title: Comparison of the compact dry TC method with the standard method ISO 21149:2006 for determining aerobic colony counts in cosmetic emulsion.
abstract: OBJECTIVE
  Compact Dry TC, a rapid method kit for determining aerobic colony counts, has been developed by Nissui Pharmaceutical Co. for food application. These plates are pre-sterilized and contain culture medium, a cold-soluble gelling agent and a colour redox indicator for rapid enumeration. In this study, the alternative method is compared with the standard method ISO 21149:2006 - Cosmetic - Microbiology - Enumeration and detection of aerobic mesophilic bacteria, for cosmetic emulsions application.
  
  
  METHODS
  An oil-in-water (o/w) cosmetic emulsion was contaminated with a pool of bacterial strains (Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 6538 and Pseudomonas aeruginosa ATCC 9027). One millilitre of samples was spread on agar as described in ISO 21149. The colonies were enumerated after 3 days of incubation. At the same time, 1.2 mL samples were spread on Compact Dry TC kits. The kit was incubated at 35°C ± 1°C for 48 h, and the colonies were enumerated. Accuracy determination was carried out using six replicates at four levels of concentrations (10, 50, 100 and 250 CFU mL-1). The repeatability study was carried out using 12 replicates at four levels of concentrations (10, 50, 100 and 250 CFU mL-1). Variations relative to the analyst and to the batch of emulsion have been investigated.
  
  
  RESULTS
  The linear correlation coefficients of Compact Dry TC Kit enumeration with standard method ISO 21149:2006 was 0.9999. In comparison study, no apparent differences were noted between the Compact Dry TC kit and the reference method ISO 21149, for the detection level of aerobic microorganisms. Relative accuracy, repeatability and intermediate precision studies were acceptable. In the repeatability study, the Shapiro-Wilk test has confirmed the normally distribution of the twelve assays. No significant variations in Compact Dry TC count results were observed with different analysts and different batches of emulsion.
  
  
  CONCLUSIONS
  The results showed that the two compared methods 'Compact Dry TC' vs. 'conventional pour plate' performed equally well. Demonstration was achieved that the Compact Dry TC method may constitute a useful alternative tool for rapid enumeration of aerobic mesophilic bacteria in cosmetic emulsions.
authors.affiliation: EXPERTOX Agency and Laboratory, 14 rue Godefroy Cavaignac, Paris, 75011, France.|Laboratoire de Chimie Moléculaire, UMR-9168, Ecole Polytechnique, Palaiseau Cedex, 91128, France.
authors.forename: S
authors.initials: S
authors.lastname: De Vaugelade
authors.affiliation: EXPERTOX Agency and Laboratory, 14 rue Godefroy Cavaignac, Paris, 75011, France.
authors.forename: M
authors.initials: M
authors.lastname: Aime
authors.affiliation: BIOPRESERV, Grasse, 06130, France.
authors.forename: N
authors.initials: N
authors.lastname: Farcette
authors.affiliation: BIOPRESERV, Grasse, 06130, France.
authors.forename: E
authors.initials: E
authors.lastname: Maurel
authors.affiliation: BIOPRESERV, Grasse, 06130, France.
authors.forename: T
authors.initials: T
authors.lastname: Lacour
authors.affiliation: EXPERTOX Agency and Laboratory, 14 rue Godefroy Cavaignac, Paris, 75011, France.
authors.forename: C
authors.initials: C
authors.lastname: Thomas
authors.affiliation: Laboratoire de Chimie Moléculaire, UMR-9168, Ecole Polytechnique, Palaiseau Cedex, 91128, France.
authors.forename: S
authors.initials: S
authors.lastname: Bouchonnet
authors.affiliation: EXPERTOX Agency and Laboratory, 14 rue Godefroy Cavaignac, Paris, 75011, France.
authors.forename: S
authors.initials: S
authors.lastname: Pirnay
mesh_terms: D015169:Colony Count, Microbial; D003358:Cosmetics; D004655:Emulsions; D010084:Oxidation-Reduction
chemical_list: D003358:Cosmetics; D004655:Emulsions
keywords: aerobic bacteria; cosmetics; dry culture media; rapid detection