Occurrence of mercury‐resistant Pseudomonas in emulsion formulations preserved with phenylmercuric acetate

Abstract

Synopsis The occurence of mercury-resistant pseudomonads in a seemingly well-preserved toiletry formulation is reported. Microorganisms identified as presumptive Pseudomonas aeruginosa have been isolated from a water-in-oil emulsion despite the inclusion of 0.007%phenylmercuric acetate (PMA) as preservative and also from an emulsion containing 0.002% PMA. Pseudomonads were capable of surviving in these emulsions for up to 3 and 12 months respectively. Culture studies confirmed that the isolates were initially resistant to maximum levels of PMA permitted in shampoos and hair creams according to EEC regulations. Microbial resistance of this nature emphasises the importance of strict attention to plant hygiene and good manufacturing practice.

A rapid method for the evaluation of both extrinsic and intrinsic contamination and resulting spoilage of water-in-oil emulsions

“…(Keammerer et al. 1983) and pseudomonads have been shown to spoil a w/o emulsion in spite of preservation with phenylmercuric acetate (Dixon and Dolan 1981).…”

“…Parenteral nutrition formulations have been reported as physically spoiled by the growth of Pseudomonas aeruginosa, Escherichia coli and, to a lesser degree, Staphylococcus spp. (Keammerer et al 1983) and pseudomonads have been shown to spoil a w/o emulsion in spite of preservation with phenylmercuric acetate (Dixon and Dolan 1981).…”