Faculty Editor: Professor Jeffrey DaCosta

A strange discovery was made in the neonatal intensive care unit of a German children’s hospital between April 2012 and May 2013, as presented in a recent article published by the American Society for Microbiology (Schmithausen, et al., 2019). Standard screening procedures revealed that an extended spectrum beta-lactamase (ESBL) producing Klebsiella oxytoca bacteria was repeatedly transmitted and colonized on the skin of thirteen premature newborn babies and one child (Schmithausen, et al., 2019). Colonization means that “pathogens are harmlessly present,” but the bacteria posed a hazard nonetheless (American Society for Microbiology, 2019). ESBLs are enzymes that render bacteria resistant to most antibiotics (Munoz-Price, 2019). K. oxytoca is a multi-drug resistant pathogen notoriously involved in several hospital-acquired infections (LaMotte, 2019).

Potential sources of the bacteria were examined, and transmission via contaminated incubators or healthcare workers was eliminated (LaMotte, 2019). Alarmingly, knitted hats and socks used to provide warmth to newborns were identified as the mode of bacterial transmission (Schmithausen, et al., 2019). Further investigation exposed the pathogen’s ultimate source: a domestic washing machine. A K. oxytoca strain was found on the washing machine’s detergent drawer and rubber drawer seal, as well as two nearby sinks in the ward, all of which were used to wash newborn laundry (Schmithausen, et al., 2019). Laboratory tests showed that this type-00531 ESBL-producing K. oxytoca strain matched the strain detected on the newborns’ skin and clothing (Schmithausen, et al., 2019). Given these findings, the machine’s use was promptly discontinued, and no further K. oxytoca colonizations were detected (Schmithausen, et al., 2019).

Dr. Ricardo Schmithausen, the article’s first author, remarked, “This is a highly unusual case for a hospital, in that it involved a household type washing machine” (American Society for Microbiology, 2019). This study emphasizes the importance of industrial washing machines in hospital settings, as their higher heat capacity achieves appropriate sanitation. However, it also has serious implications for energy-saving, domestic washing machines in our own homes. The authors advocate for “changes in washing machine design and processing to prevent accumulation of residual water where microbial growth can occur and contaminate clothes” (Schmithausen, et al., 2019). Hot water for washing and high temperature drying settings are crucial for killing germs with both domestic and industrial machines (LaMotte, 2019). According to the U.S. Department of Energy, “The warm or cold water setting will generally do a good job of cleaning your clothes. Switching your temperature setting from hot to warm can cut a load’s energy use in half” (LaMotte, 2019). Swelling environmental concerns and energy-efficiency goals favor warm or cold water washing. However, proper sanitation can potentially be sacrificed for efficiency (LaMotte, 2019). For certain types of laundry, such as hospital laundry or towels, expending more hot water and energy for a deeper initial clean can spare the relatively heftier resources required to treat a person sick from lingering contaminants.

As frequent users of domestic washing machines, we can take tangible steps to lessen their roles as “vectors of transmission” (Schmithausen, et al., 2019). Towels, for example, should be washed with hot water and dried with high heat. If not, you could “get more E. coli on your face when you dry it with a towel than if you stuck your head in a toilet and flushed” (LaMotte, 2019). Such washing and drying tactics should be embraced especially when someone is sick, and washing machines should be cleaned after particularly germy loads by running one wash cycle with bleach (LaMotte, 2019).

Thankfully, the newborns in this study were merely colonized, not infected, by the K. oxytoca bacteria and were not ill from the prolonged exposure (Schmithausen, et al., 2019). Their case illuminates potential dangers of energy-saving, domestic washing machines and promotes better laundry practices for hospitals and households alike.


  1. American Society for Microbiology. (2019, September 27). Your energy-efficient washing machine could be harboring pathogens: Lower temperatures used in ‘energy saver’ washing machines may not be killing all pathogens. ScienceDaily. Retrieved from www.sciencedaily.com/releases/2019/09/190927135202.htm.
  2. LaMotte, S. (2019, September 28). Bacteria are likely hiding in your household washing machine. Retrieved from https://www.cnn.com/2019/09/27/health/washing-machine-bacteria-wellness/index.html.
  3. Munoz-Price, S. (2019, October 15). Extended-spectrum beta-lactamases. Retrieved from https://www.uptodate.com/contents/extended-spectrum-beta-lactamases.
  4. Schmithausen, R. M., Sib, E., Exner, M., Hack, S., Rösing, C., Ciorba, P., … Exner, D. (2019, September 27). The washing machine as a reservoir for transmission of extended spectrum beta-lactamase (CTX-M-15)-producing Klebsiella oxytoca ST201 in newborns. Retrieved from https://aem.asm.org/content/early/2019/09/09/AEM.01435-19.

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