Investigators
have identified a washing machine as a reservoir of multidrug-resistant
pathogens. The pathogens, a single clone of Klebsiella
oxytoca, were transmitted repeatedly to newborns in a neonatal intensive
care unit at a children's hospital. The transmission was stopped only when the
washing machine was removed from the hospital.
The
research has implications for household use of washers. Water temperatures used
in home washers have been declining, to save energy, to well below 60°C
(140°F), rendering them less lethal to pathogens. Resistance genes, as well as
different microorganisms, can persist in domestic washing machines at those
reduced temperatures, according to the report.
At
the hospital where the washing machine transmitted K. oxytoca, standard
screening procedures revealed the presence of the pathogens on infants in the
ICU. The researchers ultimately traced the source of the pathogens to the
washing machine, after they had failed to find contamination in the incubators
or to find carriers among healthcare workers who came into contact with the
infants.
The
newborns were in the ICU due mostly to premature birth or unrelated
infection.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.
The
investigators assume 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," implicating the
design of the washers, as well as the low heat, according to the report. The
study implies 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.
However,
it still remains unclear how, and via what source the pathogens got into the
washing machine. The infants in the intensive care units (ICU) were colonized,
but not infected by K. oxytoca.
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology
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