Impact of freeze/thaw cycles and single freezing at -80 °C on the viability of aerobic bacteria from rectal swabs performed with the ESwabTM system.

The testing of bacterial preservation should be included in preliminary studies to epidemiological studies. In the case of multidrug-resistant organism (MDRO) studies, quantifications of the bacteria make it possible to understand their emergence. The purpose of this preliminary study was to evaluate the performance of ESwabTM on survival of Escherichia coli, Klebsiella pneumoniae, and Enterococcus faecalis, based on the number of freezing and thawing (F/T) cycles at -80 °C and freezing time. A first experiment with 9 samples showed that multiple F/T cycles drastically affected Enterobacteriaceae viabilities and less E. faecalis one. A single freezing maintained the three species viabilities during three weeks. A second experiment showed that E. coli survival was maintained with a 3-month single freezing. This study which used a limited number of bacterial isolates is however a proof of concept establishing the utility of ESwabTM samples when frozen once in quantitative studies of bacteria.