can persist in domestic washers at these reduced temperatures.

“If elderly people requiring nursing care with open wounds or bladder catheters, or younger people with suppurating injuries or infections live in the household, laundry should be washed at higher temperatures, or with efficient disinfectants, to avoid transmission of dangerous pathogens,” said Dr. Martin Exner. “This is a growing challenge for hygienists, as the number of people receiving nursing care from family members is constantly increasing.”

Klebsiella oxytoca is a healthy gut bacteria inside of the intestines, but can otherwise cause serious infections. The presence of these pathogens on the newborns were detected during standard screening procedures.

The clothes that transmitted K. oxytoca from the washer to the infants were knitted caps and socks to help keep them warm in incubators, as newborns can quickly become cold, even in incubators, said Dr. Exner. However, the original source of the K. oxytoca is not clear. 

The infants were not infected by K. oxytoca but were found to be colonized, which means that the pathogens were harmlessly present. The findings suggest that changes in washing machine design are required to prevent the accumulation of residual water where microbes can grow and contaminate clothes.

The study is published in the journal Applied and Environmental Microbiology.

By Chrissy Sexton, Staff Writer

Image Credit: Shutterstock/Rozhnovskaya Tanya

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