The recovery of bacteria from white soft paraffin

Abstract

Methods have been investigated for isolating and enumerating, by a membrane filtration technique, E. coli inoculated into white soft paraffin. Of three solvents used to prepare the ointment base for filtration, the best recovery (54%) was obtained with light liquid paraffin. Superior recovery levels (ca 75%) were obtained by homogenizing the ointment base with a Tween 80/peptone water mixture. Recovery levels were greatly affected by the weight of ointment base taken but the Tween 80/peptone water system permitted the estimation of the contamination in up to 0ṁ25 g of white soft paraffin.