Energy-Saving Washing Machines May Not Kill Pathogens

Energy-saving washing machines that clean at lower temperatures may not be killing harmful pathogens on clothing, according to a study published in the journal Applied and Environmental Microbiology.

Researchers investigating the source of a Klebsiella oxytoca bacteria found on newborns in the intensive care unit of a hospital in Germany traced the pathogen back to a hospital washing machine. Klebsiella oxytoca bacteria naturally occur in the nose, mouth, and intestinal tract, but can cause serious infections outside of the intestines, especially in people with compromised immune systems.

Unlike the other washing machines in the hospital, the machine used to wash knit socks and caps to keep newborns warm was a residential model with lower washing temperatures. Fortunately, none of the newborns were sickened by the bacteria.

Researchers do not know how the pathogens entered the washing machine. But they believe the bacteria were spread to the clothing after the washing process, either through residual water left on the rubber mantle of the washer or through the final rinse, which ran unheated and detergent-free water through the laundry.

The study has implications for nursing homes, hospitals, and private residences that house people with underdeveloped or compromised immune systems. The researchers advised that laundry belonging to people with open wounds, bladder catheters, or infections be washed at higher temperatures and/or with efficient disinfectants. Water temperatures in household washing machines typically reach a maximum of 140 degrees F or below for energy-saving purposes. The cooler temperatures do not kill potentially harmful pathogens as effectively as higher temperatures.

A recent study found many Americans use cold water to clean laundry.