It seems “energy saver” washing machines may not be killing all the potentially harmful pathogens on your clothing — as was reportedly the case at a hospital in Germany.
Researchers, in a study published last week in the journal Applied and Environmental Microbiology, detailed a case of the superbug Klebsiella oxytoca in a German hospital's neonatal intensive care unit. Routine screenings “revealed the presence of the pathogens on infants in the ICU,” according to a press release outlining the findings.
Klebsiella oxytoca bacteria are naturally occurring in the mouth, nose and intestinal tract, and are considered “healthy gut bacteria." But outside of the intestines, these pathogens can cause “serious infections,” per Healthline.
Researchers eventually traced the source of the bacteria to a washing machine in the hospital. They determined the washer transmitted the pathogens to the knitted caps and socks that were used to keep the babies warm. (Most were in the ICU because they were premature, or for an infection unrelated to the bacteria.)
Thankfully, none of the newborns were sickened, potentially because the pathogens “[had] not yet invaded tissues where they can cause disease, or because the immune system [was] effectively repelling them,” they wrote.
The transmission of the pathogens onto other surfaces, such as the knitwear, was "stopped only when the washing machine was removed from the hospital," they said.
“This is a highly unusual case for a hospital, in that it involved a household-type washing machine," said first author Ricarda Schmithausen, a hygienist with the University of Bonn in Germany, in a statement. Most of the time, Schmithausen noted, hospitals use special washing machines that wash at high temperatures. Disinfectants are typically used as well. It's not clear why the hospital at the center of the case used a household washer, but Science Alert reports it was only used for mothers' clothing and the knitwear. It was also located outside the hospital's primary laundry room.
How exactly the pathogens got into the washing machine in the first place remains unknown. But the researchers hypothesized that the pathogens "were disseminated to the clothing after the washing process, via residual water on the rubber mantle [of the washer] and/or via the final rinsing process, which ran unheated and detergent-free water through the detergent compartment."
The research “has implications for household use of washers,” Schmithausen said, noting 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.
“Resistance genes, as well as different microorganisms, can persist in domestic washing machines at those reduced temperatures,” the researchers said, noting their findings imply that "changes in washing machine design and processing are required to prevent the accumulation of residual water where microbial growth can occur and contaminate clothes."
While lower-temperature washes are safe in most instances, the case serves as a reminder that high-temperatures may be safer for those with underdeveloped or compromised immune systems.
"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, the director of the Institute for Hygiene and Public Health at the University of Bonn, in a statement.
"This is a growing challenge for hygienists, as the number of people receiving nursing care from family members is constantly increasing," Exner added.