Survival of E.coli K12 on laboratory coats made of 100% cotton

Abstract

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The research presented in this report focusses on the survival of E.coli K12 bacteria on laboratory coats made of 100% cotton. Therefore aliquots of cultures were applied to small pieces cut from a lab coat, which were then dried in a safety cabinet. Viable E.coli K12 bacteria could be reisolated from such a piece of cloth with high efficiency by incubating it for 5 minutes in either saline or tap water at 35 degr. C. Optimal results were however obtained by incubation for 90 minutes in saline at room temperatures, which became the standard reisolation procedure. In this way, viable bacteria of E.coli K12 strain KMBL1164 could be reisolated till at least twenty days after application and drying. Survival of strain KMBL1164 was not influenced by the number of viable bacteria present in the culture or the presence of additional DNA in the form of plasmid pMP92, which is 7.2 kb in size. Survival was however influenced by the quantity of culture applied, the culturing phase at the moment of application and the chromosomal background of the bacteria applied. Furthermore E.coli K12 strain KMBL1164 survived drying on a piece of a lab coat about as well as a wild type E.coli strain isolated from faeces or E.coli type B and C strains. The first step in the commercial washing procedure of lab coats can consist of rinsing them in water at 35 degr. C. This water is then discharged into the sewage system. Since they undergo no special treatment before they are washed, our results indicate that (genetically modified-) E.coli K12 bacteria can be released into the sewage system during the washing procedure of lab coats worn by workers in recombinant DNA laboratoris. Several other ways in which genetically modified E.coli K12 strains can be released from the laboratory space are discussed.