Aims: The absence of objectionable micro-organisms in cosmetics and the efficiency of preservatives are still mainly assessed by time-consuming cultivation-based methods. We explored the applicability of real-time quantitative polymerase chain reaction (qPCR) and reported on the behaviour of different bacteria in artificially contaminated creams.
Methods and results: Real-time qPCR on DNA from Burkholderia cepacia, Pluribacter gergoviae, Pseudomonas aeruginosa and Sphingomonas paucimobilis identified specific primer pairs that amplify accurately and efficiently two strains/isolates of each species. Using DNeasy mericon Food Kit, we detected bacterial growth in an inoculated cosmetic cream and persistency of DNA from heat-inactivated bacteria. We were also able to monitor the growth inhibitory effect of caprylyl glycol and EDTA, also showing how different bacterial species interact depending on the presence/absence of these ingredients. Finally, creams supplemented with the protective cosmetic ingredients revealed the various behaviour of five strains/isolates from P. aeruginosa.
Conclusions: Successfully extracting bacterial DNA from artificially contaminated cosmetic creams, we could perform real-time qPCR to identify and follow the growth of various strains of 4 bacteria species under different conditions.
Significance and impact of the study: Real-time qPCR appears as a promising method to detect bacterial contamination in cosmetic creams and/or to monitor growth inhibition by ingredients.
Keywords: antimicrobial activity; bacteria; cosmetic cream; microbial assay; real-time quantitative PCR.
© 2021 Society for Applied Microbiology.