The washing machine as a reservoir for transmission of ESBL-producing Klebsiella oxytoca in newborns

During the period from April 2012 to May 2013, 13 newborns and one child in a paediatric hospital ward in Germany were found to be colonised with a distinct clinical clone of an (extended spectrum β-lactamase) (ESBL)-producing Klebsiella oxytoca. This clone was specific to this hospital and had not been previously isolated in Germany. A source-tracking analysis was carried out to identify the source and transmission pathways of the ESBL-producing K. oxytoca clone. A systematic environmental survey of the ward and an audit of the procedures for cleaning and disinfecting surfaces, instruments, incubators, and washing machines was performed. Microbiological samples were obtained from environmental surfaces. Risk factors were analysed for epidemiological linkage. Isolates of an ESBL-producing K. oxytoca were found in the detergent drawer and on the rubber door seal of a washing machine and in two sinks. These strains were typed by pulsed-field-gel-electrophoresis (PFGE) and compared with the isolates from the newborns and their clothing and found to be identical. The retrospective analysis demonstrated that only newborns who had worn clothes that had been washed in the washing machine were colonised with the identical clone. After the washing machine was taken out of use, no further cases were detected over the following 4-year period. We conclude that washing machines are potential reservoirs and vectors for transmission of Enterobacteriaceae, and likely other bacteria.